onDismissalStarted

This should be called, before the dismissal of the panel containing this is started.

There are known issues with the dismissal animations. For example, fading animations are not supported and there may be performance issues with translation animations. As a workaround for these problems, if ttHideContentOnDismissalStarted is set, the activity is hidden and the background is shown.

Note: This method does not get called automatically. Use callOnDismissalStartedForChildActivityViews to call this method for all child views of a ViewGroup.