Android ExpandableListView using animation

Question

I'm using

<ExpandableListView
     android:id="@+id/listView"
     android:layout_width="match_parent"
     android:layout_height="match_parent" >
</ExpandableListView>

i want add animation slide for child when onclick parent . So How can i do ?

Answer 1

Final Update

It's been quite a while since I wrote this answer. Since then a lot has changed. The biggest change is with the introduction of RecyclerView that makes animating a list or grid easy. I highly recommend switching over to RecyclerViews if you can. For those who can't I will see what I can do regarding fixing the bugs for my library.

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Original answer

I actually do not like the popular implementation of an animated ExpandableListView that simply uses a ListView with an expand animation because in my use case, each of my groups had a lot of children, therefore it was not feasible to use a normal ListView as the child views will not be recycled and the memory usage will be huge with poor performance. Instead, I went with a much more difficult but more scalable and flexible approach.

I extended the ExpandableListView class and overrode the onCollapse and onExpand functions, I also created a subclass of a BaseExpandableListAdapter called AnimatedExpandableListAdapter. Inside the adapter, I overrode the getChildView function and made the function final so that the function cannot be overrode again. Instead I provided another function called getRealChildView for subclasses to override to provide a real child view. I then added an animation flag to the class and made getChildView return a dummy view if the animation flag was set and the real view if the flag was not set. Now with the stage set I do the following for onExpand:

1. Set the animation flag in the adapter and tell the adapter which group is expanding.
2. Call notifyDataSetChanged() (forces the adapter to call getChildView() for all views on screen).
3. The adapter (in animation mode) will then create a dummy view for the expanding group that has initial height 0. The adapter will then get the real child views and pass these views to the dummy view.
4. The dummy view will then start to draw the real child views within it's own onDraw() function.
5. The adapter will kick off an animation loop that will expand the dummy view until it is of the right size. It will also set an animation listener so that it can clear the animation flag once the animation completes and will call notifyDataSetChanged() as well.

Finally with all of this done, I was able to not only get the desired animation effect but also the desired performance as this method will work with group with over 100 children.

For the collapsing animation, a little more work needs to be done to get this all setup and running. In particular, when you override onCollapse, you do not want to call the parent's function as it will collapse the group immediately leaving you no chance to play an animation. Instead you want to call super.onCollapse at the end of the collapse animation.

UPDATE:

I spent some time this weekend to rewrite my implementation of this AnimatedExpandableListView and I'm releasing the source with an example usage here: https://github.com/idunnololz/AnimatedExpandableListView/