Android的設(shè)計之中，任何耗時的操作都不能放在UI主線程之中。所以類似于網(wǎng)絡(luò)操作等等耗時的操作都需要使用異步的實現(xiàn)。而在ContentProvider之中，也有可能存在耗時的操作（當(dāng)查詢的數(shù)據(jù)量很大的時候），這個時候我們也需要使用異步的調(diào)用來完成數(shù)據(jù)的查詢。

當(dāng)使用異步的query的時候，我們就需要使用LoaderManager了。使用LoaderManager就可以在不阻塞UI主線程的情況下完成數(shù)據(jù)的加載。

（1）獲取loaderManger：activity.getLoaderManager()

（2）loaderManager的事件回調(diào)接口, LoaderManager.LoaderCallbacks<D>

下面是一個demo，從contentprovider中query數(shù)據(jù)添加到listview中，是異步執(zhí)行的。

MySQLiteOpenHeleper.java:

package com.app.loadermanager;import android.content.Context;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteDatabase.CursorFactory;import android.database.sqlite.SQLiteOpenHelper; public class MySQLiteOpenHelper extends SQLiteOpenHelper {   public static final String db_name = "test.db3";  public static final int version = 1;   public MySQLiteOpenHelper(Context context) {    super(context, db_name, null, version);  }   @Override  public void onCreate(SQLiteDatabase db) {     String create_sql = "create table tb_student(_id integer primary key autoincrement,name varchar(20),age integer)";    db.execSQL(create_sql);  }   @Override  public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {   } }

MyContentProvider.java

package com.app.loadermanager; 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; public class MyContentProvider extends ContentProvider {   private MySQLiteOpenHelper helper = null;  private static final UriMatcher matcher = new UriMatcher(      UriMatcher.NO_MATCH);  private static final int students = 1;  static {    matcher.addURI("com.app.contentprovider", "tb_student", students);  }   @Override  public int delete(Uri arg0, String arg1, String[] arg2) {    return 0;  }   @Override  public String getType(Uri arg0) {    return null;  }   @Override  public Uri insert(Uri uri, ContentValues values) {    SQLiteDatabase db = helper.getWritableDatabase();    int flag = matcher.match(uri);    switch (flag) {    case students:      long id = db.insert("tb_student", null, values);      return ContentUris.withAppendedId(uri, id);    }    return null;  }   @Override  public boolean onCreate() {    helper = new MySQLiteOpenHelper(this.getContext());    return true;  }   @Override  public Cursor query(Uri uri, String[] projection, String selection,      String[] selectionArgs, String sortOrder) {    SQLiteDatabase db = helper.getWritableDatabase();    Cursor cursor=db.query("tb_student", projection, selection, selectionArgs, null, null, null);    return cursor;  }   @Override  public int update(Uri uri, ContentValues values, String selection,      String[] selectionArgs) {    return 0;  } }