A BaseActivity to manage easily the storage permissions in Android

BaseActivity.java

abstract public class BaseActivity extends AppCompatActivity {

    // Storage Permissions variables
    private static final int REQUEST_CODE_EXTERNAL_STORAGE = 1;
    private static String[] PERMISSIONS_STORAGE = {
            Manifest.permission.READ_EXTERNAL_STORAGE,
            Manifest.permission.WRITE_EXTERNAL_STORAGE
    };
    private Runnable mOnWritePermissionGranted;

    public void verifyStoragePermissions(Runnable onPermissionGranted) {
        // Check if we have read or write permission
        mOnWritePermissionGranted = onPermissionGranted;
        int writePermission = ActivityCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE);
        int readPermission = ActivityCompat.checkSelfPermission(this, Manifest.permission.READ_EXTERNAL_STORAGE);

        if (writePermission != PackageManager.PERMISSION_GRANTED || readPermission != PackageManager.PERMISSION_GRANTED) {
            // We don't have permission so prompt the user
            ActivityCompat.requestPermissions(
                    this,
                    PERMISSIONS_STORAGE,
                    REQUEST_CODE_EXTERNAL_STORAGE
            );
        }
        else
            callOnWritePermissionGranted();
    }
    
    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);

        if (requestCode == REQUEST_CODE_EXTERNAL_STORAGE) {
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                callOnWritePermissionGranted();
            } else {
                Toast.makeText(this, "Action cancelled", Toast.LENGTH_LONG).show();
            }
        }
    }

    private void callOnWritePermissionGranted() {
        if(mOnWritePermissionGranted != null){
            mOnWritePermissionGranted.run();
            mOnWritePermissionGranted = null; //reset to prevent future calls issues...
        }
    }
}