Question

I am trying to develop a screen consisting of buttons where clicking a button launches a custom dialog. The dialog has a ok button that closes it. I wrote the following code for it but is giving me a NullPointerException :

Dialog modalDialog;
@Override
public void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    setContentView(R.layout.input);

    Button modal = (Button)findViewById(R.id.ModalityButton);

    modal.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            modalDialog = new Dialog(Input.this);
            modalDialog.setContentView(R.layout.modality);
            modalDialog.setCancelable(true);
            Button ok = (Button) findViewById(R.id.modality_ok);

            ok.setOnClickListener(new OnClickListener() { // shows null pointer error at this line
                @Override
                public void onClick(View v) {
                    modalDialog.cancel();
                }
            });

            modalDialog.show();
        }
    });
}

Answer 1

Search for the button ok in the dialog’s layout:

Button ok = (Button) modalDialog.findViewById(R.id.modality_ok);