android: using ActivityGroup to embed activities

Question

Im in the conceptualizing/design phase of building an app and i've hit a bit of a snag. Essentially i was looking for a way to embed one activity into the UI of another similar to how a TabHost/TabActivity. There would be a window at the top of the screen which would contain the other activity, and below that would be buttons and controls that are independent of the above activity and should always be visible. The user would be able to navigate from one activity to another in the window without causing any change to the below controls.

While looking into the issue i ran across ActivityGroup, which looked like it would be useful, but how would i implement it? Anyone have experience with ActivityGroup or have another idea?

Solution

Yes, you'd implement an ActivityGroup, which will be the container of your other Activities. When the user clicks one of the buttons, you'd get a reference to the LocalActivityManager, and use it to start, and embed the inner activity. Something like this:

LocalActivityManager mgr = getLocalActivityManager();

Intent i = new Intent(this, SomeActivity.class);

Window w = mgr.startActivity("unique_per_activity_string", i);
View wd = w != null ? w.getDecorView() : null;

if(wd != null) {
    mSomeContainer.addView(wd);
}

Note, using this method can be pretty complicated, because unless the focus is just right, pressing the hardware buttons (like the menu button) will only only trigger events on the ActivityGroup instead of the inner Activity. You have to find some way to focus the inner activity after you add it to the container view, at which point the even will happen in the inner activity and propagate to the container activity.

It can be done, I've done it... and it works. It's just a bit more complicated than I think it should be.

Anyway, I got most of this information by looking at the TabHost code, which can be found here