权限无法访问Android的外部存储

Question

I'm trying to find all mp3 files in storage but my app is crashing and I used the logcat to see why and comes with problem with permission to access external storage but I already put the permission on manifest and I dont no why keep crashing. First error:

03-06 14:55:24.553: E/dex2oat(2796): Failed to create oat file: /data/dalvik-cache/x86/data@app@felipe.cursoandroid.com.musicbox-2@split_lib_dependencies_apk.apk@classes.dex: Permission denied

and more errors:

03-06 14:55:25.274: E/DatabaseUtils(1873): Writing exception to parcel 03-06 14:55:25.274: E/DatabaseUtils(1873): java.lang.SecurityException: Permission Denial: reading com.android.providers.media.MediaProvider uri content://media/external/audio/media from pid=2783, uid=10057 requires android.permission.READ_EXTERNAL_STORAGE, or grantUriPermission() 03-06 14:55:25.274: E/DatabaseUtils(1873): at android.content.ContentProvider.enforceReadPermissionInner(ContentProvider.java:605) 03-06 14:55:25.274: E/DatabaseUtils(1873): at android.content.ContentProvider$Transport.enforceReadPermission(ContentProvider.java:480) 03-06 14:55:25.274: E/DatabaseUtils(1873): at android.content.ContentProvider$Transport.query(ContentProvider.java:211) 03-06 14:55:25.274: E/DatabaseUtils(1873): at android.content.ContentProviderNative.onTransact(ContentProviderNative.java:112) 03-06 14:55:25.274: E/DatabaseUtils(1873): at android.os.Binder.execTransact(Binder.java:453)

My MainActivity.java :

public class MainActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    SongsManager songsManager = new SongsManager();
    songsManager.getSongs(this);
    ArrayList<Song> songList = songsManager.getSongsList();
    ArrayAdapter<Song> adapterSongList = new ArrayAdapter<Song>(this, android.R.layout.simple_list_item_1, songList);
    ListView listView = (ListView) findViewById(R.id.musicList);
    listView.setAdapter(adapterSongList);
}
}

My SongsManager.java :

public class SongsManager {

private ArrayList<Song> songsList;
public ArrayList<Song> getSongsList(){
    return songsList;
}
public void getSongs(Context ctx){
    ContentResolver musicResolver = ctx.getContentResolver();
    Uri musicUri = android.provider.MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
    Cursor musicCursor = musicResolver.query(musicUri, null, null, null, null);
    if(musicCursor!=null && musicCursor.moveToFirst()){
        //get columns
        int titleColumn = musicCursor.getColumnIndex(android.provider.MediaStore.Audio.Media.TITLE);
        int idColumn = musicCursor.getColumnIndex(android.provider.MediaStore.Audio.Media._ID);
        int artistColumn = musicCursor.getColumnIndex(android.provider.MediaStore.Audio.Media.ARTIST);
        int pathConlumn = musicCursor.getColumnIndex(android.provider.MediaStore.Audio.Media.DATA);
        do {
            long thisId = musicCursor.getLong(idColumn);
            String thisTitle = musicCursor.getString(titleColumn);
            String thisArtist = musicCursor.getString(artistColumn);
            String thisPath = musicCursor.getString(pathConlumn);
            songsList.add(new Song(thisId, thisTitle, thisArtist, thisPath));
        }
        while (musicCursor.moveToNext());
    }
}
}

my manifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="felipe.cursoandroid.com.musicbox">
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>


</manifest>

Answer 1

which android version you use? pay attention that for 6+ you should ask permissions on runtime

Answer 2

If you are using android 23+.Then I can tell that your issue is that you need to manage the permissions explicitly.Reading/Writing to Storage are considered to be dangerous permissions. Here you can learn how to manage that: https://developer.android.com/training/permissions/requesting.html

You can to run your app on Android API-22 or bellow. It should be working there.