android studio button usage
//this for xml file <Button android:id="@+id/button" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_centerHorizontal="true" android:layout_marginTop="109dp" android:text="hello" /> //this for java file Button btn; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); btn = (Button) findViewById(R.id.button); btn.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View view) { //do something } }); }