Button variable turns to null after calling method

Question

In my mainactivity I have the following snip

MainActivity.class

private Button btnx10;

@Override
protected void onCreate(Bundle savedInstanceState) {
         


        

Answer 1

Since you have declared the Button in Scope of Method onCreate()

Button btnx10=(Button)findViewById(R.id.MainCOPbtn);

and you are trying to access it outside of the method onCreate(), that makes it inaccessible outside of this method.

Just make the reference on class level (Globally) and use the same Reference in onCreate() method.

you can do this:-

private Button btnx10;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    btnx10 = (Button)findViewById(R.id.MainCOPbtn);
    DrawLines();
}


private void drawLines(){
   float centerYOnImage1 = btnx10.getHeight()/2;
}