Question

I create a button from layout and it works fine(display on screen when I test). When I add the click event for this Button, I always receive a NullPointerException (you can see in the below code):

   Button b1;
   int REQUEST_CODE =1;

   @Override
   public void onCreate(Bundle savedInstanceState){
    super.onCreate(savedInstanceState);

        b1 = (Button) findViewById(R.id.web_button);        
        b1.setOnClickListener(new OnClickListener() { //ERROR THIS LINE

            public void onClick(View arg0){}
        }); 
        setContentView(R.layout.intent);
   }

Answer 1

You are searching for the Button before you set the content view. You’ll have to do this:

 @Override
        public void onCreate(Bundle savedInstanceState){
            super.onCreate(savedInstanceState);

            setContentView(R.layout.intent);
            b1 = (Button) findViewById(R.id.web_button);        
            b1.setOnClickListener(new OnClickListener() { //ERROR THIS LINE
                public void onClick(View arg0){
                }
            }); 


        }