Android Content Provider 详解

核心提示：}@Overridepublic boolean onCreate() {dbHelper = new DatabaseHelper(getContext());return (dbHelper == null) ? false : true;}@Overridepublic Cursor query(Uri uri,

}

@Override

public boolean onCreate() {

dbHelper = new DatabaseHelper(getContext());

return (dbHelper == null) ? false : true;

}

@Override

public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {

SQLiteQueryBuilder qb = new SQLiteQueryBuilder();

SQLiteDatabase db = dbHelper.getReadableDatabase();

qb.setTables(TABLE_NAME);

Cursor c = qb.query(db, projection, selection, null, null, null, sortOrder);

c.setNotificationUri(getContext().getContentResolver(), uri);

return c;

}

@Override

public int update(Uri uri, ContentValues contentvalues, String s, String[] as) {

return 0;

}

}

一个名为MyContentProvider的Content Provider创建完成了，它用于从Sqlite数据库中添加和读取记录。

Content Provider的入口需要在AndroidManifest.xml中配置:

< provider android:name=”MyContentProvider” android:authorities=”com.wissen.MyContentProvider” / >

之后，让我们来使用这个定义好的Content Provider:

package com.wissen.testApp;

public class MyContentDemo extends Activity {

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

insertRecord(”MyUser”);

displayRecords();

}

private void insertRecord(String userName) {

ContentValues values = new ContentValues();

values.put(MyUsers.User.USER_NAME, userName);

getContentResolver().insert(MyUsers.User.CONTENT_URI, values);

}

private void displayRecords() {

String columns[] = new String[] { MyUsers.User._ID, MyUsers.User.USER_NAME };

Uri myUri = MyUsers.User.CONTENT_URI;

Cursor cur = managedQuery(myUri, columns,null, null, null );