[android] displaying a string on the textview when clicking a button in android

Just check your code in .java class

You had written below line

 mybtn.setOnClickListener(this);

before initializing the mybtn object I mean

mybtn = (Button)findViewById(R.id.mybtn);

just switch this two line or put that line "mybtn.setOnClickListener(this)" after initializing your mybtn object and you will get the answer what you want..