详细讲解Android中使用LoaderManager加载数据的方法

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) {
 
  }
 
}

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;
  }
 
}

package com.app.loadermanager;
 
import java.util.ArrayList;
 
import android.annotation.SuppressLint;
import android.app.Activity;
import android.app.LoaderManager;
import android.content.CursorLoader;
import android.content.Loader;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.ListView;
 
@SuppressLint("NewApi")
public class MainActivity extends Activity implements
    LoaderManager.LoaderCallbacks<Cursor> {
 
  LoaderManager manager = null;
  ListView listView = null;
 
  @SuppressLint("NewApi")
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    listView = (ListView) this.findViewById(R.id.listview);
    manager = this.getLoaderManager();
    manager.initLoader(1000, null, this);
  }
 
  @Override
  public Loader<Cursor> onCreateLoader(int id, Bundle bundle) {
    CursorLoader loader = new CursorLoader(this,
        Uri.parse("content://com.app.contentprovider"), null, null,
        null, null);
    return loader;
  }
 
  @Override
  public void onLoadFinished(Loader<Cursor> loader, Cursor cursor) {
    ArrayList<String> al = new ArrayList<String>();
    while (cursor.moveToNext()) {
      String name = cursor.getString(cursor.getColumnIndex("name"));
      al.add(name);
    }
    ArrayAdapter adapter=new ArrayAdapter(this,android.R.layout.simple_list_item_1,al);
    listView.setAdapter(adapter);
    adapter.notifyDataSetChanged();
     
  }
 
  @Override
  public void onLoaderReset(Loader<Cursor> loader) {
 
  }
}

   LoaderManagerImpl getLoaderManager(String who, boolean started, boolean create) {
     if (mAllLoaderManagers == null) {
       mAllLoaderManagers = new ArrayMap<String, LoaderManagerImpl>();
     }
     LoaderManagerImpl lm = mAllLoaderManagers.get(who);
     if (lm == null) {
       if (create) {
         lm = new LoaderManagerImpl(who, this, started);
         mAllLoaderManagers.put(who, lm);
       }
     } else {
       lm.updateActivity(this);
     }
     return lm;
   }

   public LoaderManager getLoaderManager() {
     if (mLoaderManager != null) {
       return mLoaderManager;
     }
     mCheckedForLoaderManager = true;
     mLoaderManager = getLoaderManager("(root)", mLoadersStarted, true);
     return mLoaderManager;
   }