Question

Let’s say I have a method like this into my activity, and set it as onClick field of different buttons into xml:

public void onButtonPressedFromView(View button) {
   switch(button.getId()) {
   case (R.id.button1) :
      //do something
      break;
   case (R.id.button2) :
      //do something different
      break;
   default :
      //default action
      break;
   }
}

It comes out that, if I press for instance button1, the id obtained with button.getId() is always bigger of 1 than the id obtained with R.id.button1. It’s quite easy to solve, I just changed my code into

switch(button.getId() - 1)

but I don’t like it, and would like to understand the difference between these two ways of obtaining the id of a view.

Answer 1

You should be comparing known buttons to the presses.

onCreate(...) {
    ...
   Button myButton1 = (Button)findViewById(R.id.somebutton);
   Button myButton2 =....
}



public void onButtonPressedFromView(View button) {
   switch(button.getId()) {
   case (myButton1.getId()) :
      //do something
      break;
   case (myButton2.getId()) :
      //do something different
      break;
   default :
      //default action
      break;
   }
}

It is important to not assume myButton == button. For instance, if you use a button in a ListView it will likely have several instances and can thus only be comparable by the getId() property.