How to erase Activity stack in Android?

I'm building a pizza order app. When the user adds an item to his cart, he is given an option to go to the item categories and browse/add new items. What I want to do is:

Main Screen > CategoryList(first appearance) > Pizzas in that category > Pizza Details > Shopping Cart > CategoryList(second apperance)..

I need to erase the Activity stack so that after adding an item to the cart, if the user touches the back button, he/she should go back to CategoryList(first appearance). "Pizzas in that category > Pizza Details > Shopping Cart" must be erased. If he/she touches back again, he/she should be at Main Screen.

How can I accomplish this?

Solution

You could try to push the latest activity using intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
or
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

see
http://developer.android.com/reference/android/content/Intent.html#FLAG_ACTIVITY_CLEAR_TOP

So then you clear the stack of activities under your new activity.

Additionally you could try to override the back-event:

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
    if (keyCode == KeyEvent.KEYCODE_BACK) {
        moveTaskToBack(true);
        return true;
    }
    return super.onKeyDown(keyCode, event);
}