android - 在运行时拒绝和授予权限后在 Android 应用程序上获取 FileNotFoundException

Question

我正在尝试获取一个应用程序来播放 SD 卡中的 mp3。我在 Windows 8 上使用 android sdk 版本 23 和 Android studio。我在 nexus 5 模拟器上运行它。

我在运行时请求权限，如果我拒绝一次权限但在第二次请求时授予权限，我将收到 FileNotFoundException。如果我重新启动应用程序，我就可以播放音乐文件，如果我在第一次尝试时接受权限请求，它也会成功播放音乐而无需重新启动。

我制作了一个简单的程序来重现该问题并将其发布在 github 上.您需要/Music 目录中的 mp3 文件才能运行此应用程序。

这是我请求存储权限的代码:

 private void CheckPermission() {

    int permissionCheck = ContextCompat.checkSelfPermission(this, Manifest.permission.READ_EXTERNAL_STORAGE);

    if (permissionCheck == PackageManager.PERMISSION_GRANTED) {
        playSong();
    } else {
        // we don't have permission, request it
        ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.READ_EXTERNAL_STORAGE},
                REQUEST_EXTERNAL_STORAGE_PERMISSION);

    }
}

@Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
    switch (requestCode) {
        case REQUEST_EXTERNAL_STORAGE_PERMISSION:
            if (grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                // Permission Granted
                Toast.makeText(getApplicationContext(), "Storage access granted, touch screen to start music", Toast.LENGTH_SHORT)
                        .show();
            } else {
                // Permission Denied
                Toast.makeText(getApplicationContext(), "Storage access denied, can't load music", Toast.LENGTH_SHORT)
                        .show();
            }
            break;
        default:
            super.onRequestPermissionsResult(requestCode, permissions, grantResults);
    }
}

这是失败的相关代码 fragment :

 Uri uri = android.provider.MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
    String projection[] =
            {android.provider.MediaStore.Audio.Media.DATA, android.provider.MediaStore.Audio.Media.TITLE};
    Cursor cursor = this.getContentResolver().query(uri, projection, null, null, null);
    String songURI = new String();
    String title = new String();

    while (cursor.moveToNext()) {
        String data = cursor.getString(0);
        title = cursor.getString(1);
        // Note: Look for music folder in root drive.
        if (data.matches("^/storage/emulated/0/Music/.*")) {
            songURI = data;
            break;
        }
    }
    if (cursor != null) {
        cursor.close();
    }

    if (mediaPlayer != null) {
        mediaPlayer.stop();
        mediaPlayer.release();
        mediaPlayer = null;
    }

    mediaPlayer = MediaPlayer.create(getApplicationContext(), Uri.parse(songURI));

    try
    {
        mediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
        mediaPlayer.start();
        Toast toast = Toast.makeText(getApplicationContext(), title, Toast.LENGTH_SHORT);
        toast.show();
    } catch (Exception e) {
        // TODO: handle exception
        e.printStackTrace();
        return;
    }

这里是堆栈跟踪:

MediaPlayer: create failed: java.io.FileNotFoundException: /storage/emulated/0/Music/108-radiohead-house of cards-pms.mp3: open failed: EACCES (Permission denied) at libcore.io.IoBridge.open(IoBridge.java:452) at java.io.FileInputStream.(FileInputStream.java:76) at android.media.MediaPlayer.setDataSource(MediaPlayer.java:1095) at android.media.MediaPlayer.setDataSource(MediaPlayer.java:1074) at android.media.MediaPlayer.setDataSource(MediaPlayer.java:1028) at android.media.MediaPlayer.setDataSource(MediaPlayer.java:973) at android.media.MediaPlayer.create(MediaPlayer.java:880) at android.media.MediaPlayer.create(MediaPlayer.java:857) at android.media.MediaPlayer.create(MediaPlayer.java:836) at gunboat.com.mediaplayererror.FullscreenActivity.playSong(FullscreenActivity.java:190) at gunboat.com.mediaplayererror.FullscreenActivity.CheckPermission(FullscreenActivity.java:135) at gunboat.com.mediaplayererror.FullscreenActivity.access$300(FullscreenActivity.java:24) at gunboat.com.mediaplayererror.FullscreenActivity$5.onClick(FullscreenActivity.java:113) at android.view.View.performClick(View.java:5198) at android.view.View$PerformClick.run(View.java:21147) at android.os.Handler.handleCallback(Handler.java:739) at android.os.Handler.dispatchMessage(Handler.java:95) at android.os.Looper.loop(Looper.java:148) at android.app.ActivityThread.main(ActivityThread.java:5417) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) Caused by: android.system.ErrnoException: open failed: EACCES (Permission denied) at libcore.io.Posix.open(Native Method) at libcore.io.BlockGuardOs.open(BlockGuardOs.java:186) at libcore.io.IoBridge.open(IoBridge.java:438) at java.io.FileInputStream.(FileInputStream.java:76)  at android.media.MediaPlayer.setDataSource(MediaPlayer.java:1095)  at android.media.MediaPlayer.setDataSource(MediaPlayer.java:1074)  at android.media.MediaPlayer.setDataSource(MediaPlayer.java:1028)  at android.media.MediaPlayer.setDataSource(MediaPlayer.java:973)  at android.media.MediaPlayer.create(MediaPlayer.java:880)  at android.media.MediaPlayer.create(MediaPlayer.java:857)  at android.media.MediaPlayer.create(MediaPlayer.java:836)  at gunboat.com.mediaplayererror.FullscreenActivity.playSong(FullscreenActivity.java:190)  at gunboat.com.mediaplayererror.FullscreenActivity.CheckPermission(FullscreenActivity.java:135)  at gunboat.com.mediaplayererror.FullscreenActivity.access$300(FullscreenActivity.java:24)  at gunboat.com.mediaplayererror.FullscreenActivity$5.onClick(FullscreenActivity.java:113)  at android.view.View.performClick(View.java:5198)  at android.view.View$PerformClick.run(View.java:21147)  at android.os.Handler.handleCallback(Handler.java:739)  at android.os.Handler.dispatchMessage(Handler.java:95)  at android.os.Looper.loop(Looper.java:148)  at android.app.ActivityThread.main(ActivityThread.java:5417) 

Answer 1

今天刚刚解决了这个问题。您需要在授予权限后重新启动您的应用程序。我用这样的东西来完成重启:

private static final int REQUEST_CODE_READ_EXTERNAL_STORAGE = 1;

@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
    switch (requestCode) {
        case REQUEST_CODE_READ_EXTERNAL_STORAGE:
            if (grantResults.length >= 1 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                // Schedule start after 1 second
                PendingIntent pi = PendingIntent.getActivity(this, 0, getIntent(), PendingIntent.FLAG_CANCEL_CURRENT);
                AlarmManager am = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
                am.set(AlarmManager.RTC, System.currentTimeMillis() + 1000, pi);

                // Stop now
                System.exit(0);
            } else {
                Toast.makeText(this, R.string.error_external_storage_unavailable, Toast.LENGTH_LONG).show();
                finish();
            }

            break;
    }

    super.onRequestPermissionsResult(requestCode, permissions, grantResults);
}

这是我曾经得出这个结论的来源:Application not able to access SD card when WRITE_EXTERNAL_STORAGE permission is granted at run time

重新启动的原因是，当授予 READ_EXTERNAL_STORAGE 或 WRITE_EXTERNAL_STORAGE 权限时，您的应用程序的用户帐户被添加到新的安全组。当应用程序进程仍在运行时，此更改不会生效。