Page callbacks

ExpandablePageLayout offers multiple ways of receiving callbacks for observing changes to the its movement.

State changes

There are four different states:

• PageState.COLLAPSING
• PageState.COLLAPSED
• PageState.EXPANDING
• PageState.EXPANDED

These can be accessed using ExpandablePage.currentState or by registering callbacks,

expandablePage.addStateChangeCallbacks(object: SimplePageStateChangeCallbacks() {

  override fun onPageAboutToExpand(expandAnimDuration: Long) {}

  override fun onPageExpanded() {}

  override fun onPageAboutToCollapse(collapseAnimDuration: Long) {}

  override fun onPageCollapsed() {}
})

Overridable functions

ExpandablePageLayout also offers the same set of callbacks as open functions that can be overridden when subclassing it. This can also be useful for apps that use a View driven navigation stack instead of multiple Activities or Fragments.

class Screen(context: Context) : ExpandablePageLayout(context) {
  
  override fun onPageAboutToExpand(expandAnimDuration: Long) {}

  override fun onPageExpanded() {}

  override fun onPageAboutToCollapse(collapseAnimDuration: Long) {}

  override fun onPageCollapsed() {}
}

Pull-to-collapse gesture

expandablePage.addOnPullListener(object: SimpleOnPullListener() {

  override fun onPull(...) {}

  override fun onRelease(collapseEligible: Boolean) {}
})