Android数据绑定：将变量传递给NavigationView

时间：2018-03-27 22:01:15

标签： android android-layout android-databinding

当用户登录我的应用并在MainActivity收到他们的个人资料信息（姓名，头像等）时，我想通过用户参数填充导航视图标题中的某些字段数据绑定。我已尝试过the docs中提出的方法，但可能仅限于<include />？

activity_main.xml中 

<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <data>

        <variable
            name="user"
            type="com.example.app.models.User" />
    </data>

    <android.support.v4.widget.DrawerLayout 
        // layout params... >

        <include
            layout="@layout/app_bar_main"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />

        <android.support.design.widget.NavigationView xmlns:bind="http://schemas.android.com/apk/res-auto"
            android:id="@+id/nav_view"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:layout_gravity="start"
            android:fitsSystemWindows="true"
            app:headerLayout="@layout/nav_header_main"
            app:menu="@menu/activity_main_drawer"
            bind:user="@{user}" />

    </android.support.v4.widget.DrawerLayout>
</layout>

nav_header_main.xml 

<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto">

<data>

    <variable
        name="user"
        type="com.example.app.models.User" />
</data>

<LinearLayout
    // layout params... >

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:paddingTop="@dimen/nav_header_vertical_spacing"
        android:text="@{user.name}"
        android:textAppearance="@style/TextAppearance.AppCompat.Body1" />

</LinearLayout>
</layout>

MainActivity 

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    ActivityMainBinding binding = DataBindingUtil.setContentView(this, R.layout.activity_main);
    binding.setUser(User.getInstance());
// other stuff...
}

我收到2个错误：

  1. 错误：找不到符号类ActivityMainBinding
  2. 无法找到属性的设定者＆＃39; bind：user＆＃39;在android.support.design.widget.NavigationView上使用参数类型com.example.app.models.User。

    3. 如果我删除它构建的bind:user行，但它当然不起作用。有什么方法可以让这种事情发挥作用吗？

5 个答案:

答案 0 :(得分：0)

您需要以编程方式添加导航视图以启用绑定。 

NavHeaderHomeBinding _bind = DataBindingUtil.inflate(getLayoutInflater(), R.layout.nav_header_main, binding
            .navView, false);
    binding.navView.addHeaderView(_bind);

您的xml：删除headerLayout 

<android.support.design.widget.NavigationView xmlns:bind="http://schemas.android.com/apk/res-auto"
        android:id="@+id/nav_view"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:fitsSystemWindows="true"
        app:menu="@menu/activity_main_drawer"
        bind:user="@{user}" />

这应该有用。

答案 1 :(得分：0)

这对我有用：

activity_main.xml 

<?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">

    <androidx.drawerlayout.widget.DrawerLayout
            android:id="@+id/drawer_layout"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:fitsSystemWindows="true"
            tools:openDrawer="start">

        <include
                layout="@layout/app_bar_main"
                android:layout_width="match_parent"
                android:layout_height="match_parent"/>

        <com.google.android.material.navigation.NavigationView
                android:id="@+id/nav_view"
                android:layout_width="wrap_content"
                android:layout_height="match_parent"
                android:layout_gravity="start"
                android:fitsSystemWindows="true"
                app:headerLayout="@layout/nav_header_main"
                app:menu="@menu/activity_main_drawer"/>

    </androidx.drawerlayout.widget.DrawerLayout>

</layout>

nav_header_main.xml 

<?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"
        android:id="@+id/layout_nav_view_header">

    <data>
        <variable
                name="user"
                type="com.myapp.model.UserSettings"/>
    </data>

    <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="@dimen/nav_header_height"
            android:background="@drawable/side_nav_bar"
            android:paddingBottom="@dimen/activity_vertical_margin"
            android:paddingLeft="@dimen/activity_horizontal_margin"
            android:paddingRight="@dimen/activity_horizontal_margin"
            android:paddingTop="@dimen/activity_vertical_margin"
            android:theme="@style/ThemeOverlay.AppCompat.Dark"
            android:orientation="vertical"
            android:gravity="bottom">

        <ImageView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:paddingTop="@dimen/nav_header_vertical_spacing"
                app:srcCompat="@mipmap/ic_launcher_round"
                android:contentDescription="@string/nav_header_desc"
                android:id="@+id/imageView"/>

        <TextView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:paddingTop="@dimen/nav_header_vertical_spacing"
                android:text="@{user.name}"
                android:textAppearance="@style/TextAppearance.AppCompat.Body1"/>

        <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="@string/nav_header_subtitle"
                android:id="@+id/textView"/>

    </LinearLayout>

</layout>

然后在活动的onCreate中：

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)

    val viewHeader = nav_view.getHeaderView(0)
    val navViewHeaderBinding : NavHeaderMainBinding = NavHeaderMainBinding.bind(viewHeader)
    navViewHeaderBinding.user = UserSettings(null, null, "John Doe", "Android Developer", null)
}

答案 2 :(得分：0)

ksinghit的答案对我不起作用。由于某种原因，当我尝试通过XML绑定用户变量时，Gradle无法构建。 但是根据他的回答，我能够删除id_transaction !== null ? id_transaction : ' - ' info_data !== null ? info_data.value1 : ' - ' bio_data.digital[0] !== undefined ? bio_data.digital[0].name] : '-' 行并以编程方式设置变量：

bind:user

使用Kotlin对其他任何人进行观察：添加Header View时，您必须传递视图根目录，而不传递NavHeaderHomeBinding本身：

_bind.user = user

答案 3 :(得分：0)

<com.google.android.material.navigation.NavigationView
  android:id="@+id/nav_view"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:layout_gravity="start"
  app:menu="@menu/activity_navigation_drawer"
  android:theme="@style/NavigationDrawerStyle">

  <include layout="@layout/nav_header_navigation"
    app:user= "@{user}"/>
</com.google.android.material.navigation.NavigationView>

答案 4 :(得分：0)

@AndroidDev 的答案基本上对我有用，对我来说似乎是最干净的。 但我尝试将 viewModel 设置为数据绑定变量并在导航头视图中访问其 LiveData 实例和方法：

nav_header_main.xml:

<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="viewModel"
        type="com.example.MainActivityViewModel" />
</data>

<androidx.constraintlayout.widget.ConstraintLayout
    android:layout_width="match_parent"
    android:layout_height="176dp"
    android:background="?attr/colorPrimary">

    <Button
        android:id="@+id/login_logout_button"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:onClick="@{() -> viewModel.handleLoginLogoutButton()}"
        android:text='@{viewModel.user == null ? "Login" : "Logoff"}'
        android:textAlignment="viewStart"
        android:textAllCaps="false"
        android:textAppearance="@style/textstyle_button"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        tools:text='Abmelden' />

    <TextView
        android:id="@+id/account_address"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:text="@{viewModel.user.email}"
        android:textAppearance="@style/textstyle_body1"
        android:textColor="@color/white"
        android:visibility="@{viewModel.userCredentialsVisibility}"
        app:layout_constraintBottom_toTopOf="@+id/login_logout_button"
        app:layout_constraintStart_toStartOf="parent"
        tools:text="kuku@gmail.com"
        tools:visibility="visible" />
  ...
    </androidx.constraintlayout.widget.ConstraintLayout>
</layout>

这起初不起作用，因为 viewModel-LiveData-changes 没有传播到生成的 NavHeaderMainBinding 实例。

我很头疼，我确实在我的 ViewModel 中实现了 Observable 接口，如官方数据绑定文档中所述：https://developer.android.com/topic/libraries/data-binding/architecture#observable-viewmodel

但这并没有解决这个特定问题。 然后我想起了 databinding-docs 提到在生成的 Binding-class 上设置 LifeCycleOwner。我为 NavHeaderMainBinding 做了这个，现在它正在工作：

MainActivity.kt：

override fun onPostCreate(savedInstanceState: Bundle?) {
    super.onPostCreate(savedInstanceState)
    // ...
    // this has to be in onPostCreate to avoid a IllegalStateException
    // while using FragmentContainerView as NavHost in MainActivity (activity_main.xml)
    navController = findNavController(R.id.nav_host_fragment)

    val navigationView = findViewById<NavigationView>(R.id.nav_view)
    navigationView.setupWithNavController(navController)
    // we have to bind the viewModel manually to the header-view
    // since NavigationView does not support databinding by itself
    val headerView = navigationView.getHeaderView(0)
    val headerViewBinding = NavHeaderMainBinding.bind(headerView)
    headerViewBinding.viewModel = mainActivityViewModel
    // this new line is important to get notifications about livedata-changes!!!
    headerViewBinding.lifecycleOwner = this
    // ...
}

现在完美运行！

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