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PORobust way to pass value back from Dialog to Activity on Android?
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copied!<p>This question has come up several times and I've read all the answers, but I haven't seen a truly robust way to handle this. In my solution, I am using listeners from the calling <code>Activity</code> to the <code>AlertDialog</code> like so:</p> <pre><code>public class MyDialogFragment extends DialogFragment { public interface MyDialogFragmentListener { public void onReturnValue(String foo); } public void init(boolean someValue) { sSomeValue = someValue; listeners = new ArrayList<MyDialogFragmentListener>(); } static boolean sSomeValue; private static ArrayList<MyDialogFragmentListener> listeners; public void addMyDialogFragmentListener(MyDialogFragmentListener l) { listeners.add(l); } public void removeMyDialogFragmentListener(MyDialogFragmentListener l) { listeners.remove(l); } @Override public Dialog onCreateDialog(Bundle savedInstanceState) { AlertDialog.Builder builder = new AlertDialog.Builder(getActivity()); builder.setTitle(R.string.title) .setPositiveButton(R.string.ok, new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int id) { for (MyDialogFragmentListener listener : listeners) { listener.onReturnValue("some value"); } } }) .setNegativeButton(R.string.cancel, new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int id) { // User cancelled the dialog // Nothing to do but exit } }); if (sSomeValue) { builder.setMessage(R.string.some_value_message); } else { builder.setMessage(R.string.not_some_value_message); } // Create the AlertDialog object and return it return builder.create(); } } </code></pre> <p>Then in the calling <code>Activity</code>, I instantiate the object normally, pass in any arguments through <code>init</code> and set my listener.</p> <p>Here's the problem: when you rotate the device and change orientation while the dialog is open, both the <code>Activity</code> and <code>MyDialogFragment</code> objects get re-created. To ensure that the input values don't get screwed up, I am setting my initialized values as <code>static</code>. This feels hacky to me, but since there will only be one such dialog at a time, I am ok with it. Where the problem comes in is with the return value. The original listener will get called. That's fine because the object still exists, but if there is a requirement to update the UI on the <code>Activity</code> (which there is), it won't get updated because the <em>new</em> <code>Activity</code> instance is now controlling the UI.</p> <p>One solution I am considering is casting <code>getActivity()</code> in the dialog class to my <code>Activity</code> and forcing the dialog itself to add a listener, rather than having the calling <code>Activity</code> do it. But this just feels like a snowballing of hacks.</p> <p>What is the best practice for handling this gracefully?</p>

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