Android: Under what circumstances would a Dialog appearing cause onPause() to be called?

A snippet from the Android Activities document(scroll down to the "foreground lifetime" line) says :

An activity can frequently transition in and out of the foreground—for example, onPause() is called when the device goes to sleep or when a dialog appears.

I don't quite understand this. Under what circumstances should this happen? Is onPause() called only if the context of the dialog in question is different from the activity on top of which the dialog is to be displayed?

EDIT: Adding code sample to illustrate my doubt in detail

Going by the above-mentioned quote from document, should my activity's onPause() method get called when the AlertDialog (or just the Dialog) in the following code gets displayed? Should I see the "onPause called" log entry when the dialog is displayed?

But I don't see that happen. And it shouldn't either, if I have understood the Android life cycle correctly! So, what's the document pointing at then?

public class LifeCycleTestActivity extends Activity {

    private static final String TAG = "LifeCycleTest";

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        Button btn = (Button) findViewById(R.id.button1);

        btn.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                Log.d(TAG, "onClick");

                AlertDialog dialog = new AlertDialog.Builder(LifeCycleTestActivity.this).create();
                 dialog.setMessage("You Clicked on the button");
                 dialog.setTitle("Dialog!");
                 dialog.setButton(AlertDialog.BUTTON_NEUTRAL, "OK", new DialogInterface.OnClickListener() {

                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        dialog.dismiss();
                    }
                });
                 dialog.setCancelable(true);
                 dialog.show();


                /*
                Dialog dialog = new Dialog(LifeCycleTestActivity.this);
                 dialog.setTitle("Dialog!");
                 dialog.setCancelable(true);
                 dialog.show();
                */
            }
        });        
    }

    @Override
    protected void onPause() {
        Log.d(TAG, "onPause() called");
        super.onPause();

    }

    @Override
    protected void onResume() {
        super.onResume();
        Log.d(TAG, "onResume() called");
    }
}

onPause() is called when your activity is no longer at the top of the activity stack. A Dialog by itself is not an Activity, so will not replace the current Activity at the top of the stack, so will not cause anything to pause.

A dialog (lower-case) does not need to be implemented by a Dialog class, however. For example, it is not uncommon to implement one with an Activity whose theme is set to that of a dialog. In this case, displaying the dialog-as-an-Activity will cause the new Activity to be on the top of the stack, pausing what previously was there.

I've been doing quite a lot of code with dialogs, including the AlertDialog that you mention, and I've also tried to check if onPause() is being called on the activity when the dialog pops up, but thus far my conclusion is that the activity simply keeps running and that onPause() is not called.

Not sure if it helps, but at least you now know that there are others who experience what you're experiencing :-)

Its wrong that activity remains no longer at top of activity stack in onPause phase.

Condition an activity to be onPause state -

• Activity partially visible e.g. dialog on activity.

• The Activity object is retained in memory, it maintains all state and member information, and remains attached to the window manager.

  e.g Home button pressed causes activity to go in onPause(). Still at top of stack.

In fig 1. Activity3 will be destroyed and removed from top stack

In fig 2. Now Task A goes to background but Activty X still on top of stack . If you override onPause() method int this state

Figure 1. A representation of how each new activity in a task adds an item to the back stack. When the user presses the Back button, the current activity is destroyed and the previous activity resumes.

Figure 2. Two tasks: Task B receives user interaction in the foreground, while Task A is in the background, waiting to be resumed.