1. Use internal anonymous class:

Private Button Button; 
 @Override 
 Protected void onCreate (Bundle Savedinstancestate) { 
 Super.Oncreate (Savedinstancestate); 
 setContentView (r.Layout.activity_main); 
 Button = (Button) FindViewByid (R.id.button); 
 Button.SetonClickListener (New Onclicklistener () { 
 @Override 
 public void onClick (view v) { 
 // Add logic here 
 } 
 }); 
 }

2. Realize the interface to register the monitor

PUBLIC Class MainAICTIVITITY Extends Activity Implements View.onClickListener { 
   Private Button Button; 
     @Override 
     Protected void onCreate (Bundle Savedinstancestate) { 
         Super.Oncreate (Savedinstancestate); 
         RequestWindow Feature (Window. Feature_no_title); 
         setContentView (r.Layout.activity_main); 
         Button = (Button) FindViewByid (R.id.button); 
         Button.SetonClickListener (this); 
     } 

     @Override 
     public void onClick (view v) { 
     switch (v.getid ()) {{ 
         case r.id.button: { 
             Toast.makeText (mainactivity.this, "Monitoring by implementing interface", toast.length_short) .show ();););); 
         } Break; 
         default: break; 
     } 
     } 
 }