android - Activity 结果后此 NavController 未知的导航目的地

Question

我正在使用导航 Controller 1.0.0alpha05，它工作得很好，但是当我在 Activity 结果后执行导航操作时，我正在为这个可怕的错误而苦苦挣扎。

我有一个单一的 Activity/多个 fragment 结构，特别是一个带有项目列表的 fragment 和另一个带有用于添加新项目的表单的 fragment 。

当我添加另一张没有任何图片的照片时，它正在工作并返回到带有项目列表的前一张，但是当我拍摄一些照片时，我在导航过程中遇到异常。

Caused by: java.lang.IllegalArgumentException: navigation destination XX is unknown to this NavController

Error log

包含 Action 的表单 fragment 的导航图:

<fragment
    android:id="@+id/idFormFragment"
    android:name="FormFragment"
    android:label="FormFragment"
    tools:layout="@layout/form_fragment">
    <argument
        android:name="idClient"
        android:defaultValue="-1"
        app:argType="integer" />
    <argument
        android:name="idServer"
        app:argType="string" />
    <action
        android:id="@+id/actionFormToList"
        app:destination="@id/idListFragment" />
</fragment>

带有安全参数的 Action 调用代码

FormFragmentDirections.ActionFormToList action = new FormFragmentDirections.ActionFormToList(sample.getIdJob());
Navigation.findNavController(getView()).navigate(action);

谢谢你的时间

Answer 1

好吧，我设法找到了一个荒谬的解决方案......

假设您正在使用从 NavHostFragment 扩展的主机导航 fragment ，将此 (Kotlin) 代码添加到其中:

/*
 * begin DUMB Navigation Component hack
 *
 * This fixes an IllegalArgumentException that can sometimes be thrown from within the
 * Navigation Architecture Component when you try to navigate after the Fragment has had its
 * state restored. It occurs because the navController's currentDestination field is null,
 * which stores where we currently are in the navigation graph. Because it's null, the
 * Navigation Component can't figure out our current position in relation to where we're
 * trying to navigate to, causing the exception to be thrown.
 *
 * This fix gives the navController a little nudge by gently setting it to where we currently
 * are in the navigation graph.
 *
 * This fix is verified as both working AND necessary as of Navigation Components version
 * 1.0.0-alpha07.
 *
 * There's a tiny bit more information at this thread, but it's pretty limited:
 * https://stackoverflow.com/questions/52101617/navigation-destination-unknown-to-this-navcontroller-after-an-activity-result
 */
private var checkCurrentDestination = false

override fun onStart() {
    super.onStart()

    if (checkCurrentDestination && navController.currentDestination == null) {
        navController.navigate(navController.graph.startDestination)
    }

    checkCurrentDestination = false
}

override fun onStop() {
    super.onStop()
    checkCurrentDestination = true
}
/*
 * end DUMB Navigation Component hack
 */

在 SEO 的努力中，堆栈跟踪将如下所示:

Caused by: java.lang.IllegalArgumentException: navigation destination XX is unknown to this NavController