如何将数据变量传递给包含的布局？

Question

有没有办法将数据变量传递给包含的布局？

父布局

<?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"
    tools:showIn="@layout/fragment_settings">

    <data>

        <variable
            name="viewModel"
            type="......settings.SettingsFragmentViewModel" />
    </data>

    <androidx.constraintlayout.widget.ConstraintLayout
        android:id="@+id/content"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:animateLayoutChanges="true"
        android:overScrollMode="never"
        android:padding="@dimen/spacing_default">

        <include
            android:id="@+id/main"
            layout="@layout/layout_settings_main" />

    </androidx.constraintlayout.widget.ConstraintLayout>

并希望在包含的布局中包含 viewModel

<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"
    tools:showIn="@layout/fragment_settings">

    <data>

        <variable
            name="viewModel"
            type="......settings.SettingsFragmentViewModel" />
    </data>

    <merge>
...........

或者只有这样设置才有可能：

 binding = FragmentSettingsBinding.inflate(inflater, container, false).apply {
            lifecycleOwner = this@SettingsFragment
            viewModel = this@SettingsFragment.viewModel
            main.viewModel = this@SettingsFragment.viewModel
        }

Answer 1

好吧，在本文开头我已经说过，这取决于是否可以将变量传递给辅助布局。原因如下： 数据绑定不支持包含作为合并元素的直接子元素。例如，不支持以下布局：

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:bind="http://schemas.android.com/apk/res-auto">
   <data>
       <variable name="user" type="it.communikein.myunimib.User"/>
   </data>
   <merge>
       <include layout="@layout/name"
           bind:user="@{user}"/>
       <include layout="@layout/contact"
           bind:user="@{user}"/>
   </merge>
</layout>

Answer 2

在父 xml 内 include 标记中，使用 bind:viewModel 将数据变量传递给包含的布局。

<?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"
xmlns:bind="http://schemas.android.com/apk/res-auto"
tools:showIn="@layout/fragment_settings">

<data>

    <variable
        name="viewModel"
        type="......settings.SettingsFragmentViewModel" />
</data>

<androidx.constraintlayout.widget.ConstraintLayout
    android:id="@+id/content"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:animateLayoutChanges="true"
    android:overScrollMode="never"
    android:padding="@dimen/spacing_default">

    <include
        android:id="@+id/main"
        layout="@layout/layout_settings_main"
        bind:viewModel="@{viewModel}" />

</androidx.constraintlayout.widget.ConstraintLayout>

您包含的布局将在viewModel 中获得对象实例。

更多详情请查看this教程

Answer 3

打开 build.grade 并在块 android{ // ...} 中添加 dataBinding { enabled = true }