Add option to keep state between sheet displays

Due to the asynchronous handling when dismissing/showing the view it is impossible to have listeners set after re-showing.

First time:

• add state change listener
• show view -> listener gets called

Second time:

• add listener
• show view (it is already showing) -> calls dismiss and returns
• gets dismissed -> removes all listeners (including new ones)
• runnable shows view again -> no listeners

Adding the listeners after calling show also doesn't work (because the runnable to show again is asynchronously called from the dismiss animation callback)

My idea would be to store a local copy of the listeners in the dismiss method and clean the global fields. Then from the animation listener:

• When it wasn't cancelled call the local listeners.
• If it was cancelled put the local listeners back into the global fields. (To remain the state before the dismiss)