When we create any View in layout, we can use the android:onClick attribute to reference a method in the associated activity or fragment to handle the click events.

XML Layout

<Button android:id="@+id/button"
    ...
    // onClick should reference the method in your activity or fragment
    android:onClick="doSomething" />

// Note that this works with any class which is a subclass of View, not just Button
<ImageView android:id="@+id/image"
    ...
    android:onClick="doSomething" />

Activity/fragment code

In your code, create the method you named, where v will be the view that was touched, and do something for each view that calls this method.

public void doSomething(View v) {
    switch(v.getId()) {
        case R.id.button:
            // Button was clicked, do something.
            break;
        case R.id.image:
            // Image was clicked, do something else.
            break;
    }
}

If you want, you can also use different method for each View (in this case, of course, you don’t have to check for the ID).