Adding Custom ImageButton to layout in Android causes error

Question

I will start by saying this, while I have some Java training, is my first foray into development for Android.

What I have done is created a custom ImageButton called MapCell that is basically an ImageButton that holds a few extra pieces of information, and it compiles fine.

My problem comes when I want to procedurally create a MapCell in the relevant Activity and add it to my TableLayout which is defined in the xml and has the id 'mapTable'. The relevant bit looks like this:

Random randy = new Random();

MapCell n = new MapCell(randy.nextInt(4), this); //the random number is part of my extra info

findViewById(R.id.mapTable).addView((View)n, 20, 20); //add cell to display

I get one error out of that: The method addView(View, int, int) is undefined for the type View

Which to me sounds like utter nonsense. I put that View cast in there as desperation after I got this same error with n sitting by itself and nothing changed (Obviously my MapCell is already a View since it extends ImageButton).

I hope a new pair of eyes can tell me what this is about, since I've checked for similar problems and I didn't find any quite like this. Let me now if you need to see more code.

Answer 1

The method findViewById returns a View and the View class doesn't have the method addView(this method is implemented in the ViewGroup and its subclasses). Instead you should write:

((TableLayout)findViewById(R.id.mapTable)).addView(n, 20, 20);

I've cast the return of the findViewById method in a class that actually has the addView method.

Answer 2

You got this problem because method findViewById(R.id.mapTable) returns View object. In android you can't add one View to another.

You can use addView function with ViewGroup, and all LinearLayout (etc.) objects.