How to programmatically change button background drawable on click

1st method

1) You can create an xml in the drawable folder. This xml (you choose the name...let's call it "bg_button.xml") could look just like this:

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
   <item android:drawable="@drawable/button_02_rollover"   
  android:state_pressed="true" />                 <!-- pressed-->
  <item android:drawable="@drawable/button_02_rollover"     
 android:state_focused="true" />                   <!--focused--> 
 <item android:drawable="@drawable/button_02_normal" />  <!-- normal -->
</selector>

2) Then add button in "activity_main.xml" file in the layout folder, could look just like this:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
   xmlns:app="http://schemas.android.com/apk/res-auto" 
   xmlns:tools="http://schemas.android.com/tools"   
 android:layout_width="match_parent"   
 android:background="#e8e8e8"   
 android:layout_height="match_parent">
<Button
  android:layout_width="wrap_content"    
  android:layout_height="wrap_content"  
  android:text="Click here"  
  android:background="@drawable/bg_button" />
</RelativeLayout>

Here is an image samples that you can put in your "drawable" folder (attention: not in "drawable-v24" folder, because andorid 6.0 and 4.4 doesn't work sometime with images in this folder! ).

button_02_normal.png



button_02_rollover.png





When you run the app it looks like this:

2nd method - you can set programmatically

1) Go to "MainActivity.java" file in your java folder.

public class MainActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    final Button b = (Button) findViewById(R.id.button);
    b.setOnTouchListener(new View.OnTouchListener() {
    @Override 
    public boolean onTouch(View view, MotionEvent motionEvent) {
        switch (motionEvent.getAction()) {
            case MotionEvent.ACTION_DOWN:
                b.setBackgroundResource(R.drawable.button_02_rollover); 
               break;      
              case MotionEvent.ACTION_MOVE:
                b.setBackgroundResource(R.drawable.button_02_rollover);  
              break;           
            case MotionEvent.ACTION_UP:
                // Action up
                b.setBackgroundResource(R.drawable.button_02_normal);                         
                return true;         
          default:
                // Handle default case.          
      break;       
      }
        return false;  
  }
});

}
}

2) Then add this line android:id="@+id/button" inside the button in "activity_main.xml" file in the layout folder, could look just like this:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
   xmlns:app="http://schemas.android.com/apk/res-auto" 
   xmlns:tools="http://schemas.android.com/tools"   
 android:layout_width="match_parent"   
 android:background="#e8e8e8"   
 android:layout_height="match_parent">
<Button
    android:id="@+id/button"
    android:layout_width="wrap_content"    
  android:layout_height="wrap_content"  
  android:text="Click here"  
  android:background="@drawable/bg_button" />
</RelativeLayout>

You will have the same result