Can't find TextView in another View

Question

I can't find the mistake. I want to set the text of a textview. But when I'm setting the text I get an error message (see below for this). What I'm doing wrong? A little further down I call a button. This call works perfectly. What am I doing wrong when I call up the text view and set the text of this?

private void popUp(int layout, int button) {
    epicDialog.setContentView(layout);
    epicDialog.getWindow().setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));

    TextView test = (TextView) epicDialog.findViewById(R.id.textView_popup);
    test.setText("Hello");

    ....
   Button button;
    button= epicDialog.findViewById(R.id.button);
    button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            // do something
        }

    });        
}

the error

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference

Answer 1

you forgot to show the dialog before finding the textview.

 private void popUp(int layout, int button) {
        epicDialog.setContentView(layout);
        epicDialog.getWindow().setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));
        epicDialog.show();

        TextView test = (TextView) epicDialog.findViewById(R.id.textView_popup);
        test.setText("Hello");

        ....
       Button button;
        button= epicDialog.findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // do something
            }

        });        
    }

Answer 2

I think you add wrong id in java code. check your xml.

android:id="@+id/textView"