How to get read external storage permissions?

问题

I'm developing an mp3 player application for android and I'm getting an error related to user permissions(READ_EXTERNAL_STORAGE)

This is my code where I ask for permissions:

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

        if (ContextCompat.checkSelfPermission(PlayListActivity.this,
                Manifest.permission.READ_EXTERNAL_STORAGE)
                != PackageManager.PERMISSION_GRANTED) {


            // OPCIONAL(explicaciones de poque pedimos los permisos)
            if (ActivityCompat.shouldShowRequestPermissionRationale(PlayListActivity.this,
                    Manifest.permission.READ_EXTERNAL_STORAGE)) {

            } else {
                //pedir permisos
                ActivityCompat.requestPermissions(PlayListActivity.this,
                        new String[]{Manifest.permission.READ_EXTERNAL_STORAGE},
                        permissionCheck);

and this is the rest of the code:

ArrayList<HashMap<String, String>> songsListData = new ArrayList<HashMap<String, String>>();

    SongsManager plm = new SongsManager(PlayListActivity.this);
    // get all songs from sdcard
    this.songsList = plm.getPlayList();

    // looping through playlist
    for (int i = 0; i < songsList.size(); i++) {
        // creating new HashMap
        HashMap<String, String> song = songsList.get(i);

        // adding HashList to ArrayList
        songsListData.add(song);
    }

    // se añaden las canciones a la ListView mediante un adapter utilizando el layout playlist_item
    ListAdapter adapter = new SimpleAdapter(this, songsListData,
            R.layout.playlist_item, new String[] { "songTitle" }, new int[] {
            R.id.songTitle });

    setListAdapter(adapter);

this is the error:

03-31 22:09:16.159 2258-2258/com.androidchatapp E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.androidchatapp, PID: 2258
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.androidchatapp/com.androidchatapp.PlayListActivity}: java.lang.SecurityException: Permission Denial: reading com.android.providers.media.MediaProvider uri content://media/external/audio/media from pid=2258, uid=10184 requires android.permission.READ_EXTERNAL_STORAGE, or grantUriPermission()
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2434)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2494)
    at android.app.ActivityThread.access$900(ActivityThread.java:153)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1347)
    at android.os.Handler.dispatchMessage(Handler.java:102)
    at android.os.Looper.loop(Looper.java:148)
    at android.app.ActivityThread.main(ActivityThread.java:5451)
    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: java.lang.SecurityException: Permission Denial: reading com.android.providers.media.MediaProvider uri content://media/external/audio/media from pid=2258, uid=10184 requires android.permission.READ_EXTERNAL_STORAGE, or grantUriPermission()
    at android.os.Parcel.readException(Parcel.java:1620)
    at android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:183)
    at android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:135)
    at android.content.ContentProviderProxy.query(ContentProviderNative.java:421)
    at android.content.ContentResolver.query(ContentResolver.java:493)
    at android.content.ContentResolver.query(ContentResolver.java:435)
    at com.androidchatapp.SongsManager.getPlayList(SongsManager.java:48)
    at com.androidchatapp.PlayListActivity.onCreate(PlayListActivity.java:65)
    at android.app.Activity.performCreate(Activity.java:6323)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1108)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2387)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2494)
    at android.app.ActivityThread.access$900(ActivityThread.java:153)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1347)
    at android.os.Handler.dispatchMessage(Handler.java:102)
    at android.os.Looper.loop(Looper.java:148)
    at android.app.ActivityThread.main(ActivityThread.java:5451)
    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)

回答1:

You have asked the permission from the code , but you are probably forgetting to add this permission tag in the manifest file

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

回答2:

Android introduce runtime permission from Marshmallow OS, so we need to implement runtime permission with Manifest permission. if CompileSdkVersion = 23

You can ask permission when your screen open (in onCreate()) or click event of your button (Like -play Music )

use this method for check runtime Permission is enable or not

 public boolean checkPermissionForReadExtertalStorage() {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            int result = context.checkSelfPermission(Manifest.permission.READ_EXTERNAL_STORAGE);
            return result == PackageManager.PERMISSION_GRANTED;
        }
        return false;
    }

if it return false then call below method, it will show a dialog for permission

 public void requestPermissionForReadExtertalStorage() throws Exception {
        try {
            ActivityCompat.requestPermissions((Activity) context, new String[]{Manifest.permission.READ_EXTERNAL_STORAGE},
                    READ_STORAGE_PERMISSION_REQUEST_CODE);
        } catch (Exception e) {
            e.printStackTrace();
            throw e;
        }
    }

来源：https://stackoverflow.com/questions/43148879/how-to-get-read-external-storage-permissions