我正在制作一个包含多个标签（歌曲，播放列表，专辑等）的音乐播放器应用。每个代表一个片段。截至目前，我未能使用媒体商店创建一个偶数歌曲列表。
这是我尝试的代码，但它无效
public class Songs extends ListFragment implements LoaderManager.LoaderCallbacks<Cursor> {
SongsAdapter mAdapter;
private static final String ARG_POSITION = "position";
private int position;
public static Songs newInstance(int position) {
Songs f = new Songs();
Bundle b = new Bundle();
b.putInt(ARG_POSITION, position);
f.setArguments(b);
return f;
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View myFragmentView = inflater.inflate(R.layout.songs, container, false);
return myFragmentView;
}
@Override
public void onActivityCreated(Bundle savedInstanceState)
{
super.onActivityCreated(savedInstanceState);
mAdapter = new SongsAdapter(getActivity(), null);
setListAdapter(mAdapter);
getLoaderManager().initLoader(0, null, this);
}
static final String[] SONGS_SUMMARY_PROJECTION = { MediaStore.Audio.Media._ID,MediaStore.Audio.Media.TITLE, MediaStore.Audio.Media.ALBUM_ID, MediaStore.Audio.Media.DURATION};
public Loader<Cursor> onCreateLoader(int id, Bundle args) {
String select = null;
return new CursorLoader(getActivity(), MediaStore.Audio.Media.EXTERNAL_CONTENT_URI,SONGS_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);
}
}
这是适配器类
public class SongsAdapter extends CursorAdapter {
private final LayoutInflater nInflater;
public SongsAdapter(Context context, Cursor c) {
super(context, c);
nInflater = LayoutInflater.from(context);
}
@Override
public void bindView(View view, Context context, Cursor cursor) {
cursor.moveToFirst();
TextView songTitle = (TextView) view.findViewById(R.id.songTitle);
songTitle.setText(cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.TITLE)));
TextView artist = (TextView) view.findViewById(R.id.songArtist);
artist.setText(cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.ARTIST)));
ImageView albumArt = (ImageView) view.findViewById(R.id.list_image);
albumArt.setScaleType(ImageView.ScaleType.FIT_XY);
Long albumId = cursor.getLong(cursor.getColumnIndexOrThrow(MediaStore.Audio.Media.ALBUM_ID));
Bitmap img = getAlbumart(context,albumId);
if(img != null)
albumArt.setImageBitmap(img);
else{
Bitmap def = getDefaultAlbumArt(context);
albumArt.setImageBitmap(def);
}
}
@Override
public View newView(Context context, Cursor cursor, ViewGroup parent) {
final View view = nInflater.inflate(R.layout.song_item, parent, false);
return view;
}
public Bitmap getAlbumart(Context context, Long album_id) {
Bitmap bm = null;
try {
final Uri sArtworkUri = Uri
.parse("content://media/external/audio/albumart");
Uri uri = ContentUris.withAppendedId(sArtworkUri, album_id);
ParcelFileDescriptor pfd = context.getContentResolver()
.openFileDescriptor(uri, "r");
if (pfd != null) {
FileDescriptor fd = pfd.getFileDescriptor();
bm = BitmapFactory.decodeFileDescriptor(fd);
}
} catch (Exception e) {
}
return bm;
}
public Bitmap getDefaultAlbumArt(Context context) {
Bitmap bm = null;
BitmapFactory.Options options = new BitmapFactory.Options();
try {
bm = BitmapFactory.decodeResource(context.getResources(),
R.drawable.musicicon, options);
} catch (Error ee) {
} catch (Exception e) {
}
return bm;
}
}
这里是logcat消息：
java.lang.IllegalStateException: Couldn't read row 0, col -1 from CursorWindow. Make sure the Cursor is initialized correctly before accessing data from it.
at android.database.CursorWindow.nativeGetString(Native Method)
at android.database.CursorWindow.getString(CursorWindow.java:434)
at android.database.AbstractWindowedCursor.getString(AbstractWindowedCursor.java:62)
at android.database.CursorWrapper.getString(CursorWrapper.java:114)
at com.screens.SongsAdapter.bindView(SongsAdapter.java:42)
at android.widget.CursorAdapter.getView(CursorAdapter.java:254)
at android.widget.AbsListView.obtainView(AbsListView.java:2338)
at android.widget.ListView.measureHeightOfChildren(ListView.java:1273)
at android.widget.ListView.onMeasure(ListView.java:1182)
at android.view.View.measure(View.java:16838)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5374)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:340)
at android.view.View.measure(View.java:16838)
at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1455)
at android.view.View.measure(View.java:16838)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:926)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:607)
at android.view.View.measure(View.java:16838)
at android.support.v4.widget.DrawerLayout.onMeasure(DrawerLayout.java:868)
at android.view.View.measure(View.java:16838)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5374)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:340)
at android.support.v7.internal.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:124)
at android.view.View.measure(View.java:16838)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5374)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1621)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:742)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:607)
at android.view.View.measure(View.java:16838)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5374)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:340)
at android.view.View.measure(View.java:16838)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5374)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1621)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:742)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:607)
at android.view.View.measure(View.java:16838)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5374)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:340)
at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2332)
at android.view.View.measure(View.java:16838)
at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2252)
at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1315)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1513)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1192)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6231)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:788)
at android.view.Choreographer.doCallbacks(Choreographer.java:591)
at android.view.Choreographer.doFrame(Choreographer.java:560)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:774)
at android.os.Handler.handleCallback(Handler.java:808)
at android.os.Handler.dispatchMessage(Handler.java:103)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:5292)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:824)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:640)
at dalvik.system.NativeStart.main(Nativ
请告诉我需要对这些代码进行哪些修改。
如果可能的话，请告诉我如何在点击列表中的歌曲时启动播放器。需要添加什么方法？
答案 0 :(得分：0)
代码mAdapter = new SongsAdapter(getActivity(), null)不正确。通常，您在第二个参数上传递Cursor对象。
代码示例：
Cursor todoCursor = db.rawQuery("SELECT * FROM todo_items", null);
TodoCursorAdapter todoAdapter = new TodoCursorAdapter(this, todoCursor);
示例代码来自教程Populating a ListView with a CursorAdapter。
这样，cursor.moveToFirst();中代码bindView()中的光标对象将有效。但是你必须执行数据库查询。