Does Android keep the view object hierarchy in memory?

Question

When I create a button:

@Override
public void onCreate(Bundle savedInstanceState)
{
   super.onCreate(savedInstanceState);
   setContentView(R.layout.main);

   LinearLayout layout = …;

   Button btn = new Button(this);
   btn.setText("My Button");

   layout.addView(btn);
}

If I don't keep a strong reference to the btn , does Android keep the btn instance alive?

For example, does layout.getChildView(0) return the exact instance ( btn )? or does Android create and return a new instance of Button and return it?

I'm not talking about subclassing, (eg class MyButton extends Button ) which I think it's obvious it must be kept in memory, I am only asking about built-in view classes.

Answer 1

ViewGroup stores strong references on its children in an array. If you take a look into ViewGroup sources you find following field:

private View[] mChildren;

And when you call getChildAt you get an instance from this array:

public View getChildAt(int index) {
    if (index < 0 || index >= mChildrenCount) {
        return null;
    }
    return mChildren[index];
}

Answer 2

对于任何视图组，当您一次添加任何子视图时，它不会创建新实例。