应用程序崩溃引发权限拒绝异常：读取com.android.providers.media.MediaProvider

Question

I am developing an app which needs permission to read and write External Storage.i have write all the permissions in Manifest file as well as also in my java activity file but my app still got crashed as soon as it starts with throwing an Exception of

permission denial:reading com.android.providers.media.MediaProvider

Manifest File

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.abhi.scrolling_tab">

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"></uses-permission>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"></uses-permission>
<uses-permission android:name="android.permission.MEDIA_CONTENT_CONTROL"></uses-permission>

<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"
        android:exported="true"
        android:label="@string/app_name"
        android:theme="@style/AppTheme.NoActionBar">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
    <activity
        android:name=".Fragment_one"
        android:label="Fragment_one"
        android:theme="@style/AppTheme.NoActionBar" />
    <activity
        android:name=".Fragment_two"
        android:label="@string/title_activity_fragment_two"
        android:theme="@style/AppTheme.NoActionBar" />
    <activity
        android:name=".Fragment_three"
        android:label="@string/title_activity_fragment_three"
        android:theme="@style/AppTheme.NoActionBar"></activity>
</application>

Java File

public class Fragment_two extends Fragment {
private RecyclerView recyclerView2;
private List<Model1> modelList;
private myAdapter2 adapter;
private MenuItem menu;


public Fragment_two() {
}

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
}

public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.activity_fragment_two, container, false);
    ;
    recyclerView2 = (RecyclerView) view.findViewById(R.id.recycle2);
    int No_of_coloumns = 3;
    recyclerView2.setLayoutManager(new GridLayoutManager(getContext(), No_of_coloumns));
    modelList = getAllaudiofromdevice();
    adapter = new myAdapter2(modelList, (ViewGroup) view);
    recyclerView2.setAdapter(adapter);
    return view;
}

public List<Model1> getAllaudiofromdevice() {
    List<Model1> files = new ArrayList<>();
    try {
        ContentResolver contentResolver = getContext().getContentResolver();
        String selection = MediaStore.Audio.Media.IS_MUSIC;
        Uri uri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
        String[] projection = {MediaStore.Audio.AudioColumns.DATA, MediaStore.Audio.AudioColumns.ALBUM, MediaStore.Audio.AudioColumns.ARTIST};
        Cursor c = contentResolver.query(uri, null, selection, null, null);
        if (c != null) {
            while (c.moveToNext()) {
                Model1 model1 = new Model1();
                String path = c.getString(0);
                String album = c.getString(1);
                String artist = c.getString(2);
                String name = path.substring(path.lastIndexOf('/') + 1);
                model1.setName(name);
                model1.setArtist(artist);
                model1.setAlbum(album);
                model1.setPath(path);
                files.add(model1);
            }
            c.close();
        }
    } catch (Exception e) {
        throw e;
    }
    check();
    return files;
}

public void check() {
    if (Build.VERSION.SDK_INT >= 23) {
        if (ActivityCompat.checkSelfPermission(getActivity(), Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
            requestPermissions(new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, 123);
            return;
        }
    } else {
        getAllaudiofromdevice();
    }
}

@Override
public void onRequestPermissionsResult(int requestcode, @NonNull String[] permissions, @NonNull int[] grantResults) {
    switch (requestcode) {
        case 123:
            if (grantResults[0] != PackageManager.PERMISSION_GRANTED) {
                getAllaudiofromdevice();
            } else {
                Toast.makeText(getContext(), "you have to set permissions", Toast.LENGTH_SHORT).show();
                check();
            }
        default:
            super.onRequestPermissionsResult(requestcode, permissions, grantResults);
    }

}

}

Please help me to get out of this. Thanks in the anticipation.

Answer 1

Only do work when the permission is granted. Your code contains a logical error:

if (grantResults[0] != PackageManager.PERMISSION_GRANTED) { // Mistake here.
    getAllaudiofromdevice();
} //...

Also on API 23 your code will request permissions when they're not granted, but will do nothing(*) when they already are granted. It should be like this:

public void check() {
    if (Build.VERSION.SDK_INT >= 23 && ActivityCompat.checkSelfPermission(getActivity(), Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
        // Request permissions if they're not granted on API 23.
        requestPermissions(new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, 123);
    } else {
        // Do work on API <23 and when permissions were granted on API 23+.
        getAllaudiofromdevice();
    }
}

(*) Depending on how you call your code, it's really confusing.