Android 6.0 Marshmallow. Cannot write to SD Card

I faced the same problem. There are two types of permissions in Android:

• Dangerous (access to contacts, write to external storage…)
• Normal

Normal permissions are automatically approved by Android while dangerous permissions need to be approved by Android users.

Here is the strategy to get dangerous permissions in Android 6.0

1. Check if you have the permission granted
2. If your app is already granted the permission, go ahead and perform normally.
3. If your app doesn’t have the permission yet, ask for user to approve
4. Listen to user approval in onRequestPermissionsResult

Here is my case: I need to write to external storage.

First, I check if I have the permission:

...
private static final int REQUEST_WRITE_STORAGE = 112;
...
boolean hasPermission = (ContextCompat.checkSelfPermission(activity,
            Manifest.permission.WRITE_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED);
if (!hasPermission) {
    ActivityCompat.requestPermissions(parentActivity,
                new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},
                REQUEST_WRITE_STORAGE);
}

Then check the user’s approval:

@Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
    super.onRequestPermissionsResult(requestCode, permissions, grantResults);
    switch (requestCode)
    {
        case REQUEST_WRITE_STORAGE: {
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED)
            {
                //reload my activity with permission granted or use the features what required the permission
            } else
            {
                Toast.makeText(parentActivity, "The app was not allowed to write to your storage. Hence, it cannot function properly. Please consider granting it this permission", Toast.LENGTH_LONG).show();
            }
        }
    }

}

You can read more about the new permission model here: https://developer.android.com/training/permissions/requesting.html