我正在Android中创建一个音乐播放器应用程序。它工作得很好，但每当我在歌曲列表中滚动时，它就会开始崩溃，并给出这个异常
Process: com.example.lenovo.musicplayer, PID: 31100
java.lang.SecurityException: External path: /storage/emulated/0/Android/data/com.android.providers.media/albumthumbs/1460104607336: Neither user 10294 nor current process has android.permission.WRITE_EXTERNAL_STORAGE.
at android.os.Parcel.readException(Parcel.java:1555)
at android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:190)
at android.database.DatabaseUtils.readExceptionWithFileNotFoundExceptionFromParcel(DatabaseUtils.java:153)
at android.content.ContentProviderProxy.openTypedAssetFile(ContentProviderNative.java:691)
at android.content.ContentResolver.openTypedAssetFileDescriptor(ContentResolver.java:1170)
at android.content.ContentResolver.openAssetFileDescriptor(ContentResolver.java:994)
at android.content.ContentResolver.openInputStream(ContentResolver.java:719)
at android.provider.MediaStore$Images$Media.getBitmap(MediaStore.java:1110)
at com.example.lenovo.musicplayer.Adapter.getView(Adapter.java:119)
at android.widget.AbsListView.obtainView(AbsListView.java:2571)
at android.widget.ListView.makeAndAddView(ListView.java:1894)
at android.widget.ListView.fillDown(ListView.java:710)
at android.widget.ListView.fillGap(ListView.java:674)
at android.widget.AbsListView.trackMotionScroll(AbsListView.java:5900)
at android.widget.AbsListView$FlingRunnable.run(AbsListView.java:5378)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:825)
at android.view.Choreographer.doCallbacks(Choreographer.java:619)
at android.view.Choreographer.doFrame(Choreographer.java:578)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:811)
at android.os.Handler.handleCallback(Handler.java:815)
at android.os.Handler.dispatchMessage(Handler.java:104)
at android.os.Looper.loop(Looper.java:214)
at android.app.ActivityThread.main(ActivityThread.java:6102)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1028)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:823)
当我在清单文件中授予写入权限时，这个问题就会消失，但我不明白的是为什么当我没有向任何类型的存储写入任何内容时，它会请求WriteExternalStoragePermission。据我所知，音乐播放器不需要写入外部存储权限。
这是歌曲列表活动的代码
public class ActivitySongsList extends AppCompatActivity {
public static ArrayList<MusicBean>songsList;
ListView listView;
Toolbar toolbar;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_songs_list);
toolbar= (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
listView= (ListView) findViewById(R.id.lv_songs);
songsList=getAudioList();
Adapter adapter=new Adapter(this,songsList);
listView.setAdapter(adapter);
getSupportActionBar().setTitle("Songs");
toolbar.setTitleTextColor(Color.parseColor("#ffffff"));
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Intent intent=new Intent(ActivitySongsList.this,ActivityMusicDetails.class);
intent.putExtra("song",songsList.get(position));
intent.putExtra("position",String.valueOf(position));
startActivity(intent);
}
});
}
private ArrayList<MusicBean> getAudioList() {
ArrayList<MusicBean> musicBeanArrayList=new ArrayList<>();
try {
final Cursor mCursor = getContentResolver().query(
MediaStore.Audio.Media.EXTERNAL_CONTENT_URI,
new String[]{MediaStore.Audio.Media.DISPLAY_NAME, MediaStore.Audio.Media.DATA, MediaStore.Audio.Media.ALBUM_ID,MediaStore.Audio.Media.ARTIST,MediaStore.Audio.Media.TITLE}, null, null,
"LOWER(" + MediaStore.Audio.Media.TITLE + ") ASC");
int count = mCursor.getCount();
int i = 0;
if (mCursor.moveToFirst()) {
do {
String song=mCursor.getString(mCursor.getColumnIndexOrThrow(MediaStore.Audio.Media.TITLE));
String path=mCursor.getString(mCursor.getColumnIndexOrThrow(MediaStore.Audio.Media.DATA));
long album_id=mCursor.getLong(mCursor.getColumnIndexOrThrow(MediaStore.Audio.Media.ALBUM_ID));
String artist=mCursor.getString(mCursor.getColumnIndexOrThrow(MediaStore.Audio.Media.ARTIST));
Uri sArtworkUri = Uri
.parse("content://media/external/audio/albumart");
Uri albumArtUri = ContentUris.withAppendedId(sArtworkUri, album_id);
musicBeanArrayList.add(new MusicBean(song,path,albumArtUri.toString(),String.valueOf(album_id),artist));
/*songs[i] = mCursor.getString(mCursor.getColumnIndexOrThrow(MediaStore.Audio.Media.DISPLAY_NAME));
mAudioPath[i] = mCursor.getString(mCursor.getColumnIndexOrThrow(MediaStore.Audio.Media.DATA));*/
i++;
} while (mCursor.moveToNext());
}
mCursor.close();
}catch (Exception e)
{
e.printStackTrace();
}
return musicBeanArrayList;
}
}
它崩溃了，这条线上出现了异常
bitmap = MediaStore.Images.Media.getBitmap(ctx.getContentResolver(), uri);
在这个代码中，我得到了相应mp3文件的专辑艺术。但这段代码也只是从外部存储读取，因此也不应该请求写入权限，因为我只读取位图而不是写入位图。
来自处理"/media/external/audio/albumart"的MediaProvider代码
openFile(Uri uri, String mode) 内部
try {
pfd = openFileAndEnforcePathPermissionsHelper(newUri, mode);
} catch (FileNotFoundException ex) {
// That didn't work, now try to get it from the specific file
pfd = getThumb(database, db, audiopath, albumid, null);
}
因此，如果找不到文件，它将调用getThumb
getThumb调用makeThumbInternal
然后在某些条件下，它调用
writeAlbumArt(need_to_recompress, out, compressed, bm);
在最新版本中，writeAlbumArt调用
final long identity = Binder.clearCallingIdentity();
在写作之前，这应该可以解决问题。但修复是在2015年8月27日提交的，所以只有棉花糖有机会获得修复。
需要它，因为MediaStore需要它，没有READ-ONLY；MediaStore正在访问您的行为上的外部文件，所以是您在进行读取。
您可以使用folling链接https://github.com/android/platform_packages_providers_mediaprovider/blob/master/src/com/android/providers/media/MediaProvider.java是为你提供帮助。。
在清单文件中声明权限如下：
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />