Android教程網
  1. 首頁
  2. Android 技術
  3. Android 手機
  4. Android 系統教程
  5. Android 游戲
 Android教程網 >> Android技術 >> 關於Android編程 >> Android之本地緩存——LruCache(內存緩存)與DiskLruCache(硬盤緩存)統一框架

Android之本地緩存——LruCache(內存緩存)與DiskLruCache(硬盤緩存)統一框架

編輯:關於Android編程

一、前言

該框架或者說庫,主要是用於本地的圖片緩存處理。

數據的存入

當你取到圖片的元數據,會將數據存入硬盤緩存以及內存緩存中。

數據的獲取

取數據的時候,先從內存緩存中取;

如果沒有取到,則從硬盤緩存中取(此時如果硬盤緩存有數據,硬盤緩存會重新將數據寫入內存緩存中);

如果硬盤緩存中沒有取到,則從網上重新獲取元數據;

二、設計

根據以上提到的功能:

首先,我們對LruCache以及DiskLruCache分別做了一個管理類,分別命名為LruCacheManager、DiskLruCacheManager,類中對用戶可能用到的方法做封裝;

其次,需要一個統一管理來CacheManager,對LruCacheManager、DiskLruCacheManager中的方法做調度;

三、具體實現

1、內存緩存管理——LruCacheManager

先貼代碼,有個直觀認識:

package com.utils.cache;

import android.graphics.Bitmap;
import android.support.v4.util.LruCache;

public class LruCacheManager {
   
	private LruCache lruCache;
	public LruCacheManager(){
		this((int)Runtime.getRuntime().maxMemory()/1024/8);
	}
	//設置自定義大小的LruCache
	public LruCacheManager(int maxSize){
		lruCache=new LruCache(maxSize*1024){

			@Override
			protected int sizeOf(String key, Bitmap value) {
				return value.getByteCount()/1024;
			}
			
		};
	}
    /**
     * 寫入索引key對應的緩存
     * @param key 索引
     * @param bitmap 緩存內容
     * @return 寫入結果
     */
	public Bitmap putCache(String key,Bitmap bitmap){
		Bitmap bitmapValue=getCache(key);
		if(bitmapValue==null){
			if(lruCache!=null&&bitmap!=null)
			bitmapValue= lruCache.put(key, bitmap);
		}
		return bitmapValue;
	}
	/**
	 * 獲取緩存
	 * @param key 索引key對應的緩存
	 * @return  緩存
	 */
	public Bitmap getCache(String key){ 
		if(lruCache!=null){
			return lruCache.get(key);
		}
		return null;
	}
	
	public void deleteCache(){
		if(lruCache!=null)
		lruCache.evictAll();
	}
	
	public void removeCache(String key){
		if(lruCache!=null)
		lruCache.remove(key);
	}
	
	public int size(){
		int size=0;
		if(lruCache!=null)
			size+=lruCache.size();
		return size;
	}
}
該類是依賴於Android提供的LruCache類實現的。

 

在該類中,提供了兩個構造方法,默認的構造方法是給內存緩存分配當前android操作系統分配給該app的內存的1/8。這話比較拗口,意識就是,如果操作系統分配給app的內存是96M,那麼默認構造方法就是給內存緩存分配內存96/8M。另一個構造方法是讓用戶自定義內存緩存大小。

該類中其他的方法就不多做解釋,都是對LruCache方法的一次封裝。

2、硬盤緩存管理——DiskLruCacheManager

使用硬盤緩存管理前,需要先下載一個開源類:DiskLruCache,如下:

/*  
 * Copyright (C) 2011 The Android Open Source Project  
 *  
 * Licensed under the Apache License, Version 2.0 (the "License");  
 * you may not use this file except in compliance with the License.  
 * You may obtain a copy of the License at  
 *  
 *      http://www.apache.org/licenses/LICENSE-2.0  
 *  
 * Unless required by applicable law or agreed to in writing, software  
 * distributed under the License is distributed on an "AS IS" BASIS,  
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  
 * See the License for the specific language governing permissions and  
 * limitations under the License.  
 */  
  
package com.utils.cache;  
  
import java.io.BufferedInputStream;  
import java.io.BufferedWriter;  
import java.io.Closeable;  
import java.io.EOFException;  
import java.io.File;  
import java.io.FileInputStream;  
import java.io.FileNotFoundException;  
import java.io.FileOutputStream;  
import java.io.FileWriter;  
import java.io.FilterOutputStream;  
import java.io.IOException;  
import java.io.InputStream;  
import java.io.InputStreamReader;  
import java.io.OutputStream;  
import java.io.OutputStreamWriter;  
import java.io.Reader;  
import java.io.StringWriter;  
import java.io.Writer;  
import java.lang.reflect.Array;  
import java.nio.charset.Charset;  
import java.util.ArrayList;  
import java.util.Arrays;  
import java.util.Iterator;  
import java.util.LinkedHashMap;  
import java.util.Map;  
import java.util.concurrent.Callable;  
import java.util.concurrent.ExecutorService;  
import java.util.concurrent.LinkedBlockingQueue;  
import java.util.concurrent.ThreadPoolExecutor;  
import java.util.concurrent.TimeUnit;  
  
/**  
 ******************************************************************************  
 * Taken from the JB source code, can be found in:  
 * libcore/luni/src/main/java/libcore/io/DiskLruCache.java  
 * or direct link:  
 * https://android.googlesource.com/platform/libcore/+/android-4.1.1_r1/luni/src/main/java/libcore/io/DiskLruCache.java  
 ******************************************************************************  
 *  
 * A cache that uses a bounded amount of space on a filesystem. Each cache  
 * entry has a string key and a fixed number of values. Values are byte  
 * sequences, accessible as streams or files. Each value must be between {@code  
 * 0} and {@code Integer.MAX_VALUE} bytes in length.  
 *  
 * <p>The cache stores its data in a directory on the filesystem. This  
 * directory must be exclusive to the cache; the cache may delete or overwrite  
 * files from its directory. It is an error for multiple processes to use the  
 * same cache directory at the same time.  
 *  
 * <p>This cache limits the number of bytes that it will store on the  
 * filesystem. When the number of stored bytes exceeds the limit, the cache will  
 * remove entries in the background until the limit is satisfied. The limit is  
 * not strict: the cache may temporarily exceed it while waiting for files to be  
 * deleted. The limit does not include filesystem overhead or the cache  
 * journal so space-sensitive applications should set a conservative limit.  
 *  
 * <p>Clients call {@link #edit} to create or update the values of an entry. An  
 * entry may have only one editor at one time; if a value is not available to be  
 * edited then {@link #edit} will return null.  
 * <ul>  
 *     <li>When an entry is being <strong>created</strong> it is necessary to  
 *         supply a full set of values; the empty value should be used as a  
 *         placeholder if necessary.  
 *     <li>When an entry is being <strong>edited</strong>, it is not necessary  
 *         to supply data for every value; values default to their previous  
 *         value.  
 * </ul>  
 * Every {@link #edit} call must be matched by a call to {@link Editor#commit}  
 * or {@link Editor#abort}. Committing is atomic: a read observes the full set  
 * of values as they were before or after the commit, but never a mix of values.  
 *  
 * <p>Clients call {@link #get} to read a snapshot of an entry. The read will  
 * observe the value at the time that {@link #get} was called. Updates and  
 * removals after the call do not impact ongoing reads.  
 *  
 * <p>This class is tolerant of some I/O errors. If files are missing from the  
 * filesystem, the corresponding entries will be dropped from the cache. If  
 * an error occurs while writing a cache value, the edit will fail silently.  
 * Callers should handle other problems by catching {@code IOException} and  
 * responding appropriately.  
 */  
public final class DiskLruCache implements Closeable {  
    static final String JOURNAL_FILE = "journal";  
    static final String JOURNAL_FILE_TMP = "journal.tmp";  
    static final String MAGIC = "libcore.io.DiskLruCache";  
    static final String VERSION_1 = "1";  
    static final long ANY_SEQUENCE_NUMBER = -1;  
    private static final String CLEAN = "CLEAN";  
    private static final String DIRTY = "DIRTY";  
    private static final String REMOVE = "REMOVE";  
    private static final String READ = "READ";  
  
    private static final Charset UTF_8 = Charset.forName("UTF-8");  
    private static final int IO_BUFFER_SIZE = 8 * 1024;  
  
    /*  
     * This cache uses a journal file named "journal". A typical journal file  
     * looks like this:  
     *     libcore.io.DiskLruCache  
     *     1  
     *     100  
     *     2  
     *  
     *     CLEAN 3400330d1dfc7f3f7f4b8d4d803dfcf6 832 21054  
     *     DIRTY 335c4c6028171cfddfbaae1a9c313c52  
     *     CLEAN 335c4c6028171cfddfbaae1a9c313c52 3934 2342  
     *     REMOVE 335c4c6028171cfddfbaae1a9c313c52  
     *     DIRTY 1ab96a171faeeee38496d8b330771a7a  
     *     CLEAN 1ab96a171faeeee38496d8b330771a7a 1600 234  
     *     READ 335c4c6028171cfddfbaae1a9c313c52  
     *     READ 3400330d1dfc7f3f7f4b8d4d803dfcf6  
     *  
     * The first five lines of the journal form its header. They are the  
     * constant string "libcore.io.DiskLruCache", the disk cache's version,  
     * the application's version, the value count, and a blank line.  
     *  
     * Each of the subsequent lines in the file is a record of the state of a  
     * cache entry. Each line contains space-separated values: a state, a key,  
     * and optional state-specific values.  
     *   o DIRTY lines track that an entry is actively being created or updated.  
     *     Every successful DIRTY action should be followed by a CLEAN or REMOVE  
     *     action. DIRTY lines without a matching CLEAN or REMOVE indicate that  
     *     temporary files may need to be deleted.  
     *   o CLEAN lines track a cache entry that has been successfully published  
     *     and may be read. A publish line is followed by the lengths of each of  
     *     its values.  
     *   o READ lines track accesses for LRU.  
     *   o REMOVE lines track entries that have been deleted.  
     *  
     * The journal file is appended to as cache operations occur. The journal may  
     * occasionally be compacted by dropping redundant lines. A temporary file named  
     * "journal.tmp" will be used during compaction; that file should be deleted if  
     * it exists when the cache is opened.  
     */  
  
    private final File directory;  
    private final File journalFile;  
    private final File journalFileTmp;  
    private final int appVersion;  
    private final long maxSize;  
    private final int valueCount;  
    private long size = 0;  
    private Writer journalWriter;  
    private final LinkedHashMap<String, Entry> lruEntries  
            = new LinkedHashMap<String, Entry>(0, 0.75f, true);  
    private int redundantOpCount;  
  
    /**  
     * To differentiate between old and current snapshots, each entry is given  
     * a sequence number each time an edit is committed. A snapshot is stale if  
     * its sequence number is not equal to its entry's sequence number.  
     */  
    private long nextSequenceNumber = 0;  
  
    /* From java.util.Arrays */  
    @SuppressWarnings("unchecked")  
    private static <T> T[] copyOfRange(T[] original, int start, int end) {  
        final int originalLength = original.length; // For exception priority compatibility.  
        if (start > end) {  
            throw new IllegalArgumentException();  
        }  
        if (start < 0 || start > originalLength) {  
            throw new ArrayIndexOutOfBoundsException();  
        }  
        final int resultLength = end - start;  
        final int copyLength = Math.min(resultLength, originalLength - start);  
        final T[] result = (T[]) Array  
                .newInstance(original.getClass().getComponentType(), resultLength);  
        System.arraycopy(original, start, result, 0, copyLength);  
        return result;  
    }  
  
    /**  
     * Returns the remainder of 'reader' as a string, closing it when done.  
     */  
    public static String readFully(Reader reader) throws IOException {  
        try {  
            StringWriter writer = new StringWriter();  
            char[] buffer = new char[1024];  
            int count;  
            while ((count = reader.read(buffer)) != -1) {  
                writer.write(buffer, 0, count);  
            }  
            return writer.toString();  
        } finally {  
            reader.close();  
        }  
    }  
  
    /**  
     * Returns the ASCII characters up to but not including the next "\r\n", or  
     * "\n".  
     *  
     * @throws java.io.EOFException if the stream is exhausted before the next newline  
     *     character.  
     */  
    public static String readAsciiLine(InputStream in) throws IOException {  
        // TODO: support UTF-8 here instead  
  
        StringBuilder result = new StringBuilder(80);  
        while (true) {  
            int c = in.read();  
            if (c == -1) {  
                throw new EOFException();  
            } else if (c == '\n') {  
                break;  
            }  
  
            result.append((char) c);  
        }  
        int length = result.length();  
        if (length > 0 && result.charAt(length - 1) == '\r') {  
            result.setLength(length - 1);  
        }  
        return result.toString();  
    }  
  
    /**  
     * Closes 'closeable', ignoring any checked exceptions. Does nothing if 'closeable' is null.  
     */  
    public static void closeQuietly(Closeable closeable) {  
        if (closeable != null) {  
            try {  
                closeable.close();  
            } catch (RuntimeException rethrown) {  
                throw rethrown;  
            } catch (Exception ignored) {  
            }  
        }  
    }  
  
    /**  
     * Recursively delete everything in {@code dir}.  
     */  
    // TODO: this should specify paths as Strings rather than as Files  
    public static void deleteContents(File dir) throws IOException {  
        File[] files = dir.listFiles();  
        if (files == null) {  
            throw new IllegalArgumentException("not a directory: " + dir);  
        }  
        for (File file : files) {  
            if (file.isDirectory()) {  
                deleteContents(file);  
            }  
            if (!file.delete()) {  
                throw new IOException("failed to delete file: " + file);  
            }  
        }  
    }  
  
    /** This cache uses a single background thread to evict entries. */  
    private final ExecutorService executorService = new ThreadPoolExecutor(0, 1,  
            60L, TimeUnit.SECONDS, new LinkedBlockingQueue<Runnable>());  
    private final Callable<Void> cleanupCallable = new Callable<Void>() {  
        @Override public Void call() throws Exception {  
            synchronized (DiskLruCache.this) {  
                if (journalWriter == null) {  
                    return null; // closed  
                }  
                trimToSize();  
                if (journalRebuildRequired()) {  
                    rebuildJournal();  
                    redundantOpCount = 0;  
                }  
            }  
            return null;  
        }  
    };  
  
    private DiskLruCache(File directory, int appVersion, int valueCount, long maxSize) {  
        this.directory = directory;  
        this.appVersion = appVersion;  
        this.journalFile = new File(directory, JOURNAL_FILE);  
        this.journalFileTmp = new File(directory, JOURNAL_FILE_TMP);  
        this.valueCount = valueCount;  
        this.maxSize = maxSize;  
    }  
  
    /**  
     * Opens the cache in {@code directory}, creating a cache if none exists  
     * there.  
     *  
     * @param directory a writable directory  
     * @param appVersion  
     * @param valueCount the number of values per cache entry. Must be positive.  
     * @param maxSize the maximum number of bytes this cache should use to store  
     * @throws java.io.IOException if reading or writing the cache directory fails  
     */  
    public static DiskLruCache open(File directory, int appVersion, int valueCount, long maxSize)  
            throws IOException {  
        if (maxSize <= 0) {  
            throw new IllegalArgumentException("maxSize <= 0");  
        }  
        if (valueCount <= 0) {  
            throw new IllegalArgumentException("valueCount <= 0");  
        }  
  
        // prefer to pick up where we left off  
        DiskLruCache cache = new DiskLruCache(directory, appVersion, valueCount, maxSize);  
        if (cache.journalFile.exists()) {  
            try {  
                cache.readJournal();  
                cache.processJournal();  
                cache.journalWriter = new BufferedWriter(new FileWriter(cache.journalFile, true),  
                        IO_BUFFER_SIZE);  
                return cache;  
            } catch (IOException journalIsCorrupt) {  
//                System.logW("DiskLruCache " + directory + " is corrupt: "  
//                        + journalIsCorrupt.getMessage() + ", removing");  
                cache.delete();  
            }  
        }  
  
        // create a new empty cache  
        directory.mkdirs();  
        cache = new DiskLruCache(directory, appVersion, valueCount, maxSize);  
        cache.rebuildJournal();  
        return cache;  
    }  
  
    private void readJournal() throws IOException {  
        InputStream in = new BufferedInputStream(new FileInputStream(journalFile), IO_BUFFER_SIZE);  
        try {  
            String magic = readAsciiLine(in);  
            String version = readAsciiLine(in);  
            String appVersionString = readAsciiLine(in);  
            String valueCountString = readAsciiLine(in);  
            String blank = readAsciiLine(in);  
            if (!MAGIC.equals(magic)  
                    || !VERSION_1.equals(version)  
                    || !Integer.toString(appVersion).equals(appVersionString)  
                    || !Integer.toString(valueCount).equals(valueCountString)  
                    || !"".equals(blank)) {  
                throw new IOException("unexpected journal header: ["  
                        + magic + ", " + version + ", " + valueCountString + ", " + blank + "]");  
            }  
  
            while (true) {  
                try {  
                    readJournalLine(readAsciiLine(in));  
                } catch (EOFException endOfJournal) {  
                    break;  
                }  
            }  
        } finally {  
            closeQuietly(in);  
        }  
    }  
  
    private void readJournalLine(String line) throws IOException {  
        String[] parts = line.split(" ");  
        if (parts.length < 2) {  
            throw new IOException("unexpected journal line: " + line);  
        }  
  
        String key = parts[1];  
        if (parts[0].equals(REMOVE) && parts.length == 2) {  
            lruEntries.remove(key);  
            return;  
        }  
  
        Entry entry = lruEntries.get(key);  
        if (entry == null) {  
            entry = new Entry(key);  
            lruEntries.put(key, entry);  
        }  
  
        if (parts[0].equals(CLEAN) && parts.length == 2 + valueCount) {  
            entry.readable = true;  
            entry.currentEditor = null;  
            entry.setLengths(copyOfRange(parts, 2, parts.length));  
        } else if (parts[0].equals(DIRTY) && parts.length == 2) {  
            entry.currentEditor = new Editor(entry);  
        } else if (parts[0].equals(READ) && parts.length == 2) {  
            // this work was already done by calling lruEntries.get()  
        } else {  
            throw new IOException("unexpected journal line: " + line);  
        }  
    }  
  
    /**  
     * Computes the initial size and collects garbage as a part of opening the  
     * cache. Dirty entries are assumed to be inconsistent and will be deleted.  
     */  
    private void processJournal() throws IOException {  
        deleteIfExists(journalFileTmp);  
        for (Iterator<Entry> i = lruEntries.values().iterator(); i.hasNext(); ) {  
            Entry entry = i.next();  
            if (entry.currentEditor == null) {  
                for (int t = 0; t < valueCount; t++) {  
                    size += entry.lengths[t];  
                }  
            } else {  
                entry.currentEditor = null;  
                for (int t = 0; t < valueCount; t++) {  
                    deleteIfExists(entry.getCleanFile(t));  
                    deleteIfExists(entry.getDirtyFile(t));  
                }  
                i.remove();  
            }  
        }  
    }  
  
    /**  
     * Creates a new journal that omits redundant information. This replaces the  
     * current journal if it exists.  
     */  
    private synchronized void rebuildJournal() throws IOException {  
        if (journalWriter != null) {  
            journalWriter.close();  
        }  
  
        Writer writer = new BufferedWriter(new FileWriter(journalFileTmp), IO_BUFFER_SIZE);  
        writer.write(MAGIC);  
        writer.write("\n");  
        writer.write(VERSION_1);  
        writer.write("\n");  
        writer.write(Integer.toString(appVersion));  
        writer.write("\n");  
        writer.write(Integer.toString(valueCount));  
        writer.write("\n");  
        writer.write("\n");  
  
        for (Entry entry : lruEntries.values()) {  
            if (entry.currentEditor != null) {  
                writer.write(DIRTY + ' ' + entry.key + '\n');  
            } else {  
                writer.write(CLEAN + ' ' + entry.key + entry.getLengths() + '\n');  
            }  
        }  
  
        writer.close();  
        journalFileTmp.renameTo(journalFile);  
        journalWriter = new BufferedWriter(new FileWriter(journalFile, true), IO_BUFFER_SIZE);  
    }  
  
    private static void deleteIfExists(File file) throws IOException {  
//        try {  
//            Libcore.os.remove(file.getPath());  
//        } catch (ErrnoException errnoException) {  
//            if (errnoException.errno != OsConstants.ENOENT) {  
//                throw errnoException.rethrowAsIOException();  
//            }  
//        }  
        if (file.exists() && !file.delete()) {  
            throw new IOException();  
        }  
    }  
  
    /**  
     * Returns a snapshot of the entry named {@code key}, or null if it doesn't  
     * exist is not currently readable. If a value is returned, it is moved to  
     * the head of the LRU queue.  
     */  
    public synchronized Snapshot get(String key) throws IOException {  
        checkNotClosed();  
        validateKey(key);  
        Entry entry = lruEntries.get(key);  
        if (entry == null) {  
            return null;  
        }  
  
        if (!entry.readable) {  
            return null;  
        }  
  
        /*  
         * Open all streams eagerly to guarantee that we see a single published  
         * snapshot. If we opened streams lazily then the streams could come  
         * from different edits.  
         */  
        InputStream[] ins = new InputStream[valueCount];  
        try {  
            for (int i = 0; i < valueCount; i++) {  
                ins[i] = new FileInputStream(entry.getCleanFile(i));  
            }  
        } catch (FileNotFoundException e) {  
            // a file must have been deleted manually!  
            return null;  
        }  
  
        redundantOpCount++;  
        journalWriter.append(READ + ' ' + key + '\n');  
        if (journalRebuildRequired()) {  
            executorService.submit(cleanupCallable);  
        }  
  
        return new Snapshot(key, entry.sequenceNumber, ins);  
    }  
  
    /**  
     * Returns an editor for the entry named {@code key}, or null if another  
     * edit is in progress.  
     */  
    public Editor edit(String key) throws IOException {  
        return edit(key, ANY_SEQUENCE_NUMBER);  
    }  
  
    private synchronized Editor edit(String key, long expectedSequenceNumber) throws IOException {  
        checkNotClosed();  
        validateKey(key);  
        Entry entry = lruEntries.get(key);  
        if (expectedSequenceNumber != ANY_SEQUENCE_NUMBER  
                && (entry == null || entry.sequenceNumber != expectedSequenceNumber)) {  
            return null; // snapshot is stale  
        }  
        if (entry == null) {  
            entry = new Entry(key);  
            lruEntries.put(key, entry);  
        } else if (entry.currentEditor != null) {  
            return null; // another edit is in progress  
        }  
  
        Editor editor = new Editor(entry);  
        entry.currentEditor = editor;  
  
        // flush the journal before creating files to prevent file leaks  
        journalWriter.write(DIRTY + ' ' + key + '\n');  
        journalWriter.flush();  
        return editor;  
    }  
  
    /**  
     * Returns the directory where this cache stores its data.  
     */  
    public File getDirectory() {  
        return directory;  
    }  
  
    /**  
     * Returns the maximum number of bytes that this cache should use to store  
     * its data.  
     */  
    public long maxSize() {  
        return maxSize;  
    }  
  
    /**  
     * Returns the number of bytes currently being used to store the values in  
     * this cache. This may be greater than the max size if a background  
     * deletion is pending.  
     */  
    public synchronized long size() {  
        return size;  
    }  
  
    private synchronized void completeEdit(Editor editor, boolean success) throws IOException {  
        Entry entry = editor.entry;  
        if (entry.currentEditor != editor) {  
            throw new IllegalStateException();  
        }  
  
        // if this edit is creating the entry for the first time, every index must have a value  
        if (success && !entry.readable) {  
            for (int i = 0; i < valueCount; i++) {  
                if (!entry.getDirtyFile(i).exists()) {  
                    editor.abort();  
                    throw new IllegalStateException("edit didn't create file " + i);  
                }  
            }  
        }  
  
        for (int i = 0; i < valueCount; i++) {  
            File dirty = entry.getDirtyFile(i);  
            if (success) {  
                if (dirty.exists()) {  
                    File clean = entry.getCleanFile(i);  
                    dirty.renameTo(clean);  
                    long oldLength = entry.lengths[i];  
                    long newLength = clean.length();  
                    entry.lengths[i] = newLength;  
                    size = size - oldLength + newLength;  
                }  
            } else {  
                deleteIfExists(dirty);  
            }  
        }  
  
        redundantOpCount++;  
        entry.currentEditor = null;  
        if (entry.readable | success) {  
            entry.readable = true;  
            journalWriter.write(CLEAN + ' ' + entry.key + entry.getLengths() + '\n');  
            if (success) {  
                entry.sequenceNumber = nextSequenceNumber++;  
            }  
        } else {  
            lruEntries.remove(entry.key);  
            journalWriter.write(REMOVE + ' ' + entry.key + '\n');  
        }  
  
        if (size > maxSize || journalRebuildRequired()) {  
            executorService.submit(cleanupCallable);  
        }  
    }  
  
    /**  
     * We only rebuild the journal when it will halve the size of the journal  
     * and eliminate at least 2000 ops.  
     */  
    private boolean journalRebuildRequired() {  
        final int REDUNDANT_OP_COMPACT_THRESHOLD = 2000;  
        return redundantOpCount >= REDUNDANT_OP_COMPACT_THRESHOLD  
                && redundantOpCount >= lruEntries.size();  
    }  
  
    /**  
     * Drops the entry for {@code key} if it exists and can be removed. Entries  
     * actively being edited cannot be removed.  
     *  
     * @return true if an entry was removed.  
     */  
    public synchronized boolean remove(String key) throws IOException {  
        checkNotClosed();  
        validateKey(key);  
        Entry entry = lruEntries.get(key);  
        if (entry == null || entry.currentEditor != null) {  
            return false;  
        }  
  
        for (int i = 0; i < valueCount; i++) {  
            File file = entry.getCleanFile(i);  
            if (!file.delete()) {  
                throw new IOException("failed to delete " + file);  
            }  
            size -= entry.lengths[i];  
            entry.lengths[i] = 0;  
        }  
  
        redundantOpCount++;  
        journalWriter.append(REMOVE + ' ' + key + '\n');  
        lruEntries.remove(key);  
  
        if (journalRebuildRequired()) {  
            executorService.submit(cleanupCallable);  
        }  
  
        return true;  
    }  
  
    /**  
     * Returns true if this cache has been closed.  
     */  
    public boolean isClosed() {  
        return journalWriter == null;  
    }  
  
    private void checkNotClosed() {  
        if (journalWriter == null) {  
            throw new IllegalStateException("cache is closed");  
        }  
    }  
  
    /**  
     * Force buffered operations to the filesystem.  
     */  
    public synchronized void flush() throws IOException {  
        checkNotClosed();  
        trimToSize();  
        journalWriter.flush();  
    }  
  
    /**  
     * Closes this cache. Stored values will remain on the filesystem.  
     */  
    public synchronized void close() throws IOException {  
        if (journalWriter == null) {  
            return; // already closed  
        }  
        for (Entry entry : new ArrayList<Entry>(lruEntries.values())) {  
            if (entry.currentEditor != null) {  
                entry.currentEditor.abort();  
            }  
        }  
        trimToSize();  
        journalWriter.close();  
        journalWriter = null;  
    }  
  
    private void trimToSize() throws IOException {  
        while (size > maxSize) {  
//            Map.Entry<String, Entry> toEvict = lruEntries.eldest();  
            final Map.Entry<String, Entry> toEvict = lruEntries.entrySet().iterator().next();  
            remove(toEvict.getKey());  
        }  
    }  
  
    /**  
     * Closes the cache and deletes all of its stored values. This will delete  
     * all files in the cache directory including files that weren't created by  
     * the cache.  
     */  
    public void delete() throws IOException {  
        close();  
        deleteContents(directory);  
    }  
  
    private void validateKey(String key) {  
        if (key.contains(" ") || key.contains("\n") || key.contains("\r")) {  
            throw new IllegalArgumentException(  
                    "keys must not contain spaces or newlines: \"" + key + "\"");  
        }  
    }  
  
    private static String inputStreamToString(InputStream in) throws IOException {  
        return readFully(new InputStreamReader(in, UTF_8));  
    }  
  
    /**  
     * A snapshot of the values for an entry.  
     */  
    public final class Snapshot implements Closeable {  
        private final String key;  
        private final long sequenceNumber;  
        private final InputStream[] ins;  
  
        private Snapshot(String key, long sequenceNumber, InputStream[] ins) {  
            this.key = key;  
            this.sequenceNumber = sequenceNumber;  
            this.ins = ins;  
        }  
  
        /**  
         * Returns an editor for this snapshot's entry, or null if either the  
         * entry has changed since this snapshot was created or if another edit  
         * is in progress.  
         */  
        public Editor edit() throws IOException {  
            return DiskLruCache.this.edit(key, sequenceNumber);  
        }  
  
        /**  
         * Returns the unbuffered stream with the value for {@code index}.  
         */  
        public InputStream getInputStream(int index) {  
            return ins[index];  
        }  
  
        /**  
         * Returns the string value for {@code index}.  
         */  
        public String getString(int index) throws IOException {  
            return inputStreamToString(getInputStream(index));  
        }  
  
        @Override public void close() {  
            for (InputStream in : ins) {  
                closeQuietly(in);  
            }  
        }  
    }  
  
    /**  
     * Edits the values for an entry.  
     */  
    public final class Editor {  
        private final Entry entry;  
        private boolean hasErrors;  
  
        private Editor(Entry entry) {  
            this.entry = entry;  
        }  
  
        /**  
         * Returns an unbuffered input stream to read the last committed value,  
         * or null if no value has been committed.  
         */  
        public InputStream newInputStream(int index) throws IOException {  
            synchronized (DiskLruCache.this) {  
                if (entry.currentEditor != this) {  
                    throw new IllegalStateException();  
                }  
                if (!entry.readable) {  
                    return null;  
                }  
                return new FileInputStream(entry.getCleanFile(index));  
            }  
        }  
  
        /**  
         * Returns the last committed value as a string, or null if no value  
         * has been committed.  
         */  
        public String getString(int index) throws IOException {  
            InputStream in = newInputStream(index);  
            return in != null ? inputStreamToString(in) : null;  
        }  
  
        /**  
         * Returns a new unbuffered output stream to write the value at  
         * {@code index}. If the underlying output stream encounters errors  
         * when writing to the filesystem, this edit will be aborted when  
         * {@link #commit} is called. The returned output stream does not throw  
         * IOExceptions.  
         */  
        public OutputStream newOutputStream(int index) throws IOException {  
            synchronized (DiskLruCache.this) {  
                if (entry.currentEditor != this) {  
                    throw new IllegalStateException();  
                }  
                return new FaultHidingOutputStream(new FileOutputStream(entry.getDirtyFile(index)));  
            }  
        }  
  
        /**  
         * Sets the value at {@code index} to {@code value}.  
         */  
        public void set(int index, String value) throws IOException {  
            Writer writer = null;  
            try {  
                writer = new OutputStreamWriter(newOutputStream(index), UTF_8);  
                writer.write(value);  
            } finally {  
                closeQuietly(writer);  
            }  
        }  
  
        /**  
         * Commits this edit so it is visible to readers.  This releases the  
         * edit lock so another edit may be started on the same key.  
         */  
        public void commit() throws IOException {  
            if (hasErrors) {  
                completeEdit(this, false);  
                remove(entry.key); // the previous entry is stale  
            } else {  
                completeEdit(this, true);  
            }  
        }  
  
        /**  
         * Aborts this edit. This releases the edit lock so another edit may be  
         * started on the same key.  
         */  
        public void abort() throws IOException {  
            completeEdit(this, false);  
        }  
  
        private class FaultHidingOutputStream extends FilterOutputStream {  
            private FaultHidingOutputStream(OutputStream out) {  
                super(out);  
            }  
  
            @Override public void write(int oneByte) {  
                try {  
                    out.write(oneByte);  
                } catch (IOException e) {  
                    hasErrors = true;  
                }  
            }  
  
            @Override public void write(byte[] buffer, int offset, int length) {  
                try {  
                    out.write(buffer, offset, length);  
                } catch (IOException e) {  
                    hasErrors = true;  
                }  
            }  
  
            @Override public void close() {  
                try {  
                    out.close();  
                } catch (IOException e) {  
                    hasErrors = true;  
                }  
            }  
  
            @Override public void flush() {  
                try {  
                    out.flush();  
                } catch (IOException e) {  
                    hasErrors = true;  
                }  
            }  
        }  
    }  
  
    private final class Entry {  
        private final String key;  
  
        /** Lengths of this entry's files. */  
        private final long[] lengths;  
  
        /** True if this entry has ever been published */  
        private boolean readable;  
  
        /** The ongoing edit or null if this entry is not being edited. */  
        private Editor currentEditor;  
  
        /** The sequence number of the most recently committed edit to this entry. */  
        private long sequenceNumber;  
  
        private Entry(String key) {  
            this.key = key;  
            this.lengths = new long[valueCount];  
        }  
  
        public String getLengths() throws IOException {  
            StringBuilder result = new StringBuilder();  
            for (long size : lengths) {  
                result.append(' ').append(size);  
            }  
            return result.toString();  
        }  
  
        /**  
         * Set lengths using decimal numbers like "10123".  
         */  
        private void setLengths(String[] strings) throws IOException {  
            if (strings.length != valueCount) {  
                throw invalidLengths(strings);  
            }  
  
            try {  
                for (int i = 0; i < strings.length; i++) {  
                    lengths[i] = Long.parseLong(strings[i]);  
                }  
            } catch (NumberFormatException e) {  
                throw invalidLengths(strings);  
            }  
        }  
  
        private IOException invalidLengths(String[] strings) throws IOException {  
            throw new IOException("unexpected journal line: " + Arrays.toString(strings));  
        }  
  
        public File getCleanFile(int i) {  
            return new File(directory, key + "." + i);  
        }  
  
        public File getDirtyFile(int i) {  
            return new File(directory, key + "." + i + ".tmp");  
        }  
    }  
}  


針對這個DIskLruCache,也對它做一層封裝,也就是我們的DiskLruCacheManager:

 

package com.utils.cache;

import java.io.File;
import java.io.IOException;
import java.io.OutputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

import com.utils.cache.DiskLruCache.Snapshot;

import android.content.Context;
import android.content.pm.PackageInfo;
import android.content.pm.PackageManager.NameNotFoundException;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Environment;


public  class DiskLruCacheManager {
  
  private static int maxSize=20*1024*1024;
  private  DiskLruCache mDiskLruCache;
  private final static String defaultName="default";
  
  public DiskLruCacheManager(Context context){
	 this(context, defaultName, maxSize);
  }
  public DiskLruCacheManager(Context context,int maxDiskLruCacheSize){
	  this(context, defaultName, maxDiskLruCacheSize);
  }
  public DiskLruCacheManager(Context context,String dirName){
	this(context, dirName, maxSize);
  }
  
  public DiskLruCacheManager(Context context,String dirName,int maxDiskLruCacheSize){
	  try {
		  mDiskLruCache=DiskLruCache.open(getDiskCacheFile(context,dirName), getAppVersion(context), 1, maxDiskLruCacheSize);
	  } catch (IOException e) {
		  e.printStackTrace();
	  }
  }
  /**
   * 獲取文件夾地址,如果不存在,則創建
   * @param context 上下文
   * @param dirName 文件名
   * @return  File 文件
   */
  private  File getDiskCacheFile(Context context,String dirName){
      File cacheDir=packDiskCacheFile(context,dirName);
      if (!cacheDir.exists()) {  
          cacheDir.mkdirs();  
      }  
      return cacheDir;  
  }
  
  /**
   * 獲取文件夾地址
   * @param context 上下文
   * @param dirName 文件名
   * @return File 文件
   */
  private   File packDiskCacheFile(Context context,String dirName){
	  String cachePath;  
      if (Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())  
              || !Environment.isExternalStorageRemovable()) {  
          cachePath = context.getExternalCacheDir().getPath();  
      } else {  
          cachePath = context.getCacheDir().getPath();  
      }  
      return new File(cachePath + File.separator + dirName);  
  }
  
  /** 
   * 獲取當前應用程序的版本號。 
   */  
  private int getAppVersion(Context context) {  
      try {  
          PackageInfo info = context.getPackageManager().getPackageInfo(context.getPackageName(),0);  
          return info.versionCode;  
      } catch (NameNotFoundException e) {  
          e.printStackTrace();  
      }  
      return 1;  
  }  
  
  /** 
   * 使用MD5算法對傳入的key進行加密並返回。 
   */  
  private String Md5(String key) {  
      String cacheKey;  
      try {  
          final MessageDigest mDigest = MessageDigest.getInstance("MD5");  
          mDigest.update(key.getBytes());  
          cacheKey = bytesToHexString(mDigest.digest());  
      } catch (NoSuchAlgorithmException e) {  
          cacheKey = String.valueOf(key.hashCode());  
      }  
      return cacheKey;  
  }  
  
  private String bytesToHexString(byte[] bytes) {  
      StringBuilder sb = new StringBuilder();  
      for (int i = 0; i < bytes.length; i++) {  
          String hex = Integer.toHexString(0xFF & bytes[i]);  
          if (hex.length() == 1) {  
              sb.append('0');  
          }  
          sb.append(hex);  
      }  
      return sb.toString();  
  }  
  /**
   * Bitmap格式數據寫入到outputstream中 
   * @param bm Bitmap數據
   * @param baos outputstream
   * @return outputstream
   */
  private OutputStream Bitmap2OutputStream(Bitmap bm,OutputStream baos) {  
	  if(bm!=null){
	      bm.compress(Bitmap.CompressFormat.PNG, 100, baos);  
	  }
	  return baos;
  }  
  
  /** 
   * 將緩存記錄同步到journal文件中。 
   */  
  public void fluchCache() {  
      if (mDiskLruCache != null) {  
          try {  
              mDiskLruCache.flush();  
          } catch (IOException e) {  
              e.printStackTrace();  
          }  
      }  
  }  

  /**
   * 獲取硬盤緩存
   * @param key 所有
   * @return Bitmap格式緩存
   */
  public Bitmap getDiskCache(String key){
	String md5Key=Md5(key);
    Bitmap bitmap=null;
	try {
		if(mDiskLruCache!=null){
			Snapshot 	snapshot = mDiskLruCache.get(md5Key);
			if(snapshot!=null){
				bitmap=BitmapFactory.decodeStream(snapshot.getInputStream(0)) ;	
			}
		}
	}
	 catch (IOException e) {
			e.printStackTrace();
		}
	  return bitmap;
  }
  
  /**
   * 設置key對應的緩存
   * @param key 索引
   * @param bitmap Bitmap格式數據
   * @return 是否寫入
   */
  public boolean putDiskCache(String key,Bitmap bitmap){
	  String md5Key=Md5(key);
	  try {
		  if(mDiskLruCache!=null){
			    if(mDiskLruCache.get(md5Key)!=null){
			    	return true;
			    }
				DiskLruCache.Editor editor=mDiskLruCache.edit(md5Key);
				if(editor!=null){
					OutputStream outputStream= editor.newOutputStream(0);
					Bitmap2OutputStream(bitmap,outputStream);
					if(outputStream!=null){
						editor.commit();
						return true;
					}
					else {
						editor.abort();
						return false;
					}
				}
		  }
	} catch (IOException e) {
		// TODO Auto-generated catch block
		e.printStackTrace();
	}
	  return false;
  }
  
  public void deleteDiskCache(){
	  try {
		  if(mDiskLruCache!=null){
			  mDiskLruCache.delete();
		  }
	} catch (IOException e) {
		// TODO Auto-generated catch block
		e.printStackTrace();
	}
  }

  public void removeDiskCache(String key){
	  if(mDiskLruCache!=null){
		  try {
			mDiskLruCache.remove(key);
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	  }
  }
  
  public  void deleteFile(Context context,String dirName){
	  try {
			DiskLruCache.deleteContents(packDiskCacheFile(context,dirName));
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
  }
  
  public int size(){
	  int size=0;
	  if(mDiskLruCache!=null){
		  size=(int) mDiskLruCache.size();
	  }
	  return size;
  }
  
  public void close(){
	  if(mDiskLruCache!=null){
		  try {
			mDiskLruCache.close();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	  }
  }
  
}

該封裝類中包含4個構造函數,主要也是用於用戶的自定義,讓用戶可以使用默認設置,以及自定義硬盤緩存的文件夾名稱以及大小。

 

後續的封裝類,是對硬盤緩存的讀寫、大小、移除等功能的封裝。

3、統一的緩存管理類——CacheManager

這個類是對整個緩存的調度類。使用者也只需要接觸這個類即可。CacheManager簡化了內存緩存與硬盤緩存同時使用時的代碼操作。如下:

 

package com.utils.cache;

import android.content.Context;
import android.graphics.Bitmap;
import android.text.TextUtils;

public class CacheManager {
    /**
     * 只使用內存緩存(LruCache)
     */
	public static final int ONLY_LRU=1;
	/**
	 * 只使用硬盤緩存(DiskLruCache)
	 */
	public static final int ONLY_DISKLRU=2;
	/**
	 * 同時使用內存緩存(LruCache)與硬盤緩存(DiskLruCache)
	 */
	public static final int ALL_ALLOW=0;
	
	/**
	 * 設置類型為硬盤緩存——用於取硬盤緩存大小
	 */
	public static final int DISKSIZE=0;
	/**
	 * 設置類型為內存緩存——用於取內存緩存大小
	 */
	public static final int MEMORYSIZE=1;
	
	//設置硬盤緩存的最大值,單位為M
	private static int maxSizeForDiskLruCache=0;
	//設置內存緩存的最大值,單位為M
	private static int maxMemoryForLruCache=0;
	//設置自定義的硬盤緩存文件夾名稱
	private static String dirNameForDiskLruCache="";
	//記錄硬盤緩存與內存緩存起效標志
	private static int model=0;
	//硬盤緩存管理類
	private static DiskLruCacheManager diskLruCacheManager;
	//內存緩存管理類
	private static LruCacheManager lruCacheManager;
	private static Context ct;
	/**
	 * 初始化緩存管理
	 * @param context 上下文
	 */
	public static void init(Context context){
		ct=context;
		init_();
	}
	//根據傳入的標志,初始化內存緩存以及硬盤緩存,默認開啟是同時使用
	private static void init_(){
		switch (model) {
		case ALL_ALLOW:
			initDiskLruCacheManager();
			initLruCacheManager();
			break;
		case ONLY_LRU:
			initLruCacheManager();
			break;
		case ONLY_DISKLRU:
			initDiskLruCacheManager();
			break;
		default:
			break;
		}
	}
	//初始化內存緩存管理
	private static void initLruCacheManager(){
		if(maxMemoryForLruCache>0){
			lruCacheManager=new LruCacheManager(maxMemoryForLruCache);
		}else {
			lruCacheManager=new LruCacheManager();
		}
	}
	//初始化硬盤緩存管理
	private static void initDiskLruCacheManager(){
		if(maxSizeForDiskLruCache>0&&!TextUtils.isEmpty(dirNameForDiskLruCache)){
			 diskLruCacheManager=new DiskLruCacheManager(ct,dirNameForDiskLruCache,maxSizeForDiskLruCache*1024*1024);
		}else if(maxSizeForDiskLruCache>0){
			diskLruCacheManager=new DiskLruCacheManager(ct, maxSizeForDiskLruCache*1024*1024);
		}else if(!TextUtils.isEmpty(dirNameForDiskLruCache)){
			diskLruCacheManager=new DiskLruCacheManager(ct, dirNameForDiskLruCache);
		}else {
			diskLruCacheManager=new DiskLruCacheManager(ct);
		}
	}
	/**
	 * 設置硬盤緩存的最大值,單位為兆(M).
	 * @param maxSizeForDisk 硬盤緩存最大值,單位為兆(M)
	 */
	public static void setMaxSize(int maxSizeForDisk){
		maxSizeForDiskLruCache=maxSizeForDisk;
	}
	/**
	 * 設置內存緩存的最大值,單位為兆(M).
	 * @param maxMemory 內存緩存最大值,單位為兆(M)
	 */
	public static void setMaxMemory(int maxMemory){
		maxMemoryForLruCache=maxMemory;
	}
	/**
	 * 設置硬盤緩存自定義的文件名
	 * @param dirName 自定義文件名
	 */
	public static void setDirName(String dirName){
		dirNameForDiskLruCache=dirName;
	}
	/**
	 * 索引key對應的bitmap寫入緩存
	 * @param key 緩存索引
	 * @param bitmap bitmap格式數據
	 */
	public static void put(String key,Bitmap bitmap){
		switch (model) {
		case ALL_ALLOW:
			if(lruCacheManager!=null&&diskLruCacheManager!=null){
				//設置硬盤緩存成功後,再設置內存緩存
				if(diskLruCacheManager.putDiskCache(key,bitmap)){
					lruCacheManager.putCache(key, bitmap);
				}
			}
			break;
		case ONLY_LRU:
			if(lruCacheManager!=null){
				lruCacheManager.putCache(key, bitmap);
			}
			break;
		case ONLY_DISKLRU:
			if(diskLruCacheManager!=null){
				diskLruCacheManager.putDiskCache(key,bitmap);
			}
			break;
		default:
			break;
		}
	}
	
	/**
	 * 獲取索引key對應的緩存內容
	 * @param key 緩存索引key
	 * @return  key索引對應的Bitmap數據
	 */
	public static Bitmap get(String key){
		Bitmap bitmap=null;
		switch (model) {
		case ALL_ALLOW:
			if(lruCacheManager!=null&&diskLruCacheManager!=null){
				 bitmap=lruCacheManager.getCache(key);
				if(bitmap==null){
					//如果硬盤緩存內容存在,內存緩存不存在。則在獲取硬盤緩存後,將內容寫入內存緩存
					bitmap=diskLruCacheManager.getDiskCache(key);
					lruCacheManager.putCache(key, bitmap);
				}
			}
			break;
		case ONLY_LRU:
			if(lruCacheManager!=null){
				 bitmap=lruCacheManager.getCache(key);
			}
			break;
		case ONLY_DISKLRU:
			if(diskLruCacheManager!=null){
				 bitmap=diskLruCacheManager.getDiskCache(key);
			}
			break;

		default:
			break;
		}
		return bitmap;
	}
	/**
	 * 刪除所有緩存
	 */
	public static void delete(){
		switch (model) {
		case ALL_ALLOW:
			if(lruCacheManager!=null&&diskLruCacheManager!=null){
				lruCacheManager.deleteCache();
				diskLruCacheManager.deleteDiskCache();
			}
			break;
		case ONLY_LRU:
			if(lruCacheManager!=null){
				lruCacheManager.deleteCache();
			}
			break;
		case ONLY_DISKLRU:
			if(diskLruCacheManager!=null){
				diskLruCacheManager.deleteDiskCache();
			}
			break;

		default:
			break;
		}
	}
	
	/**
	 * 移除一條索引key對應的緩存
	 * @param key 索引
	 */
	public  static void remove(String key){
		switch (model) {
		case ALL_ALLOW:
			if(lruCacheManager!=null&&diskLruCacheManager!=null){
				lruCacheManager.removeCache(key);
				diskLruCacheManager.removeDiskCache(key);
			}
			break;
		case ONLY_LRU:
			if(lruCacheManager!=null){
				lruCacheManager.removeCache(key);
			}
			break;
		case ONLY_DISKLRU:
			if(diskLruCacheManager!=null){
				diskLruCacheManager.removeDiskCache(key);
			}
			break;

		default:
			break;
		}
	}
	/**
	 * 緩存數據同步
	 */
	public static void flush(){
		switch (model) {
		case ALL_ALLOW:
			if(lruCacheManager!=null&&diskLruCacheManager!=null){
				diskLruCacheManager.fluchCache();
			}
			break;
		case ONLY_LRU:
			break;
		case ONLY_DISKLRU:
			if(diskLruCacheManager!=null){
				diskLruCacheManager.fluchCache();
			}
			break;
		default:
			break;
		}
	}
	/**
	 * 設置緩存模式
	 * @param modelSet ONLY_LRU、ONLY_DISK、ALL_ALLOW
	 */
	public static void setCacheModel(int modelSet){
		model=modelSet;
	}
    /**
     * 刪除特定文件名的緩存文件
     * @param dirName 文件名
     */
	public static void deleteFile(String dirName){
		if(diskLruCacheManager!=null){
			diskLruCacheManager.deleteFile(ct, dirName);
		}
	}
	/**
	 * 獲取緩存大小——內存緩存+硬盤緩存
	 * @return
	 */
	public static int size(){
		int size=0;
		if(diskLruCacheManager!=null){
			size+=diskLruCacheManager.size();
		}
		if(lruCacheManager!=null){
			size+=lruCacheManager.size();
		}
		return size;
	}
	/**
	 * 獲取緩存大小
	 * @param type 硬盤緩存類型:DISKSIZE、內存緩存類型:MEMORYSIZE
	 * @return  對應類型的緩存大小
	 */
	public static int size(int type){
		int size=0;
		switch (type) {
		case DISKSIZE:
			if(diskLruCacheManager!=null){
				size+=diskLruCacheManager.size();
			}
			break;
		case MEMORYSIZE:
			if(lruCacheManager!=null){
				size+=lruCacheManager.size();
			}
			break;

		default:
			break;
		}
		return size;
	}
	/**
	 * 關閉緩存
	 */
	public static void close(){
		if(diskLruCacheManager!=null){
			diskLruCacheManager.close();
		}
	}
}

各方法在代碼中都有詳細注釋。

 

簡單的說,在使用時,如果使用默認的設置(默認情況下,內存緩存與硬盤緩存同時開啟),只需要以下幾句簡單代碼即可實現:

你首先需要初始化:CacheManager.init(Context context);

當你需要設置緩存的時候:CacheManager.put(String key,Bitmap bitmap);

當你需要獲取緩存的時候:CacheManager.get(String key);

最後:你可以在這個基礎上,添加一些其他你需要的方法,如果緩存文本、字符串等。

四、源碼

github上eclipse版本:https://github.com/yangzhaomuma/CacheManager

  1. 上一頁:
  2. 下一頁:
熱門文章
閱讀排行版
Copyright © Android教程網 All Rights Reserved