Question

I am developing an android app which tracks touch events for the whole application. For that purpose, I want to override onTouchEvent() without an activity; i.e., inside a simple Java class, I don’t whether it’s possible. Any ideas are welcome.

Answer 1

No, you cannot arbitrarily override onTouchEvent, particularly in a “simple Java class”, i.e. one that does not extend a View.

Solution 1

If you want to capture all touches to your app, override onInterceptTouchEvent() in your main layout. So, if your main layout is a LinearLayout, do something like:

public class MyTouchLayout extends LinearLayout {
    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        // Do whatever with your touch event
        return false; // Do not prevent the rest of the layout from being touched
    }
}

Then, in your XML, you’d use:

<com.example.MyTouchLayout
    ...
    >

    <!-- The rest of your layout -->

</com.example.MyTouchLayout>

Solution 2

This is by far the simpler solution, though I’ve had varying luck with it in the past and would never suggest that you reply upon it.

You can simply get the View that contains all your content (the root View, a LinearLayout above), then give it a listener.

View v = findViewById(android.R.id.content); // Find the root View; you may have to give it your own ID in the XML, and use that
v.setOnTouchListener(new OnTouchListener {
    // ...
}