android - 音乐播放器请求写入外部存储权限？

Question

我正在 Android 中创建一个音乐播放器应用程序。它工作正常但是每当我在歌曲列表中滚动时它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 list 文件中授予写权限时，这个问题就消失了，但我不明白的是为什么它在我不写的时候要求WriteExternalStoragePermission任何类型的存储。据我了解，音乐播放器不需要写入外部存储权限。

这是歌曲列表 Activity 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;
    }
}

它在这一行异常崩溃

bitmap = MediaStore.Images.Media.getBitmap(ctx.getContentResolver(), uri);

在这段代码中，我获得了相应 mp3 文件的专辑封面。但是这段代码也只是从外部存储读取，因此这也不应该请求写入权限，因为我只是在读取位图而不是写入它。

Answer 1

来自 the MediaProvider code ，处理“/media/external/audio/albumart”

内部 openFile(Uri uri, String mode)

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，它会调用 getThumb

getThumb 调用 makeThumbInternal

然后在特定条件下，它调用

writeAlbumArt(need_to_recompress, out, compressed, bm);

在最新版本中，writeAlbumArt 调用

final long identity = Binder.clearCallingIdentity();

写之前，应该可以解决问题。但是修复是在 2015 年 8 月 27 日提交的，因此只有 Marshmallow 有机会获得修复。