在 API 22 上启动 AnimatedVectorDrawable 时出现 NullPointerException

Question

I'm using this snippet to start an AnimatedVectorDrawable animation:

AnimatedVectorDrawable vectorAnim = (AnimatedVectorDrawable) ((ImageView) child).getDrawable();
vectorAnim.start();

(Basically I get the android:src of the ImageView, which is an AnimatedVectorDrawable , and then I launch the animation).

It works fine on every device I tested until now, but when I run my app on an API 22 device I get this error:

java.lang.NullPointerException: Attempt to invoke virtual method 'int java.util.ArrayList.size()' on a null object reference
                                                                          at android.graphics.drawable.AnimatedVectorDrawable.isStarted(AnimatedVectorDrawable.java:427)
                                                                          at android.graphics.drawable.AnimatedVectorDrawable.start(AnimatedVectorDrawable.java:440)
                                                                          at com.brickx.creartup.MainRoadmapAdapter.animateViews(MainRoadmapAdapter.java:263)
                                                                          at com.brickx.creartup.MainRoadmapAdapter.access$100(MainRoadmapAdapter.java:31)
                                                                          at com.brickx.creartup.MainRoadmapAdapter$1.onInflate(MainRoadmapAdapter.java:66)
                                                                          at android.view.ViewStub.inflate(ViewStub.java:284)
                                                                          at com.brickx.creartup.MainRoadmapAdapter.inflateBackground(MainRoadmapAdapter.java:215)
                                                                          at com.brickx.creartup.MainRoadmapAdapter.onCreateViewHolder(MainRoadmapAdapter.java:71)
                                                                          at com.brickx.creartup.MainRoadmapAdapter.onCreateViewHolder(MainRoadmapAdapter.java:31)
                                                                          at android.support.v7.widget.RecyclerView$Adapter.createViewHolder(RecyclerView.java:6519)
                                                                          at android.support.v7.widget.RecyclerView$Recycler.tryGetViewHolderForPositionByDeadline(RecyclerView.java:5706)
                                                                          at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:5589)
                                                                          at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:5585)
                                                                          at android.support.v7.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:2231)
                                                                          at android.support.v7.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1558)
                                                                          at android.support.v7.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1518)
                                                                          at android.support.v7.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:610)
                                                                          at android.support.v7.widget.RecyclerView.dispatchLayoutStep2(RecyclerView.java:3719)
                                                                          at android.support.v7.widget.RecyclerView.dispatchLayout(RecyclerView.java:3436)
                                                                          at android.support.v7.widget.RecyclerView.onLayout(RecyclerView.java:3988)
                                                                          at android.view.View.layout(View.java:15671)
                                                                          at android.view.ViewGroup.layout(ViewGroup.java:5038)
                                                                          at android.support.v4.widget.SwipeRefreshLayout.onLayout(SwipeRefreshLayout.java:611)
                                                                          at android.view.View.layout(View.java:15671)
                                                                          at android.view.ViewGroup.layout(ViewGroup.java:5038)
                                                                          at android.widget.RelativeLayout.onLayout(RelativeLayout.java:1076)
                                                                          at android.view.View.layout(View.java:15671)
                                                                          at android.view.ViewGroup.layout(ViewGroup.java:5038)
                                                                          at android.widget.FrameLayout.layoutChildren(FrameLayout.java:579)
                                                                          at android.widget.FrameLayout.onLayout(FrameLayout.java:514)
                                                                          at android.view.View.layout(View.java:15671)
                                                                          at android.view.ViewGroup.layout(ViewGroup.java:5038)
                                                                          at android.support.constraint.ConstraintLayout.onLayout(ConstraintLayout.java:1197)
                                                                          at android.view.View.layout(View.java:15671)
                                                                          at android.view.ViewGroup.layout(ViewGroup.java:5038)
                                                                          at android.support.design.widget.HeaderScrollingViewBehavior.layoutChild(HeaderScrollingViewBehavior.java:132)
                                                                          at android.support.design.widget.ViewOffsetBehavior.onLayoutChild(ViewOffsetBehavior.java:42)
                                                                          at android.support.design.widget.AppBarLayout$ScrollingViewBehavior.onLayoutChild(AppBarLayout.java:1361)
                                                                          at android.support.design.widget.CoordinatorLayout.onLayout(CoordinatorLayout.java:874)
                                                                          at android.view.View.layout(View.java:15671)
                                                                          at android.view.ViewGroup.layout(ViewGroup.java:5038)
                                                                          at android.support.v4.widget.DrawerLayout.onLayout(DrawerLayout.java:1172)
                                                                          at android.view.View.layout(View.java:15671)
                                                                          at android.view.ViewGroup.layout(ViewGroup.java:5038)
                                                                          at android.widget.FrameLayout.layoutChildren(FrameLayout.java:579)
                                                                          at android.widget.FrameLayout.onLayout(FrameLayout.java:514)
                                                                          at android.view.View.layout(View.java:15671)
                                                                          at android.view.ViewGroup.layout(ViewGroup.java:5038)
                                                                          at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1703)
                                                                          at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1557)
                                                                          at android.widget.LinearLayout.onLayout(LinearLayout.java:1466)
                                                                          at android.view.View.layout(View.java:15671)

Any idea on what is going on here?

EDIT

I know what NullPointerException means, but sadly I think I have no control over this one. And I can't figure out why this exception is being thrown here...

Answer 1

OK, I figured out the root of the problem! Even if I have no idea how to solve this issue properly.

The crash happens when I try to launch the animation on an AnimatedVectorDrawable which has NO target attribute (I'm using a single XML file to define the vector drawable and its animations).

More precisely, I think android looks into the animated-vector element and throws an error if no target if found. Again, I only encountered this issue on API 22 so far, but I haven't tested other APIs yet...

I can only think of two solutions for now:

• either add at least one target element into the AnimatedVectorDrawable ,
• or use a simple VectorDrawable if no animation is needed (I used AnimatedVectorDrawable regardless whether or not my vector was animated, to be able to easily add animations to it later if I wanted to).

EDIT

I found a simple workaround to avoid changing everything, that maybe can help others: I just had to add a dumb target to all my AnimatedVectorDrawable that shouldn't be animated.

<target android:name="vector">
    <aapt:attr name="android:animation">
        <objectAnimator
            android:propertyName="alpha"
            android:valueTo="1"/>
    </aapt:attr>
</target>

That way nothing changes in the AnimatedVectorDrawable , but the error is not showing. I don't recommend this though, as it's pretty dirty and can lead to other issues.

Answer 2

Found the same issue on API 21 and 22.

The solution that helped me was to define both parameters android:valueFrom and android:valueTo on objectAnimator in xml :

<objectAnimator
    android:propertyName="fillColor"
    android:duration="250"
    android:valueFrom="#393749"
    android:valueTo="#00000000"
    android:valueType="colorType"/>

But on API above it's working without android:valueFrom (crazy droid does not save our time:)