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 Android教程網 >> Android技術 >> Android開發實例 >> 系出名門Android(9) - 數據庫支持(SQLite), 內容提供器(ContentProvider)

系出名門Android(9) - 數據庫支持(SQLite), 內容提供器(ContentProvider)

編輯:Android開發實例

 

  介紹

  在 Android 中使用 SQLite, ContentProvider

  * 數據庫支持(SQLite) - Android 開發平台提供了操作 SQLite 數據庫的相關 API

  * 內容提供器(ContentProvider) - 當數據需要在應用程序之間共享時,可以在某程序中使用 ContentProvider 定義 URI, 以使其它應用程序可以通過此 URI 訪問指定的數據

  1、SQLite 的 Demo

  DatabaseHelper.java

  代碼

package com.webabcd.SQLite;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
// 數據庫操作的 Helper 類
public class DatabaseHelper extends SQLiteOpenHelper {
    DatabaseHelper(Context context, String name, CursorFactory cursorFactory, int version) {
        super(context, name, cursorFactory, version);
    }
    @Override
    public void onCreate(SQLiteDatabase db) {
        // TODO 創建數據庫後,對數據庫的操作
    }
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // TODO 更改數據庫版本的操作
    }
    @Override
    public void onOpen(SQLiteDatabase db) {
        super.onOpen(db);
        
        // TODO 每次成功打開數據庫後首先被執行
    }
}

  Main.java

  代碼

package com.webabcd.SQLite;
import java.util.Random;
import android.app.Activity;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
public class Main extends Activity {
    private DatabaseHelper dbHelper;
    private static final String DATABASE_NAME = "db.db";
    private static final int DATABASE_VERSION = 1;
    private static final String TABLE_NAME = "employee";
    TextView txtMsg;
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        dbHelper = new DatabaseHelper(this, DATABASE_NAME, null,
                DATABASE_VERSION);
        txtMsg = (TextView) this.findViewById(R.id.txtMsg);
        Button btn1 = (Button) this.findViewById(R.id.btn1);
        btn1.setText("創建表");
        btn1.setOnClickListener(new Button.OnClickListener() {
            public void onClick(View v) {
                CreateTable();
            }
        });
        Button btn2 = (Button) this.findViewById(R.id.btn2);
        btn2.setText("插入 3 條記錄");
        btn2.setOnClickListener(new Button.OnClickListener() {
            public void onClick(View v) {
                insertItem();
            }
        });
        Button btn3 = (Button) this.findViewById(R.id.btn3);
        btn3.setText("刪除全部記錄");
        btn3.setOnClickListener(new Button.OnClickListener() {
            public void onClick(View v) {
                deleteItem();
            }
        });
        Button btn4 = (Button) this.findViewById(R.id.btn4);
        btn4.setText("更新指定數據");
        btn4.setOnClickListener(new Button.OnClickListener() {
            public void onClick(View v) {
                updateItem();
            }
        });
        Button btn5 = (Button) this.findViewById(R.id.btn5);
        btn5.setText("顯示全部數據");
        btn5.setOnClickListener(new Button.OnClickListener() {
            public void onClick(View v) {
                showItems();
            }
        });
        Button btn6 = (Button) this.findViewById(R.id.btn6);
        btn6.setText("刪除表");
        btn6.setOnClickListener(new Button.OnClickListener() {
            public void onClick(View v) {
                dropTable();
            }
        });
    }
    // 創建數據表
    private void CreateTable() {
        SQLiteDatabase db = dbHelper.getWritableDatabase();
        String sql = "CREATE TABLE IF NOT EXISTS "   TABLE_NAME
                  " (ID INTEGER PRIMARY KEY, Name VARCHAR, Age INTEGER);";
        try {
            db.execSQL(sql);
            txtMsg.append("數據表成功創建n");
        } catch (SQLException ex) {
            txtMsg.append("數據表創建錯誤n"   ex.toString()   "n");
        }
    }
    // 插入數據
    private void insertItem() {
        SQLiteDatabase db = dbHelper.getWritableDatabase();
        
        try {
            Random random = new Random();
            for (int i = 0; i < 3; i ) {
                String sql = "insert into "   TABLE_NAME
                          " (name, age) values ('name"   String.valueOf(i)
                          "', "   random.nextInt()   ")";
                // execSQL() - 執行指定的 sql
                db.execSQL(sql);
            }
            txtMsg.append("成功插入 3 條數據n");
        } catch (SQLException ex) {
            txtMsg.append("插入數據失敗n"   ex.toString()   "n");
        }
    }
    // 刪除數據
    private void deleteItem() {
        try {
            SQLiteDatabase db = dbHelper.getWritableDatabase();
            db.delete(TABLE_NAME, " id < 999999", null);
            txtMsg.append("成功刪除數據n");
        } catch (SQLException e) {
            txtMsg.append("刪除數據失敗n");
        }
    }
    // 更新數據
    private void updateItem() {
        SQLiteDatabase db = dbHelper.getWritableDatabase();
        try {
            ContentValues values = new ContentValues();
            values.put("name", "批量更新後的名字");
            db.update(TABLE_NAME, values, "id<?", new String[] { "3" });
            txtMsg.append("成功更新數據n");
        } catch (SQLException e) {
            txtMsg.append("更新數據失敗n");
        }
    }
    // 查詢數據
    private void showItems() {
        SQLiteDatabase db = dbHelper.getReadableDatabase();
        try {
            String[] column = { "id", "name", "age" };
            Cursor cursor = db.query(TABLE_NAME, column, null, null, null,
                    null, null);
            Integer num = cursor.getCount();
            txtMsg.append("共 "   Integer.toString(num)   " 條記錄n");
            cursor.moveToFirst();
            while (cursor.getPosition() != cursor.getCount()) {
                txtMsg.append(Integer.toString(cursor.getPosition())   ","
                          String.valueOf(cursor.getString(0))   ","
                          cursor.getString(1)   ","
                          String.valueOf(cursor.getString(2))   "n");
                cursor.moveToNext();
            }
        } catch (SQLException ex) {
            txtMsg.append("讀取數據失敗n"   ex.toString()   "n");
        }
    }
    // 刪除數據表
    private void dropTable() {
        SQLiteDatabase db = dbHelper.getWritableDatabase();
        String sql = "DROP TABLE IF EXISTS "   TABLE_NAME;
        try {
            db.execSQL(sql);
            txtMsg.append("數據表刪除成功n");
        } catch (SQLException ex) {
            txtMsg.append("數據表刪除錯誤n"   ex.toString()   "n");
        }
    }
}

  2、ContentProvider 的 Demo

  MyUser.java

  代碼

package com.webabcd.contentprovider;
import android.net.Uri;
import android.provider.BaseColumns;
// 自定義 ContentProvider 所需的實體類
public class MyUser {
    // 必須要有 _id 字段。本例中 BaseColumn 類中已經包含了 _id 字段
    public static final class User implements BaseColumns {
        
        // 定義 CONTENT_URI
        public static final Uri CONTENT_URI = Uri.parse("content://com.webabcd.MyContentProvider");
        // 表數據列
        public static final String USER_NAME = "USER_NAME";
    }
}

  MyContentProvider.java

  代碼

package com.webabcd.contentprovider;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import org.apache.http.util.EncodingUtils;
import android.content.ContentProvider;
import android.content.ContentUris;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.MatrixCursor;
import android.net.Uri;
// 繼承 ContentProvider 以實現自定義的 ContentProvider(基於文件的信息存儲)
public class MyContentProvider extends ContentProvider {
    private File file;
    private FileOutputStream out;
    private FileInputStream in;
    // ContentProvider 的刪除數據接口
    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs) {
        // TODO Auto-generated method stub
        return 0;
    }
    @Override
    public String getType(Uri uri) {
        // TODO Auto-generated method stub
        return null;
    }
    // ContentProvider 的插入數據接口 
    @Override
    public Uri insert(Uri uri, ContentValues values) {
        try {
            out = new FileOutputStream(file);
            out.write(values.getAsString(MyUser.User.USER_NAME).getBytes());
            out.close();
            int rowId = 0;
            Uri rowUri = ContentUris.appendId(
                    MyUser.User.CONTENT_URI.buildUpon(), rowId).build();
            getContext().getContentResolver().notifyChange(rowUri, null);
            return rowUri;
        } catch (Exception e) {
            return null;
        }
    }
    // 創建用於保存信息的文件
    @Override
    public boolean onCreate() {
        try {
            // 每個包中應用程序的私有目錄為:/data/data/包名/
            // SD 卡目錄為:/sdcard
            file = new File("/data/data/com.webabcd.contentprovider/",
                    "demo.txt");
            if (!file.exists())
                file.createNewFile();
            return true;
        } catch (Exception ex) {
            return false;
        }
    }
    // ContentProvider 的查詢數據接口
    @Override
    public Cursor query(Uri uri, String[] projection, String selection,
            String[] selectionArgs, String sortOrder) {
        
        String content;
        try {
            in = new FileInputStream(file);
            int length = (int) file.length();
            byte[] buffer = new byte[length];
            in.read(buffer, 0, length);
            content = EncodingUtils.getString(buffer, "UTF-8");
            in.close();
            String[] columns = new String[] { MyUser.User._ID, MyUser.User.USER_NAME };
            MatrixCursor cur = new MatrixCursor(columns);
            String[] values = new String[] { "0", content };
            cur.moveToFirst();
            cur.addRow(values);
            return cur;
        } catch (Exception e) {
            return null;
        }
    }
    // ContentProvider 的更新數據接口
    @Override
    public int update(Uri uri, ContentValues values, String selection,
            String[] selectionArgs) {
        // TODO Auto-generated method stub
        return 0;
    }
}

  Main.java

  代碼

package com.webabcd.contentprovider;
import java.util.Random;
import android.app.Activity;
import android.content.ContentUris;
import android.content.ContentValues;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.provider.Contacts;
import android.provider.Contacts.People;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
/*
 * 幾個常用的系統內置的 ContentProvider 如下: 
 * content://media/internal/images  這個URI將返回設備上存儲的所有圖片
 * content://contacts/people/ 這個URI將返回設備上的所有聯系人信息
 * content://contacts/people/45 這個URI返回單個結果(聯系人信息中ID為45的聯系人記錄)
 */
public class Main extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        Button btn1 = (Button) this.findViewById(R.id.btn1);
        btn1.setText("新增聯系人記錄");
        btn1.setOnClickListener(new Button.OnClickListener() {
            public void onClick(View v) {
                Random random = new Random();
                insertRecords("name"   String.valueOf(random.nextInt()), String
                        .valueOf(random.nextInt()));
            }
        });
        Button btn2 = (Button) this.findViewById(R.id.btn2);
        btn2.setText("查看聯系人記錄");
        btn2.setOnClickListener(new Button.OnClickListener() {
            public void onClick(View v) {
                displayRecords();
            }
        });
        Button btn3 = (Button) this.findViewById(R.id.btn3);
        btn3.setText("清除聯系人記錄");
        btn3.setOnClickListener(new Button.OnClickListener() {
            public void onClick(View v) {
                deleteRecords();
            }
        });
        Button btn4 = (Button) this.findViewById(R.id.btn4);
        btn4.setText("更新聯系人記錄");
        btn4.setOnClickListener(new Button.OnClickListener() {
            public void onClick(View v) {
                // 此處只是演示,id 來自 People._ID ,可參見 displayRecords() 是如何獲取 id 的
                int id = 0;
                updateRecord(id, "修改後的name");
            }
        });
        Button btn5 = (Button) this.findViewById(R.id.btn5);
        btn5.setText("新增記錄到 MyContentProvider");
        btn5.setOnClickListener(new Button.OnClickListener() {
            public void onClick(View v) {
                insertRecord2MyContentProvider("webabcd");
            }
        });
        Button btn6 = (Button) this.findViewById(R.id.btn6);
        btn6.setText("獲取記錄從 MyContentProvider");
        btn6.setOnClickListener(new Button.OnClickListener() {
            public void onClick(View v) {
                displayRecord2MyContentProvider();
            }
        });
    }
    // 調用 ContentProvider 的插入接口
    private void insertRecords(String name, String phoneNum) {
        ContentValues values = new ContentValues();
        values.put(People.NAME, name);
        Uri uri = getContentResolver().insert(People.CONTENT_URI, values);
        Log.d("MyDebug", uri.toString());
        Uri numberUri = Uri.withAppendedPath(uri,
                People.Phones.CONTENT_DIRECTORY);
        Log.d("MyDebug", numberUri.toString());
        values.clear();
        values.put(Contacts.Phones.TYPE, People.Phones.TYPE_MOBILE);
        values.put(People.NUMBER, phoneNum);
        getContentResolver().insert(numberUri, values);
    }
    // 調用 ContentProvider 的查詢接口
    private void displayRecords() {
        String[] columns = new String[] { People._ID, People.NAME,
                People.NUMBER };
        Uri contacts = People.CONTENT_URI;
        Log.d("MyDebug", contacts.toString());
        Cursor cur = managedQuery(contacts, columns, // 要返回的數據字段
                null, // WHERE子句
                null, // WHERE 子句的參數
                null // Order-by子句
        );
        if (cur.moveToFirst()) {
            String id = null;
            String name = null;
            String phoneNo = null;
            while (cur.getPosition() != cur.getCount()) {
                id = cur.getString(cur.getColumnIndex(People._ID));
                name = cur.getString(cur.getColumnIndex(People.NAME));
                phoneNo = cur.getString(cur.getColumnIndex(People.NUMBER));
                Toast.makeText(this, id   " / "   name   " / "   phoneNo,
                        Toast.LENGTH_SHORT).show();
                cur.moveToNext();
            }
        }
    }
    // 調用 ContentProvider 的刪除接口
    private void deleteRecords() {
        Uri uri = People.CONTENT_URI;
        Log.d("MyDebug", uri.toString());
        getContentResolver().delete(uri, null, null);
        // getContentResolver().delete(uri, "NAME="   "'name'", null);
    }
    // 調用 ContentProvider 的更新接口
    private void updateRecord(int recordNo, String name) {
        Uri uri = ContentUris.withAppendedId(People.CONTENT_URI, recordNo);
        Log.d("MyDebug", uri.toString());
        ContentValues values = new ContentValues();
        values.put(People.NAME, name);
        getContentResolver().update(uri, values, null, null);
    }
    
    // 調用自定義 ContentProvider 的插入接口
    private void insertRecord2MyContentProvider(String name) {
        ContentValues values = new ContentValues();
        values.put(MyUser.User.USER_NAME, name);
        getContentResolver().insert(MyUser.User.CONTENT_URI, values);
    }
    // 調用自定義 ContentProvider 的查詢接口
    private void displayRecord2MyContentProvider() {
        String[] columns = new String[] { MyUser.User.USER_NAME };
        Uri uri = MyUser.User.CONTENT_URI;
        Cursor cur = managedQuery(uri, columns, null, null, null);
        while (cur.getPosition() != cur.getCount()) {
            String id = cur.getString(cur.getColumnIndex(People._ID));
            String name = cur.getString(cur.getColumnIndex(MyUser.User.USER_NAME));
            Toast.makeText(this,
                    id   " / "   name,
                    Toast.LENGTH_SHORT).show();
            cur.moveToNext();
        }
    }
}

  AndroidManifest.xml

  代碼

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="com.webabcd.contentprovider"
      android:versionCode="1"
      android:versionName="1.0">
    <application android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name=".Main"
                  android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        
        <!--
            配置一個自定義的 ContentProvider"
        -->
        <provider android:name="MyContentProvider" android:authorities="com.webabcd.MyContentProvider" />
    </application>
    <uses-permission android:name="android.permission.WRITE_CONTACTS"></uses-permission>
    <uses-permission android:name="android.permission.READ_CONTACTS"></uses-permission>
    <uses-sdk android:minSdkVersion="3" />
</manifest> 

  [源碼下載]

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