Android. Read files of external storage

Question

I try to get files from external storage by this program:

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        TextView textView = findViewById(R.id.textView);
        StringBuilder builder = new StringBuilder();
        File specFile = Environment.getExternalStorageDirectory();

        builder.append(Environment.getExternalStorageState() + "\n");
        if (specFile.exists()) {
            builder.append(specFile);
            if (specFile.list() != null) {
                String[] files = specFile.list();
                for (int i = 0; i < files.length; i++) {
                    builder.append(files[i] +"\n");
                }
            } else {
                builder.append(" exist but empty\n");
            }
        }
        builder.append("/storage/emulated/0/Android exist: " + new File("/storage/emulated/0/Android").exists());
        textView.setText(builder);
    }
}

This permissions was added:

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

It works good in emulator, but in the real phone it returns null when I try to get list. It also can normally find dirs in storage.

Answer 1

Problem resolved by adding this code:

int requestCode = 0;

if (Build.VERSION.SDK_INT >= 23) {
    if(checkSelfPermission(Manifest.permission.READ_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED){
        requestPermissions(new String[]{Manifest.permission.READ_EXTERNAL_STORAGE}, requestCode);
    }
}