Why I get Null Pointer Exception in Android

Question

I am facing issue of NullPointerException. In my app I have two classes MainActivity and Test. I am creating object main of MainActivity inside Test class. When I call display method of MainActivity inside Test class main.display(); I get the NullPointerException. Please check my sample code below and recommend me changes where I am doing wrong.

public class MainActivity extends Activity {


    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        requestWindowFeature(Window.FEATURE_NO_TITLE);
        setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT); // Fixed
        getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON); // orientation

        setContentView(R.layout.training_ten_position);

        Test test = new Test(10);

    }


    public  MainActivity()  {
        super();
    }
    public void display() {

    }


    }



public class Test {
        .
        .
        .
        MainActivity main;

        public Test(int duration) {
            // Initializing data member
            main = new MainActivity();
        }

        public void delay() {
            .
            .
            .
            main.display();
        }

you should not create an instance of main activity. activity is started by startActivity — Raghunandan
– Raghunandan, Commented Aug 26, 2013 at 9:44

Biraj Zalavadia · Accepted Answer · 2013-08-26 09:49:46Z

1

Do like this

do nor create instance of MainActivity class.

public class MainActivity extends Activity{

 //Make Your Function static 

  public static void display(){
    //Do your code 
    // whatever variables or views you want to use in this method make them static
  }

}

public class Test extend Activity{
   //how call display function
   MainActivity.display();

}

answered Aug 26, 2013 at 9:49

Biraj Zalavadia

28.5k10 gold badges63 silver badges77 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Why I get Null Pointer Exception in Android

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related