我有一个ListFragment其名单应diplay设备并使用相关的艺术家的专辑MediaStore 。 每一行都有因此，两个TextViews 。 我使用LoaderManager和CursorLoader填充列表起来，用一个自定义的CursorAdapter为了绑定TextViews该行的数据。
ListFragment代码：
public class AlbumsFragment extends ListFragment implements LoaderManager.LoaderCallbacks<Cursor> {
AlbumsAdapter mAdapter;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View myFragmentView = inflater.inflate(R.layout.albums_fragment_layout, container, false);
return myFragmentView;
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
setListAdapter(mAdapter);
getLoaderManager().initLoader(0, null, this);
}
static final String[] ALBUM_SUMMARY_PROJECTION = { MediaStore.Audio.Albums.ALBUM, MediaStore.Audio.Albums.ARTIST};
public Loader<Cursor> onCreateLoader(int id, Bundle args) {
String select = null;
return new CursorLoader(getActivity(), MediaStore.Audio.Albums.EXTERNAL_CONTENT_URI,ALBUM_SUMMARY_PROJECTION, select, null, null);
}
public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
mAdapter.swapCursor(data);
}
public void onLoaderReset(Loader<Cursor> loader) {
mAdapter.swapCursor(null);
}
}
AlbumsAdapter（自定义的CursorAdapter）代码：
public class AlbumsAdapter extends CursorAdapter {
private final LayoutInflater mInflater;
public AlbumsAdapter(Context context, Cursor c) {
super(context, c);
mInflater=LayoutInflater.from(context);
}
@Override
public void bindView(View view, Context context, Cursor cursor) {
TextView albumTitle =(TextView)view.findViewById(R.id.albumTextView);
albumTitle.setText(cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Albums.ALBUM)));
TextView artistName=(TextView)view.findViewById(R.id.artistTextView);
artistName.setText(cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Albums.ARTIST)));
}
@Override
public View newView(Context context, Cursor cursor, ViewGroup parent) {
final View view=mInflater.inflate(R.layout.albums_row,parent,false);
return view;
}
目前，当我显示此ListFragment，我有一个显示java.lang.NullPointerException，这里是logcat的：
06-14 09:39:23.109: W/dalvikvm(8632): threadid=1: thread exiting with uncaught exception (group=0x40c2d1f8)
06-14 09:39:23.109: E/AndroidRuntime(8632): FATAL EXCEPTION: main
06-14 09:39:23.109: E/AndroidRuntime(8632): java.lang.NullPointerException
06-14 09:39:23.109: E/AndroidRuntime(8632): at com.music.pod.AlbumsFragment.onLoadFinished(AlbumsFragment.java:61)
06-14 09:39:23.109: E/AndroidRuntime(8632): at com.music.pod.AlbumsFragment.onLoadFinished(AlbumsFragment.java:1)
06-14 09:39:23.109: E/AndroidRuntime(8632): at android.app.LoaderManagerImpl$LoaderInfo.callOnLoadFinished(LoaderManager.java:438)
06-14 09:39:23.109: E/AndroidRuntime(8632): at android.app.LoaderManagerImpl$LoaderInfo.onLoadComplete(LoaderManager.java:406)
06-14 09:39:23.109: E/AndroidRuntime(8632): at android.content.Loader.deliverResult(Loader.java:125)
06-14 09:39:23.109: E/AndroidRuntime(8632): at android.content.CursorLoader.deliverResult(CursorLoader.java:88)
06-14 09:39:23.109: E/AndroidRuntime(8632): at android.content.CursorLoader.deliverResult(CursorLoader.java:42)
06-14 09:39:23.109: E/AndroidRuntime(8632): at android.content.AsyncTaskLoader.dispatchOnLoadComplete(AsyncTaskLoader.java:236)
06-14 09:39:23.109: E/AndroidRuntime(8632): at android.content.AsyncTaskLoader$LoadTask.onPostExecute(AsyncTaskLoader.java:76)
06-14 09:39:23.109: E/AndroidRuntime(8632): at android.os.AsyncTask.finish(AsyncTask.java:602)
06-14 09:39:23.109: E/AndroidRuntime(8632): at android.os.AsyncTask.access$600(AsyncTask.java:156)
06-14 09:39:23.109: E/AndroidRuntime(8632): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:615)
06-14 09:39:23.109: E/AndroidRuntime(8632): at android.os.Handler.dispatchMessage(Handler.java:99)
06-14 09:39:23.109: E/AndroidRuntime(8632): at android.os.Looper.loop(Looper.java:137)
06-14 09:39:23.109: E/AndroidRuntime(8632): at android.app.ActivityThread.main(ActivityThread.java:4507)
06-14 09:39:23.109: E/AndroidRuntime(8632): at java.lang.reflect.Method.invokeNative(Native Method)
06-14 09:39:23.109: E/AndroidRuntime(8632): at java.lang.reflect.Method.invoke(Method.java:511)
06-14 09:39:23.109: E/AndroidRuntime(8632): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:790)
06-14 09:39:23.109: E/AndroidRuntime(8632): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:557)
06-14 09:39:23.109: E/AndroidRuntime(8632): at dalvik.system.NativeStart.main(Native Method)
能否请你帮我纠正，以便有相册和显示为ListView控件相关的艺术家我的代码？
问题解决了 ：
对于任何试图填补了专辑，艺术家等的自定义列表视图......与技术LoaderManager / CursorLoader你应该：
1）创建自定义的CursorAdapter结合你的行TextViews到光标处的数据（见我的自定义的CursorAdapter以上）
2）然后，在你的片段这里做什么：
public class AlbumsFragment extends ListFragment implements LoaderManager.LoaderCallbacks<Cursor> {
AlbumsAdapter mAdapter;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View myFragmentView = inflater.inflate(R.layout.albums_fragment_layout, container, false);
return myFragmentView;
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
mAdapter = new AlbumsAdapter(getActivity(), null);
setListAdapter(mAdapter);
getLoaderManager().initLoader(0, null, this);
}
static final String[] ALBUM_SUMMARY_PROJECTION = { MediaStore.Audio.Albums._ID, MediaStore.Audio.Albums.ALBUM, MediaStore.Audio.Albums.ARTIST};
public Loader<Cursor> onCreateLoader(int id, Bundle args) {
String select = null;
return new CursorLoader(getActivity(), MediaStore.Audio.Albums.EXTERNAL_CONTENT_URI,ALBUM_SUMMARY_PROJECTION, select, null, null);
}
public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
mAdapter.swapCursor(data);
}
public void onLoaderReset(Loader<Cursor> loader) {
mAdapter.swapCursor(null);
}
}
这就是它！ 我不知道为什么从来没有人采购有关如何使用LoaderManager，CursorLoader和自定义适配器，以填补自定义列表视图一个非常简单的例子是这样的。 无论如何，我希望这将有助于初学者和我一样的未来。
