Animation for expandableListView

问题:

Is it possible to apply an expand or collapse animation for expandableListView?

回答1:

It can be done using a simple ListView that contains an initially hidden view and a custom class that extends Animation. The basic idea is to start with View.GONE then gradually re-size the margin from a negative value to the required size while setting visibility to View.VISIBLE.

See:

• https://github.com/tjerkw/Android-SlideExpandableListView
• Android Animation: Hide/Show Menu
• How do I animate View.setVisibility(GONE)

..and finally

• Cool toolbar for ListView items + source

The last example contains all the code you need. It looks a bit hackish to me, especially the fact that you must initially set view.bottomMargin = -50 or more, otherwise the animation does not work properly the first time, but so far I did not find any viable alternative (apart from using a ScrollView with your own container items instead of a ListView).

And finally, this app includes the above example, among lots of other useful examples with links to sources:

• https://market.android.com/details?id=com.groidify.uipatterns

Update: Google removed the app from play store allegedly for intellectual property violation (although it only contained demos and links to open source projects), the author now made the apk available for direct download from http://goo.gl/ihcgs For more details see https://plus.google.com/108176685096570584154/posts. NB: I'm not affiliated with the author.

回答2:

I have done a similar job for a simple list view.For doing that I overrode the getView method and applied translate up( or down) animation on each list item.The degree of translation was decided by the position of the list item.

回答3:

I've found a possible (partial) workaround for this problem.

first you need to store the scroll state of the ExpnadableListView :

@Override
public void onScrollStateChanged(final AbsListView view, final int scrollState) {
    this.mScrollState = scrollState;
}

public int getScrollState() {
    return this.mScrollState;
}

for the listView itself, you need to store which group was clicked, so that only its children will get animated:

mListView.setOnGroupClickListener(...
@Override
public boolean onGroupClick(...){
mGroupPosition=groupPosition;

now, in the getChildView() method, you check the state of the scrolling , and if it's idle, you start the animation, for example:

public View getChildView(...) {
// <=prepare rootView and return it later
if (groupPosition==mGroupPosition&&getScrollState() == OnScrollListener.SCROLL_STATE_IDLE)
    rootView.setAnimation(...)

this will set an animation for the child views each time you expand the group.

the drawback of this are:

1. only for the expanded child views. you will need to think of extra logic to animate them when collapsing the group.
2. all animations start at once . you will need to add multiple animations one after another if you wish that it would work otherwise.