ViewDataBinding 在 activity.finish() 之后导致崩溃恢复应用程序,NPE 在视图附件期间访问 mRebindRunnable
ViewDataBinding causes crash resuming app after activity.finish(), NPE on access to mRebindRunnable during view attachment
成功启动 activity 后崩溃表面,使用数据绑定膨胀片段。在根级别按下后退按钮后,应用程序(正确地)经过 activity.finish()
但将应用程序实例保留在后台。
重新启动后,应用程序会在创建视图后的某个时刻崩溃(至少基于调试)。
崩溃:
2020-08-26 20:00:50.626 9706-9706/com.org.app.dev E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.org.app.dev, PID: 9706
java.lang.NullPointerException: Attempt to read from field 'java.lang.Runnable androidx.databinding.ViewDataBinding.mRebindRunnable' on a null object reference
at androidx.databinding.ViewDataBinding.access0(ViewDataBinding.java:65)
at androidx.databinding.ViewDataBinding.onViewAttachedToWindow(ViewDataBinding.java:165)
at android.view.View.dispatchAttachedToWindow(View.java:19564)
at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:3437)
at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:3437)
at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:3437)
at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:3437)
at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:3437)
at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:3437)
at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:3437)
at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:3437)
at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:3437)
at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:3437)
at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:3437)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2028)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1721)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:7598)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:966)
at android.view.Choreographer.doCallbacks(Choreographer.java:790)
at android.view.Choreographer.doFrame(Choreographer.java:725)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:951)
at android.os.Handler.handleCallback(Handler.java:883)
at android.os.Handler.dispatchMessage(Handler.java:100)
at android.os.Looper.loop(Looper.java:214)
at android.app.ActivityThread.main(ActivityThread.java:7356)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
深入研究源代码、调试,我能收集到的最好信息是 ViewDataBinding 发现以前绑定的视图已重新附加,并尝试重新绑定现有资源。但是,它显然丢失了对静态可运行对象的引用。来自 ViewDataBinding 的相关源代码:
private static final OnAttachStateChangeListener ROOT_REATTACHED_LISTENER;
static {
if (VERSION.SDK_INT < VERSION_CODES.KITKAT) {
ROOT_REATTACHED_LISTENER = null;
} else {
ROOT_REATTACHED_LISTENER = new OnAttachStateChangeListener() {
@TargetApi(VERSION_CODES.KITKAT)
@Override
public void onViewAttachedToWindow(View v) {
// execute the pending bindings.
final ViewDataBinding binding = getBinding(v);
binding.mRebindRunnable.run();
v.removeOnAttachStateChangeListener(this);
}
@Override
public void onViewDetachedFromWindow(View v) {
}
};
}
}
我确实从以下位置注意到了相同的堆栈跟踪:App crash caused by data binding related to java.lang.Runnable android.databinding.ViewDataBinding.mRebindRunnable,但该问题似乎与应用程序立即崩溃有关(我的问题仅在尝试补充水分后发生)。但是从那个问题来看,我确实注意到记录我的视图标签返回空值。我尝试在 xml 中设置一个静态标签,没有任何变化。
我尝试过的其他事情:
- 如果我只实例化片段,则不会出现问题(但显然不会附加到框架布局
- 没有明确的调试崩溃点(onCreateView、onViewCreated都被调用了)
- 我试着改变我膨胀的方式,分配生命周期所有者,绑定视图模型;没有任何变化影响崩溃。
- 我尝试调用绑定(invalidateAll()、unbind())但没有成功。
同样,只有当应用程序实例仍然存在但 activity 已被销毁时,问题才会出现。感谢您的任何提示!!
编辑:相关代码位
Activity (Java) -
ExampleFragment exampleFragment = new ExampleFragment(exampleParameter);
FragmentManager fragmentManager = getSupportFragmentManager();
fragmentManager
.beginTransaction()
.add(R.id.example_frame_layout, exampleFragment, EXAMPLE_TAG)
.commit();
片段(Kotlin)-
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
binding = FragmentExampleBinding.inflate(inflater, container, false).apply {
lifecycleOwner = viewLifecycleOwner
}
return binding.root
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
binding.run {
viewModel = this@ExampleFragment.viewModel
}
}
更新
有趣的是,当我尝试将相同的片段(新实例化的)膨胀到不同的(未启动的)时,我现在看到了这一点 activity。调试这种情况,除了在膨胀并返回绑定的根视图(而不是 null)后遇到崩溃之外,我找不到任何问题。我已经尝试使用为布局创建的静态方法以及 DataBindingUtil。两者都经历了同样的崩溃。
尤里卡!!
不仅 <merge/>
不能用于 <include/>
布局(也记录在此处:https://developer.android.com/topic/libraries/data-binding/expressions#includes)
但是
绑定也不适用于根部有 <merge/>
的 <include/>
布局。这是它的样子:
<layout>
...
<include layout="id/sub_layout"
bind:viewModel="@{viewModel} />
...
</layout>
以及问题 (R.id.sub_layout.xml):
<layout>
...
<merge>
<TextView/>
<ImageView/>
</merge>
...
</layout>
奇怪的是,它似乎在启动 activity 时起作用,但很高兴知道导致此问题的症状(inflation 后异步崩溃)。
对于那些在数据绑定和错误消息方面遇到麻烦的人,我绝对建议尝试更改您的布局。
成功启动 activity 后崩溃表面,使用数据绑定膨胀片段。在根级别按下后退按钮后,应用程序(正确地)经过 activity.finish()
但将应用程序实例保留在后台。
重新启动后,应用程序会在创建视图后的某个时刻崩溃(至少基于调试)。
崩溃:
2020-08-26 20:00:50.626 9706-9706/com.org.app.dev E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.org.app.dev, PID: 9706
java.lang.NullPointerException: Attempt to read from field 'java.lang.Runnable androidx.databinding.ViewDataBinding.mRebindRunnable' on a null object reference
at androidx.databinding.ViewDataBinding.access0(ViewDataBinding.java:65)
at androidx.databinding.ViewDataBinding.onViewAttachedToWindow(ViewDataBinding.java:165)
at android.view.View.dispatchAttachedToWindow(View.java:19564)
at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:3437)
at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:3437)
at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:3437)
at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:3437)
at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:3437)
at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:3437)
at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:3437)
at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:3437)
at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:3437)
at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:3437)
at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:3437)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2028)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1721)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:7598)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:966)
at android.view.Choreographer.doCallbacks(Choreographer.java:790)
at android.view.Choreographer.doFrame(Choreographer.java:725)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:951)
at android.os.Handler.handleCallback(Handler.java:883)
at android.os.Handler.dispatchMessage(Handler.java:100)
at android.os.Looper.loop(Looper.java:214)
at android.app.ActivityThread.main(ActivityThread.java:7356)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
深入研究源代码、调试,我能收集到的最好信息是 ViewDataBinding 发现以前绑定的视图已重新附加,并尝试重新绑定现有资源。但是,它显然丢失了对静态可运行对象的引用。来自 ViewDataBinding 的相关源代码:
private static final OnAttachStateChangeListener ROOT_REATTACHED_LISTENER;
static {
if (VERSION.SDK_INT < VERSION_CODES.KITKAT) {
ROOT_REATTACHED_LISTENER = null;
} else {
ROOT_REATTACHED_LISTENER = new OnAttachStateChangeListener() {
@TargetApi(VERSION_CODES.KITKAT)
@Override
public void onViewAttachedToWindow(View v) {
// execute the pending bindings.
final ViewDataBinding binding = getBinding(v);
binding.mRebindRunnable.run();
v.removeOnAttachStateChangeListener(this);
}
@Override
public void onViewDetachedFromWindow(View v) {
}
};
}
}
我确实从以下位置注意到了相同的堆栈跟踪:App crash caused by data binding related to java.lang.Runnable android.databinding.ViewDataBinding.mRebindRunnable,但该问题似乎与应用程序立即崩溃有关(我的问题仅在尝试补充水分后发生)。但是从那个问题来看,我确实注意到记录我的视图标签返回空值。我尝试在 xml 中设置一个静态标签,没有任何变化。
我尝试过的其他事情:
- 如果我只实例化片段,则不会出现问题(但显然不会附加到框架布局
- 没有明确的调试崩溃点(onCreateView、onViewCreated都被调用了)
- 我试着改变我膨胀的方式,分配生命周期所有者,绑定视图模型;没有任何变化影响崩溃。
- 我尝试调用绑定(invalidateAll()、unbind())但没有成功。
同样,只有当应用程序实例仍然存在但 activity 已被销毁时,问题才会出现。感谢您的任何提示!!
编辑:相关代码位
Activity (Java) -
ExampleFragment exampleFragment = new ExampleFragment(exampleParameter);
FragmentManager fragmentManager = getSupportFragmentManager();
fragmentManager
.beginTransaction()
.add(R.id.example_frame_layout, exampleFragment, EXAMPLE_TAG)
.commit();
片段(Kotlin)-
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
binding = FragmentExampleBinding.inflate(inflater, container, false).apply {
lifecycleOwner = viewLifecycleOwner
}
return binding.root
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
binding.run {
viewModel = this@ExampleFragment.viewModel
}
}
更新
有趣的是,当我尝试将相同的片段(新实例化的)膨胀到不同的(未启动的)时,我现在看到了这一点 activity。调试这种情况,除了在膨胀并返回绑定的根视图(而不是 null)后遇到崩溃之外,我找不到任何问题。我已经尝试使用为布局创建的静态方法以及 DataBindingUtil。两者都经历了同样的崩溃。
尤里卡!!
不仅 <merge/>
不能用于 <include/>
布局(也记录在此处:https://developer.android.com/topic/libraries/data-binding/expressions#includes)
但是
绑定也不适用于根部有 <merge/>
的 <include/>
布局。这是它的样子:
<layout>
...
<include layout="id/sub_layout"
bind:viewModel="@{viewModel} />
...
</layout>
以及问题 (R.id.sub_layout.xml):
<layout>
...
<merge>
<TextView/>
<ImageView/>
</merge>
...
</layout>
奇怪的是,它似乎在启动 activity 时起作用,但很高兴知道导致此问题的症状(inflation 后异步崩溃)。 对于那些在数据绑定和错误消息方面遇到麻烦的人,我绝对建议尝试更改您的布局。