Android: Which Method performs the "onClick" Events of the Buttons, which are defined in the XML Layouts.

Question

I'm trying to get a better understanding of the Android framework and therefore I've created a simple App, which actually consists of just one Button. Whenever this button gets clicked, a method called sendMessage in the MainActivity starts a new activity DisplayMessageActivity, which displays a random string.

My question now is, how does the onClick Event of a button (defined in the XML layout) work in particular?! I do understand, that whenever I click my button, the method, which i defined (android:onClick="sendMessage") gets called, but I'm really curious which method calls my method in the end, because there is obviously no call of my method in the syntax.

I've already decompiled my APK File to smalicode using androguard and searched for invokes of my sendMessage method. Unfortunatly i couldnt find anything.

Can anyone explain me how this mechanism functions, because according to this post:

How exactly does the android:onClick XML attribute differ from setOnClickListener?

there should actually be a method, which calls my onClick method in the end.

Answer 1

It's done by reflection.

If you want to know exactly who is calling your method, throw an Exception and have a look at the stack trace.