Android教程網
設為首頁|加入收藏
  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開發教程之ContentProvider數據存儲

Android開發教程之ContentProvider數據存儲

編輯：關於Android編程

一、ContentProvider保存數據介紹

一個程序可以通過實現一個ContentProvider的抽象接口將自己的數據完全暴露出去，而且ContentProvider是以類似數據庫中表的方式將數據暴露的。那麼外界獲取其提供的數據，也就應該與從數據庫中獲取數據的操作基本一樣，只不過是采用URL來表示外界需要訪問的“數據庫”。

ContentProvider提供了一種多應用間數據共享的方式。

ContentProvider是個實現了一組用於提供其他應用程序存取數據的標准方法的類。應用程序可以在ContentProvider中執行如下操作：查詢數據、修改數據、添加數據、刪除數據。

標准的ContentProvider：Android提供了一些已經在系統中實現的標准ContentProvider，比如聯系人信息，圖片庫等等，可以用這些ContentProvider來訪問設備上存儲的聯系人信息、圖片等等。

在ContentProvider中使用的查詢字符串有別於標准的SQL查詢，很多諸如select、add、delete、modify等操作都使用一種特殊的URL進行，這種URL由3部分組成，“content://”，代表數據的路徑和一個可選的表示數據的ID。

content://media/internal/images 這個URL將返回設備上存儲的所有圖片

content://contacts/people/ 這個URL將返回設備上的所有聯系人信息

content://contacts/people/45 這個URL返回單個結果（聯系人信息中ID為45的聯系人記錄）

 如果想要存儲字節型數據，比如位圖文件等，那保存該數據的數據列其實是一個表示實際保存保存文件的URL字符串，客戶端通過它來讀取對應的文件數據，處理這種數據類型的ContentProvider需要實現一個名為_data的字段，_data字段列出了該文件在Android文件系統上的精確路徑。這個字段不僅是供客戶端使用，而且也可以供ContentResolver使用。客戶端可以調用ContentResolver.openOutputStream()方法來處理該URL指向的文件資源，如果是ContentResolver本身的話，由於其持有的權限比客戶端要高，所以它能直接訪問該數據文件。

二、使用方法

大多數ContentProvider使用Android文件系統或者SQLite數據庫來保持數據，但是也可以以任何方式來存儲。本例用SQLite數據庫來保持數據。

1.創建一個接口，定義了一個名為CONTENT_URL，並且是public static final的Uri類型的類變量，必須為其指定一個唯一的字符串值，最好的方案是類的全稱，和數據列的名稱。

public interface IProivderMetaData {
  public static final String AUTHORITY = "com.zhangmiao.datastoragedemo";
  public static final String DB_NAME = "book.db";
  public static final int VERSION = 1;
  public interface BookTableMetaData extends BaseColumns {
    public static final String TABLE_NAME = "book";
    public static final Uri CONTENT_URI = Uri.parse("content://"
            + AUTHORITY + "/" + TABLE_NAME);
    public static final String BOOK_ID = "_id";
    public static final String BOOK_NAME = "name";
    public static final String BOOK_PUBLISHER = "publisher";
    public static final String SORT_ORDER = "_id desc";
    public static final String CONTENT_LIST = "vnd.android.cursor.dir/vnd.bookprovider.book";
    public static final String CONTENT_ITEM = "vnd.android.cursor.item/vnd.bookprovider.book";
  }
}

2.實現SQLiteOpenHelper

public class ContentProviderDBHelper extends SQLiteOpenHelper implements IProivderMetaData {
  private static final String TAG = "ContentProviderDBHelper";
  public ContentProviderDBHelper(Context context) {
    super(context, DB_NAME, null, VERSION);
  }
  @Override
  public void onCreate(SQLiteDatabase db) {
    ...
  }
  @Override
  public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    ...
  }
}

3.創建一個繼承了ContentProvider父類的類

public class ContentProviderDBHelper extends SQLiteOpenHelper implements IProivderMetaData {
  public ContentProviderDBHelper(Context context) {
    super(context, DB_NAME, null, VERSION);
  }
  @Override
  public void onCreate(SQLiteDatabase db) {
    ...
  }
  @Override
  public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    ...
  }
}

4.在AndroidManifest.xml中使用標簽來設置調用ContentProvider。

<provider
   android:authorities="com.zhangmiao.datastoragedemo"
   android:name=".BookContentProvider"/>

5.增加數據

mContentResolver = getContentResolver();
String[] bookNames = new String[]{"Chinese", "Math", "English", "Sports"};
String[] bookPublishers = new String[]{"XinHua", "GongXin", "DianZi", "YouDian"};
for (int i = 0; i < bookNames.length; i++) {
  ContentValues values = new ContentValues();
  values.put(IProivderMetaData.BookTableMetaData.BOOK_NAME, bookNames[i]);
  values.put(IProivderMetaData.BookTableMetaData.BOOK_PUBLISHER, bookPublishers[i]);
  mContentResolver.insert(IProivderMetaData.BookTableMetaData.CONTENT_URI, values);
}

6.刪除數據

String bookId = "1";
if (!"".equals(bookId)) {
   ContentValues values1 = new ContentValues();
   values1.put(IProivderMetaData.BookTableMetaData.BOOK_ID,bookId);
   mContentResolver.delete(Uri.withAppendedPath(
                  IProivderMetaData.BookTableMetaData.CONTENT_URI,
                  bookId), 
　　　　　　　　　　      "_id = ?",
              new String[]{bookId}
   );
} else {
  mContentResolver.delete(
       IProivderMetaData.BookTableMetaData.CONTENT_URI,
       null,
       null
  );
}

7.查詢數據

Cursor cursor = mContentResolver.query(IProivderMetaData.BookTableMetaData.CONTENT_URI,
            null, null, null, null);
String text = "";
if (cursor != null) {
  while (cursor.moveToNext()) {
    String bookIdText =
cursor.getString(cursor.getColumnIndex(IProivderMetaData.BookTableMetaData.BOOK_ID));
    String bookNameText =
cursor.getString(cursor.getColumnIndex(IProivderMetaData.BookTableMetaData.BOOK_NAME));
    String bookPublisherText =
cursor.getString(cursor.getColumnIndex(IProivderMetaData.BookTableMetaData.BOOK_PUBLISHER));
    text += "id = " + bookIdText + ",name = " + bookNameText + 
          ",publisher = " + bookPublisherText + "\n";
  }
  cursor.close();
  mTableInfo.setText(text);
}

8.更新數據

String bookId1 = "2";
String bookName = "Art";
String bookPublisher = "TieDao";
ContentValues values2 = new ContentValues();
values2.put(IProivderMetaData.BookTableMetaData.BOOK_NAME,bookName);
values2.put(IProivderMetaData.BookTableMetaData.BOOK_PUBLISHER,bookPublisher);
if ("".equals(bookId1)) {
   mContentResolver.update(IProivderMetaData.BookTableMetaData.CONTENT_URI,
              values2, null, null);
} else {
   mContentResolver.update(Uri.withAppendedPath(IProivderMetaData.BookTableMetaData.CONTENT_URI, bookId1),
              values2, "_id = ? ", new String[]{bookId1}
   );
}

三、小案例

1.添加strings.xml文件

  <string name="content_provider">ContentProvider</string>
  <string name="add_data">增加數據</string>
  <string name="delete_data">刪除數據</string>
  <string name="update_data">更改數據</string>
  <string name="query_data">查詢數據</string>

2.修改activity_main.xml文件

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:tools="http://schemas.android.com/tools"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:fitsSystemWindows="true"
  tools:context="com.zhangmiao.datastoragedemo.MainActivity">
  <LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">
    <TextView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_gravity="center_horizontal"
      android:text="@string/content_provider" />
    <LinearLayout
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:layout_marginBottom="@dimen/fab_margin"
      android:layout_marginTop="@dimen/fab_margin"
      android:orientation="horizontal">
      <Button
        android:id="@+id/provider_add"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="@string/add_data" />
      <Button
        android:id="@+id/provider_delete"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="@string/delete_data" />
      <Button
        android:id="@+id/provider_update"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="@string/update_data" />
      <Button
        android:id="@+id/provider_query"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="@string/query_data" />
    </LinearLayout>
    <TextView
      android:id="@+id/table_info"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:text="@string/app_name" />
  </LinearLayout>
</android.support.design.widget.CoordinatorLayout>

3.添加IProviderMetaData接口

package com.zhangmiao.datastoragedemo;
import android.net.Uri;
import android.provider.BaseColumns;
/**
 * Created by zhangmiao on 2016/12/20.
 */
public interface IProviderMetaData {
  public static final String AUTHORITY = "com.zhangmiao.datastoragedemo";
  public static final String DB_NAME = "book.db";
  public static final int VERSION = 1;
  public interface BookTableMetaData extends BaseColumns {
    public static final String TABLE_NAME = "book";
    public static final Uri CONTENT_URI = Uri.parse("content://"
            + AUTHORITY + "/" + TABLE_NAME);
    public static final String BOOK_ID = "_id";
    public static final String BOOK_NAME = "name";
    public static final String BOOK_PUBLISHER = "publisher";
    public static final String SORT_ORDER = "_id desc";
    public static final String CONTENT_LIST = "vnd.android.cursor.dir/vnd.bookprovider.book";
    public static final String CONTENT_ITEM = "vnd.android.cursor.item/vnd.bookprovider.book";
  }
}

4.添加ContentProviderDBHelper類

package com.zhangmiao.datastoragedemo;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
/**
 * Created by zhangmiao on 2016/12/20.
 */
public class ContentProviderDBHelper extends SQLiteOpenHelper implements IProviderMetaData {
  private static final String TAG = "ContentProviderDBHelper";
  public ContentProviderDBHelper(Context context) {
    super(context, DB_NAME, null, VERSION);
  }
  @Override
  public void onCreate(SQLiteDatabase db) {
    String TABLESQL = "CREATE TABLE IF NOT EXISTS "
        + BookTableMetaData.TABLE_NAME + " ("
        + BookTableMetaData.BOOK_ID + " INTEGER PRIMARY KEY AUTOINCREMENT,"
        + BookTableMetaData.BOOK_NAME + " VARCHAR,"
        + BookTableMetaData.BOOK_PUBLISHER + " VARCHAR)";
    db.execSQL(TABLESQL);
  }
  @Override
  public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    Log.w(TAG, "Upgrading database from version " + oldVersion + "to"
        + newVersion + ", which will destroy all old data");
    db.execSQL("DROP TABLE IF EXISTS " + DB_NAME);
    onCreate(db);
  }
}

5.添加BookContentProvider類

package com.zhangmiao.datastoragedemo;
import android.content.ContentProvider;
import android.content.ContentUris;
import android.content.ContentValues;
import android.content.UriMatcher;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;
import android.support.annotation.Nullable;
import android.util.Log;
/**
 * Created by zhangmiao on 2016/12/21.
 */
public class BookContentProvider extends ContentProvider {
  private static final String TAG = "BookContentProvider";
  private static UriMatcher uriMatcher = null;
  private static final int BOOKS = 1;
  private static final int BOOK = 2;
  private ContentProviderDBHelper dbHelper;
  private SQLiteDatabase db;
  static {
    uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
    uriMatcher.addURI(IProviderMetaData.AUTHORITY,
        IProviderMetaData.BookTableMetaData.TABLE_NAME, BOOKS);
    uriMatcher.addURI(IProviderMetaData.AUTHORITY,
        IProviderMetaData.BookTableMetaData.TABLE_NAME + "/#",
        BOOK);
  }
  @Override
  public boolean onCreate() {
    dbHelper = new ContentProviderDBHelper(getContext());
    return (dbHelper == null) ? false : true;
  }
  @Nullable
  @Override
  public String getType(Uri uri) {
    switch (uriMatcher.match(uri)) {
      case BOOKS:
        return IProviderMetaData.BookTableMetaData.CONTENT_LIST;
      case BOOK:
        return IProviderMetaData.BookTableMetaData.CONTENT_ITEM;
      default:
        throw new IllegalArgumentException("This is a unKnow Uri"
            + uri.toString());
    }
  }
  @Nullable
  @Override
  public Uri insert(Uri uri, ContentValues values) {
    switch (uriMatcher.match(uri)) {
      case BOOKS:
        db = dbHelper.getWritableDatabase();
        long rowId = db.insert(
            IProviderMetaData.BookTableMetaData.TABLE_NAME,
            IProviderMetaData.BookTableMetaData.BOOK_ID,
            values);
        Uri insertUri = Uri.withAppendedPath(uri, "/" + rowId);
        Log.i(TAG, "insertUri:" + insertUri.toString());
        getContext().getContentResolver().notifyChange(uri, null);
        return insertUri;
      case BOOK:
      default:
        throw new IllegalArgumentException("This is a unKnow Uri"
            + uri.toString());
    }
  }
  @Nullable
  @Override
  public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
    db = dbHelper.getReadableDatabase();
    switch (uriMatcher.match(uri)) {
      case BOOKS:
        return db.query(IProviderMetaData.BookTableMetaData.TABLE_NAME,
            projection, selection, selectionArgs, null, null,
            sortOrder);
      case BOOK:
        long id = ContentUris.parseId(uri);
        String where = "_id=" + id;
        if (selection != null && !"".equals(selection)) {
          where = selection + " and " + where;
        }
        return db.query(IProviderMetaData.BookTableMetaData.TABLE_NAME,
            projection, where, selectionArgs, null, null, sortOrder);
      default:
        throw new IllegalArgumentException("This is a unKnow Uri"
            + uri.toString());
    }
  }
  @Override
  public int delete(Uri uri, String selection, String[] selectionArgs) {
    db = dbHelper.getWritableDatabase();
    switch (uriMatcher.match(uri)) {
      case BOOKS:
        return db.delete(IProviderMetaData.BookTableMetaData.TABLE_NAME,
            selection, selectionArgs);
      case BOOK:
        long id = ContentUris.parseId(uri);
        String where = "_id=" + id;
        if (selection != null && !"".equals(selection)) {
          where = selection + " and " + where;
        }
        return db.delete(IProviderMetaData.BookTableMetaData.TABLE_NAME,
            selection, selectionArgs);
      default:
        throw new IllegalArgumentException("This is a unKnow Uri"
            + uri.toString());
    }
  }
  @Override
  public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
    db = dbHelper.getWritableDatabase();
    switch (uriMatcher.match(uri)) {
      case BOOKS:
        return db.update(IProviderMetaData.BookTableMetaData.TABLE_NAME,
            values, null, null);
      case BOOK:
        long id = ContentUris.parseId(uri);
        String where = "_id=" + id;
        if (selection != null && !"".equals(selection)) {
          where = selection + " and " + where;
        }
        return db.update(IProviderMetaData.BookTableMetaData.TABLE_NAME,
            values, selection, selectionArgs);
      default:
        throw new IllegalArgumentException("This is a unKnow Uri"
            + uri.toString());
    }
  }
}

6.修改AndroidManifest.xml文件

<provider
      android:authorities="com.zhangmiao.datastoragedemo"
      android:name=".BookContentProvider"/>

7.修改MainActivity

package com.zhangmiao.datastoragedemo;
import android.content.ContentResolver;
import android.content.ContentValues;
import android.database.Cursor;
import android.net.*;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;import java.util.ArrayList;
import java.util.List;
public class MainActivity extends AppCompatActivity implements View.OnClickListener {private ContentResolver mContentResolver;
  private BookContentProvider mBookContentProvider;private TextView mTableInfo;
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    Log.v("MainActivity", "onCreate");
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Button cpAdd = (Button) findViewById(R.id.provider_add);
    Button cpDelete = (Button) findViewById(R.id.provider_delete);
    Button cpUpdate = (Button) findViewById(R.id.provider_update);
    Button cpQuery = (Button) findViewById(R.id.provider_query);
    mTableInfo = (TextView) findViewById(R.id.table_info);
    cpAdd.setOnClickListener(this);
    cpDelete.setOnClickListener(this);
    cpQuery.setOnClickListener(this);
    cpUpdate.setOnClickListener(this);
  }
  @Override
  public void onClick(View v) {
    switch (v.getId()) {case R.id.provider_add:
        mContentResolver = getContentResolver();
        String[] bookNames = new String[]{"Chinese", "Math", "English", "Sports"};
        String[] bookPublishers = new String[]{"XinHua", "GongXin", "DianZi", "YouDian"};
        for (int i = 0; i < bookNames.length; i++) {
          ContentValues values = new ContentValues();
          values.put(IProviderMetaData.BookTableMetaData.BOOK_NAME, bookNames[i]);
          values.put(IProviderMetaData.BookTableMetaData.BOOK_PUBLISHER, bookPublishers[i]);
          mContentResolver.insert(IProviderMetaData.BookTableMetaData.CONTENT_URI, values);
        }
        break;
      case R.id.provider_delete:
        String bookId = "1";
        if (!"".equals(bookId)) {
          ContentValues values1 = new ContentValues();
          values1.put(IProviderMetaData.BookTableMetaData.BOOK_ID,
              bookId);
          mContentResolver.delete(
              Uri.withAppendedPath(
                  IProviderMetaData.BookTableMetaData.CONTENT_URI,
                  bookId
              ), "_id = ?",
              new String[]{bookId}
          );
        } else {
          mContentResolver.delete(
              IProviderMetaData.BookTableMetaData.CONTENT_URI,
              null,
              null
          );
        }
        break;
      case R.id.provider_query:
        Cursor cursor = mContentResolver.query(IProviderMetaData.BookTableMetaData.CONTENT_URI, null, null, null, null);
        String text = "";
        if (cursor != null) {
          while (cursor.moveToNext()) {
            String bookIdText =
                cursor.getString(cursor.getColumnIndex(IProviderMetaData.BookTableMetaData.BOOK_ID));
            String bookNameText =
                cursor.getString(cursor.getColumnIndex(IProviderMetaData.BookTableMetaData.BOOK_NAME));
            String bookPublisherText =
                cursor.getString(cursor.getColumnIndex(IProviderMetaData.BookTableMetaData.BOOK_PUBLISHER));
            text += "id = " + bookIdText + ",name = " + bookNameText + ",publisher = " + bookPublisherText + "\n";
          }
          cursor.close();
          mTableInfo.setText(text);
        }
        break;
      case R.id.provider_update:
        String bookId1 = "2";
        String bookName = "Art";
        String bookPublisher = "TieDao";
        ContentValues values2 = new ContentValues();
        values2.put(IProviderMetaData.BookTableMetaData.BOOK_NAME,
            bookName);
        values2.put(IProviderMetaData.BookTableMetaData.BOOK_PUBLISHER,
            bookPublisher);
        if ("".equals(bookId1)) {
          mContentResolver.update(
              IProviderMetaData.BookTableMetaData.CONTENT_URI,
              values2, null, null);
        } else {
          mContentResolver.update(
              Uri.withAppendedPath(
                  IProviderMetaData.BookTableMetaData.CONTENT_URI, bookId1),
              values2, "_id = ? ", new String[]{bookId1});
        }
        break;default:
        Log.v("MainActivity", "default");
        break;
    }
  }
}

  1. 上一頁:
  2. 下一頁:
關於Android編程
Android編程入門Android技術基礎Android資訊關於Android編程Android開發Android開發環境Android開發實例
相關文章
熱門文章
Android - 組件工具箱(widget tool box) Android實戰技巧之四十六：用patch更新Android Studio Android 性能優化 UI優化 Android筆記——自動顯示、隱藏布局的ListView 網絡請求庫之android-async-http Eclipse下配置Ant腳本並自動打包帶簽名的Android apk
android:數據存貯方式-SharedPreference

SharedPreference:1.是一種輕型的數據存貯方式2.本質是
android使用百度地圖SDK獲取定位信息示例

本文使用Android Studio開發。獲取定位信息相對簡單，我們只需
[Android][Memory Leak] InputMethodManager內存洩露現象及解決

[Android][Memory Leak] InputMethodMa
android源碼解析（十九）--)Dialog加載繪制流程

前面兩篇文章，我們分析了Activity的布局文件加載、繪制流程，算是對
閱讀排行版
Copyright © Android教程網 All Rights Reserved