Question

I have an activity that contains a custom view and several buttons.

Now, if the view is clicked, I’m handling it in the view class with an overwriten onTouchEvent.

However, depending on where the user clicked exactly, I might want to change the text contained in the buttons in the parent activity.

In other words: How do I make the parent activity receive data from my custom view?

Answer 1

Define an interface and use a callback to let the activity know that the view has been touched.

public Interface ViewWasTouchedListener {
    void onViewTouched(float x, float y);
}

In your custom view

ArrayList<ViewWasTouchedListener> listeners = new ArrayList<ViewWasTouchedListener>();

...

public void setWasTouchedListener(ViewWasTouchedListener listener){
    listeners.add(listener);
}

In your touch event

for (ViewWasTouchedListener listener:listeners){
   listener.onViewTouched(x,y);
}

In your Activity:

public class Test extends Activity implements ViewWasTouchedListener {

...

@Override
public void onCreate(Bundle savedInstanceState) 
{
    ...
    MyExtendedView customView = (MyExtendedView)findViewById(R.id.myCustomeView);
    customView.setWasTouchedListener(this);
    ...
}

public void onViewTouched(float x, float y){
   // do whatever you need to do
}

You could improve the view class by adding removeViewWasTouchedListener and checking that you do not add the same listener twice in setViewWasTouchedListener.