androidx.navigation:navigation-fragment:2.2.0，在 navController.popBackStack() 上获取 "You must call removeView() on the child's parent first."

Question

我喜欢使用数据绑定和导航图。但是在从 androidx.navigation:navigation-fragment:2.0.0 更新 androidx 依赖项后，2.2.0 应用程序在按下按钮 "Back" 后崩溃。从其他片段到包含 FragmentPagerAdapter.

的前一个片段 return 之后总是崩溃

在build.gradle

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])

    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'

//    This is work
//    implementation 'androidx.appcompat:appcompat:1.0.2'
//    implementation 'androidx.navigation:navigation-fragment:2.0.0'

//  This generate error after backstack
    implementation 'androidx.appcompat:appcompat:1.1.0'
    implementation 'androidx.navigation:navigation-fragment:2.2.0'
}

如需查看问题和错误，请从 https://github.com/ABRadzh/ErrorNavigation 下载示例。不然我很难解释哪里出错了

按任意页面上的任意按钮。
按下硬件 "Back" 按钮。
获取错误信息：

2020-02-11 16:15:13.119 2429-2429/in.pagerview.navigation.databinding.onbackstack E/AndroidRuntime: FATAL EXCEPTION: main
    Process: in.pagerview.navigation.databinding.onbackstack, PID: 2429
    java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child's parent first.
        at android.view.ViewGroup.addViewInner(ViewGroup.java:4954)
        at android.view.ViewGroup.addView(ViewGroup.java:4785)
        at androidx.viewpager.widget.ViewPager.addView(ViewPager.java:1485)
        at android.view.ViewGroup.addView(ViewGroup.java:4725)
        at android.view.ViewGroup.addView(ViewGroup.java:4698)
        at androidx.fragment.app.FragmentStateManager.createView(FragmentStateManager.java:326)
        at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1187)
        at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1356)
        at androidx.fragment.app.FragmentManager.moveFragmentToExpectedState(FragmentManager.java:1434)
        at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1497)
        at androidx.fragment.app.FragmentManager.dispatchStateChange(FragmentManager.java:2625)
        at androidx.fragment.app.FragmentManager.dispatchActivityCreated(FragmentManager.java:2577)
        at androidx.fragment.app.Fragment.performActivityCreated(Fragment.java:2722)
        at androidx.fragment.app.FragmentStateManager.activityCreated(FragmentStateManager.java:346)
        at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1188)
        at androidx.fragment.app.FragmentManager.addAddedFragments(FragmentManager.java:2224)
        at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:1997)
        at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:1953)
        at androidx.fragment.app.FragmentManager.execPendingActions(FragmentManager.java:1849)
        at androidx.fragment.app.FragmentManager.run(FragmentManager.java:413)
        at android.os.Handler.handleCallback(Handler.java:790)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6719)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:449)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)

但是转换片段和数据绑定的所有代码都是自动生成的。我不知道我必须在哪里调用 removeView()。

如果您尝试使用旧的依赖项，请反转代码和布局中的所有注释。 popBackStack() 将正常工作。

我没有发现任何关于这个错误的信息。可能是我做错了什么？

Answer 1

解决方案就是将这段代码添加到每个片段中：

@Override
public void onDestroyView() {
    super.onDestroyView();
    if(binding.getRoot().getParent() != null)
        ((ViewGroup)binding.getRoot().getParent()).removeView(binding.getRoot());
}

我真的建议您创建一个包含此代码的 BaseFragment，每个片段都将从它扩展，这样您就不必在每个片段上重复代码 class。

androidx.navigation:navigation-fragment:2.2.0，在 navController.popBackStack() 上获取 "You must call removeView() on the child's parent first."

androidx.navigation:navigation-fragment:2.2.0, get "You must call removeView() on the child's parent first." on navController.popBackStack()

android-pageradapter

android-databinding

android-navigation-graph