Android：将视图从父级转移到另一个

Question

我来这里帮忙，因为我完全不明白我的代码不起作用。 快一点，我的目标是“重新加载”一个表示列表项的视图。由于我的列表项可以在其子项中包含其他列表项，因此我想扩充一个新的列表项，然后将这些子项从旧项转移到新项。

我得到一个“指定的孩子已经有一个父母。您必须首先在孩子的父母上调用 removeView()。”错误，但我确实在孩子的父母上调用了 removeView（不知何故它不起作用）（请参阅我的代码）

这是我的布局的设计方式（我删除了一些行，以便更具可读性）：

<?xml version="1.0" encoding="utf-8"?>
 <layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools">

    <data>
        <variable
            name="mainListItem"
            type="com.plg.lirs.data.LirsDataEntity" />
    </data>

    <LinearLayout android:id="@+id/main_list_item_global_layout">

        <LinearLayout android:id="@+id/main_list_item_parent_layout"
            app:mainListItemParentLayout="@{mainListItem}">

        <!-- contains a bunch of views and stuff, nothing important here -->

        </LinearLayout>

        <LinearLayout android:id="@+id/main_list_item_children_layout"
            android:animateLayoutChanges="true">

        <!-- here are all the children i want to transfer, all the children here are inflated from this layout -->

        </LinearLayout>

    </LinearLayout>

</layout>

现在这里是我的代码来扩展这个布局：

/* entity is just a logical class that contains my data
olderView is the old view representing the old list item */
private fun inflateItem(entity: LirsDataEntity, olderView: View? = null) : View {
        val itemBinding = DataBindingUtil.inflate<MainListItemBinding>(inflater, R.layout.main_list_item, null, false, null)
       // the itemBinding.root will be added into the parent's children layout later on, after this function
       // + i've tried with true as attachToParent, doesn't change

       /* HERE is the core of the problem. My goal is : if an olderView is provided, then transfer the children from the old one to the new one */
        if(olderView != null) {
            val olderChildrenLayout = olderView.findViewById<LinearLayout>(R.id.main_list_item_children_layout) // here is the LinearLayout that contains the children
            val children = olderChildrenLayout.children
            children.forEach {
                olderChildrenLayout.removeView(it) // remove the children from the old parent
                itemBinding.mainListItemChildrenLayout.addView(it) // add it to the new parent
                // at this point i get the error
            }
        }

        entity.ui.reset() // not important here
        itemBinding.mainListItem = entity 

        /* some listeners are set here */

        return itemBinding.root
    }

感谢阅读！

Answer 1

我发现出了什么问题。 当调用 removeView() 时，android 会尝试对其进行动画处理，从而将子视图放入包含当前正在动画的子视图的变量中。然后，当尝试更改子视图的父视图（我们希望为空）时，它会检查当前视图是否正在动画。确实，父母没有改变（至少现在，我不知道以后是否会改变）。这就是为什么我们不能调用 addView()。

解决办法是把 LayoutTransition 类存起来，然后设置为 null，做传输，然后重置。它不会为孩子们设置动画，但至少它会起作用。

这里有一小段代码来完成这项工作：

public class JavaUtils {
    public static void transferChildren(@NotNull final ViewGroup depart, @NotNull final ViewGroup arrival) {
        LayoutTransition transition = depart.getLayoutTransition();
        depart.setLayoutTransition(null);
            while(depart.getChildCount() > 0) {
            View c = depart.getChildAt(0);
            depart.removeViewAt(0);
            arrival.addView(c);
        }
        depart.setLayoutTransition(transition);
    }
}

对于 Kotlin 用户：

fun ViewGroup.transferChildrenTo(arrival: ViewGroup) {
    val transition: LayoutTransition = layoutTransition
    layoutTransition = null
    while (childCount > 0) {
        val c: View = getChildAt(0)
        removeViewAt(0)
        arrival.addView(c)
    }
    layoutTransition = transition
}