Android导航：片段之间的共享元素过渡不起作用

Question

我遵循了here的说明。

这是我的代码：

val navDirections = PostsListFragmentDirections.actionPostsListFragmentToPostDetailFragment(post)
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
   val animationExtras = FragmentNavigatorExtras(
      title to title.transitionName,
      body to body.transitionName
   )
   navigateWithAnimations(navDirections, animationExtras)
} else {
   navigateTo(navDirections)
}

[navigateTo和navigateWithAnimations是扩展功能：

fun Fragment.navigateTo(navDirections: NavDirections) {
    NavHostFragment.findNavController(this).navigate(navDirections)
}

fun Fragment.navigateWithAnimations(navDirections: NavDirections, extras: Navigator.Extras) {
    NavHostFragment.findNavController(this).navigate(navDirections, extras)
}

正在执行代码，但动画不起作用。

这里是nav_graph.xml

<fragment
   android:id="@+id/postsListFragment"
   android:name="PostsListFragment"
   android:label="PostsListFragment">
   <action          
      android:id="@+id/action_postsListFragment_to_postDetailFragment"
      app:destination="@id/postDetailFragment">
      <argument
         android:name="post"
         app:argType="Post"
         app:nullable="true"
         android:defaultValue="@null" />
   </action>
</fragment>
<fragment
   android:id="@+id/postDetailFragment"
   android:name="PostDetailsFragment"
   android:label="PostDetailFragment">
   <argument
      android:name="post"
      app:argType="Post"
      app:nullable="true"
      android:defaultValue="@null" />
</fragment>

这是将视图设置为第二个（目标片段）的方法：

private val args: PostDetailsFragmentArgs by navArgs()

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)

    args.post?.let { post ->
        tv_title.text = post.title
        tv_body.text = post.title
    }
}

在我定义的两个XML文件中：

android:transitionName="transition_title"
android:transitionName="transition_body"

Answer 1

您是否在第二个片段中建立了sharedElementEnterTransition属性？您必须在onCreate方法中执行以下操作：

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    main = requireActivity() as MainActivity
    sharedElementEnterTransition = ChangeBounds().apply {
        duration = 750
        interpolator = AccelerateDecelerateInterpolator()
    }
    sharedElementReturnTransition = ChangeBounds().apply {
        duration = 750
        interpolator = AccelerateDecelerateInterpolator()
    }
}

换句话说，接收片段需要知道如何处理共享元素。