DialogFragment callback on orientation change

Question

I'm migrating my dialogs, currently using Activity.showDialog(DIALOG_ID);, to use the DialogFragment system as discussed in the android reference.

There's a question that arose during my development when using callbacks to deliver some event back to the activity/fragment that opened the dialog:

Here's some example code of a simple dialog:

public class DialogTest extends DialogFragment {

public interface DialogTestListener {
    public void onDialogPositiveClick(DialogFragment dialog);
}

// Use this instance of the interface to deliver action events
static DialogTestListener mListener;

public static DialogTest newInstance(Activity activity, int titleId, int messageId) {
    udateListener(activity);
    DialogTest frag = new DialogTest();
    Bundle args = new Bundle();
    args.putInt("titleId", titleId);
    args.putInt("messageId", messageId);
    frag.setArguments(args);
    return frag;
}

public static void udateListener(Activity activity) {
    try {
        // Instantiate the NoticeDialogListener so we can send events with it
        mListener = (DialogTestListener) activity;
    } catch (ClassCastException e) {
        // The activity doesn't implement the interface, throw exception
        throw new ClassCastException(activity.toString() + " must implement DialogTestListener");
    }
}


@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
    int titleId = getArguments().getInt("titleId");
    int messageId = getArguments().getInt("messageId");

    AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
    // dialog title
    builder.setTitle(titleId);
    // dialog message
    builder.setMessage(messageId);

    // dialog negative button
    builder.setNegativeButton("No", new OnClickListener() {
               public void onClick(DialogInterface dialog, int id) {}});
    // dialog positive button
    builder.setPositiveButton("Yes", new OnClickListener() {
        public void onClick(DialogInterface dialog, int id) {
            mListener.onDialogPositiveClick(DialogTest.this);
        }});

    // create the Dialog object and return it
    return builder.create();
}}

And here's some activity code calling it:

public class SomeActivity extends FragmentActivity implements DialogTestListener {
private EditText mUserName;
@Override
public void onCreate(Bundle savedInstanceState) {
    // setup ui
    super.onCreate(savedInstanceState);
    setContentView(R.layout.ui_user_edit);
    // name input
    mUserName = (EditText) findViewById(R.id.userEdit_editTextName);
}

@Override
public void onDialogPositiveClick(DialogFragment dialog) {
    Log.d(TAG, this.toString());
    mUserName.setText(mUserName.getText() + "1");
}

private void showDialog() {
    DialogTest test = DialogTest.newInstance(SomeActivity.this, R.string.someTitleText, R.string.someMessageText);
    test.show(getSupportFragmentManager(), "testDialog");
}}

The code is pretty much what you see the reference. Problem is, that once you do a orientation change, when a dialog is shown, it stops working as expected --> Due to the activity lifecycle, both, the activity and the dialog are rebuild, and the dialog now does not have the proper reference to the new rebuilt activity.

I added the following code to my activitys onResume method:

    @Override
protected void onResume() {
    super.onResume();
    DialogTest.udateListener(this);
}

Doing this, I get the expected behavior, and the dialog sends events back to the new rebuilt activity when an orientation change occured.

My question is: What is the 'best practice' to handle the callbacks between the DialogFragment which was opened by a FragmentActivity during an orientation change?

Best regards

Answer 1

There is better solution instead of using static methods and variables because it would work only fro one instance of your dialog. It is better to store your callback as non static member

private DialogTestListener mListener;
public void setListener (DialogTestListener listener){
  mListener = listener;
}

Then you should show your dialog using TAG like this mDialogFragment.show(getSupportFragmentManager(), DIALOG_TAG);

And then in onResume method of your activity you can reset your listener

protected void onResume() {
   super.onResume();
   mDialogFragment = (CMFilterDialogFrg) getSupportFragmentManager().findFragmentByTag(DIALOG_TAG);
   if(mDialogFragment  != null){
       mDialogFragment.setListener(yourListener)
   }
}