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我正在玩 MotionLayout 并遇到了一个奇怪的问题

当我将使用的库版本从更改com.android.support.constraint:constraint-layout:2.0.0-alpha2为com.android.support.constraint:constraint-layout:2.0.0-alpha3

我的应用程序崩溃了：

E/AndroidRuntime: FATAL EXCEPTION: main
Process: ru.sergik.collapsibleexoplayer, PID: 1376
java.lang.NullPointerException: Attempt to invoke virtual method 'int androidx.constraintlayout.motion.widget.MotionScene.getDuration()' on a null object reference
    at androidx.constraintlayout.motion.widget.MotionLayout.dispatchDraw(MotionLayout.java:1634)
    at android.view.View.updateDisplayListIfDirty(View.java:19306)
    at android.view.View.draw(View.java:20093)
    at android.view.ViewGroup.drawChild(ViewGroup.java:4421)
    at android.view.ViewGroup.dispatchDraw(ViewGroup.java:4207)
    at androidx.constraintlayout.widget.ConstraintLayout.dispatchDraw(ConstraintLayout.java:2072)
    at android.view.View.updateDisplayListIfDirty(View.java:19306)
    at android.view.View.draw(View.java:20093)
    at android.view.ViewGroup.drawChild(ViewGroup.java:4421)
    at android.view.ViewGroup.dispatchDraw(ViewGroup.java:4207)
    at android.view.View.updateDisplayListIfDirty(View.java:19306)
    at android.view.View.draw(View.java:20093)
    at android.view.ViewGroup.drawChild(ViewGroup.java:4421)
    at android.view.ViewGroup.dispatchDraw(ViewGroup.java:4207)
    at android.view.View.updateDisplayListIfDirty(View.java:19306)
    at android.view.View.draw(View.java:20093)
    at android.view.ViewGroup.drawChild(ViewGroup.java:4421)
    at android.view.ViewGroup.dispatchDraw(ViewGroup.java:4207)
    at android.view.View.updateDisplayListIfDirty(View.java:19306)
    at android.view.View.draw(View.java:20093)
    at android.view.ViewGroup.drawChild(ViewGroup.java:4421)
    at android.view.ViewGroup.dispatchDraw(ViewGroup.java:4207)
    at android.view.View.updateDisplayListIfDirty(View.java:19306)
    at android.view.View.draw(View.java:20093)
    at android.view.ViewGroup.drawChild(ViewGroup.java:4421)
    at android.view.ViewGroup.dispatchDraw(ViewGroup.java:4207)
    at android.view.View.draw(View.java:20373)
    at com.android.internal.policy.DecorView.draw(DecorView.java:980)
    at android.view.View.updateDisplayListIfDirty(View.java:19315)
    at android.view.ThreadedRenderer.updateViewTreeDisplayList(ThreadedRenderer.java:686)
    at android.view.ThreadedRenderer.updateRootDisplayList(ThreadedRenderer.java:692)
    at android.view.ThreadedRenderer.draw(ThreadedRenderer.java:800)
    at android.view.ViewRootImpl.draw(ViewRootImpl.java:3496)
    at android.view.ViewRootImpl.performDraw(ViewRootImpl.java:3283)
    at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2818)
    at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1780)
    at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:7827)
    at android.view.Choreographer$CallbackRecord.run(Choreographer.java:911)
    at android.view.Choreographer.doCallbacks(Choreographer.java:723)
    at android.view.Choreographer.doFrame(Choreographer.java:658)
    at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:897)
    at android.os.Handler.handleCallback(Handler.java:789)
    at android.os.Handler.dispatchMessage(Handler.java:98)
    at android.os.Looper.loop(Looper.java:164)
    at android.app.ActivityThread.main(ActivityThread.java:6944)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:327)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1374)

进行一些调试时，我发现 MotionLayout 的版本存在一些差异，导致此崩溃：

MotionLayout alpha-3

MotionLayout alpha-2

正如您在 alpha-3 中看到的，this.mDevModeDraw.draw(canvas, this.mFrameArrayList, this.mScene.getDuration(), this.mDebugPath);在尝试获取运动场景持续时间时将被调用并导致崩溃this.mScene.getDuration()，但在 alpha-2 中，由于 if 条件不同，它不会被调用。

我应该如何解决这个问题？

4

4 回答 4

3

app:layoutDescription尽管您可以检查您是否在布局集中具有该属性，但您尚未发布您的 XML 。

于 2019-03-14T11:08:50.073 回答
2

对我来说，它发生在我用标签MotionLayout对其内容进行子类化和膨胀时。<merge...忘记了合并标签的参数被忽略，您必须手动将它们应用回代码中。

所以它现在看起来像这样：

class SomeLayout : MotionLayout {

constructor(context: Context, attrs: AttributeSet?, defStyleAttr: Int) : super(context, attrs, defStyleAttr) {
    inflate(context, R.layout.some_layout, this)
    loadLayoutDescription(R.xml.some_motion_scene)
    setTransition(R.id.start, R.id.end)
}

...
于 2019-02-06T14:48:33.893 回答
1

通过从更新库修复了相同的问题

implementation 'androidx.constraintlayout:constraintlayout:2.0.1'

至

implementation 'androidx.constraintlayout:constraintlayout:2.0.4'
于 2020-11-20T10:30:46.750 回答
0

这次特定崩溃的根本原因是 AAPT 中的更改发现了 ConstraintLayout 的新属性中的错误。这已在其中一个测试版中得到修复，因此如果您现在进入 MotionLayout，您应该只使用最新的稳定版本。如果由于某种原因您卡在旧的 alpha 版本上，您可以将它们放入您的values/attrs.xml文件中以解决崩溃问题：

    <attr name="duration"/>
    <attr name="flow_horizontalSeparator"/>
    <attr name="flow_verticalSeparator"/>
    <attr name="motionPathRotate"/>
    <attr name="motionProgress"/>
    <attr name="waveDecay"/>

我强烈建议改用最新的稳定版本 2.0.4。

于 2020-12-29T06:50:13.397 回答