android studio button usage

1//this for xml file 
2<Button  
3        android:id="@+id/button"  
4        android:layout_width="wrap_content"  
5        android:layout_height="wrap_content"  
6        android:layout_centerHorizontal="true"  
7        android:layout_marginTop="109dp"  
8        android:text="hello"  
9 /> 
10
11//this for java file 
12Button btn;
13  @Override  
14    protected void onCreate(Bundle savedInstanceState) {  
15        super.onCreate(savedInstanceState);  
16        setContentView(R.layout.activity_main);  
17  btn = (Button) findViewById(R.id.button);
18        btn.setOnClickListener(new View.OnClickListener() {  
19            @Override  
20            public void onClick(View view) {  
21               //do something
22            }  
23        }); 
24    } 

1Button b = findById();

1mycodes_Button.setOnTouchListener(new OnTouchListener() {
2    @Override
3    public boolean onTouch(View v, MotionEvent event) {
4        mycodes_Button.setPressed(true);
5        return true;
6    }
7});
8