java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.app.Activity.findViewById(int)' on a null object reference

Question

I always get an Error in my Android Project.

java.lang.NullPointerException: Attempt to invoke virtual method \'android.view.View android.app.Activi

Answer 1

It's very simple

public class MainActivity extends AppCompatActivity {



    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button btn1 = (Button) findViewById(R.id.button1);

        btn1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
              Intent intent = new Intent(MainActivity.this, YourNextClass.class);
                startActivity(intent);
            }
        });

    }
}