在自定义 View 布局中使用包含标记时 Android 数据绑定(bind)崩溃

Question

我正在尝试使用 include 标记将一些自定义 View 添加到我使用 DataBinding 的 Activity 布局中。我的自定义 View 也在使用 DataBinding。但是我在应用程序启动时崩溃了:

05-02 17:30:03.685 12595-12595/? E/AndroidRuntime: FATAL EXCEPTION: main
                                                   Process: com.novachevskyi.databindingtest, PID: 12595
                                                   java.lang.RuntimeException: Unable to start activity ComponentInfo{com.novachevskyi.databindingtest/com.novachevskyi.databindingtest.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.novachevskyi.databindingtest.databinding.CustomViewBinding.invalidateAll()' on a null object reference
                                                       at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
                                                       at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
                                                       at android.app.ActivityThread.-wrap11(ActivityThread.java)
                                                       at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
                                                       at android.os.Handler.dispatchMessage(Handler.java:102)
                                                       at android.os.Looper.loop(Looper.java:148)
                                                       at android.app.ActivityThread.main(ActivityThread.java:5417)
                                                       at java.lang.reflect.Method.invoke(Native Method)
                                                       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
                                                       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
                                                    Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.novachevskyi.databindingtest.databinding.CustomViewBinding.invalidateAll()' on a null object reference
                                                       at com.novachevskyi.databindingtest.databinding.ActivityMainBinding.invalidateAll(ActivityMainBinding.java:41)
                                                       at com.novachevskyi.databindingtest.databinding.ActivityMainBinding.<init>(ActivityMainBinding.java:33)
                                                       at com.novachevskyi.databindingtest.databinding.ActivityMainBinding.bind(ActivityMainBinding.java:105)
                                                       at android.databinding.DataBinderMapper.getDataBinder(DataBinderMapper.java:11)
                                                       at android.databinding.DataBindingUtil.bind(DataBindingUtil.java:185)
                                                       at android.databinding.DataBindingUtil.bindToAddedViews(DataBindingUtil.java:299)
                                                       at android.databinding.DataBindingUtil.setContentView(DataBindingUtil.java:279)
                                                       at android.databinding.DataBindingUtil.setContentView(DataBindingUtil.java:261)
                                                       at com.novachevskyi.databindingtest.MainActivity.onCreate(MainActivity.java:11)
                                                       at android.app.Activity.performCreate(Activity.java:6251)
                                                       at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
                                                       at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
                                                       at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) 
                                                       at android.app.ActivityThread.-wrap11(ActivityThread.java) 
                                                       at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) 
                                                       at android.os.Handler.dispatchMessage(Handler.java:102) 
                                                       at android.os.Looper.loop(Looper.java:148) 
                                                       at android.app.ActivityThread.main(ActivityThread.java:5417) 
                                                       at java.lang.reflect.Method.invoke(Native Method) 
                                                       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
                                                       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 

主要 Activity :

public class MainActivity extends AppCompatActivity {
  @Override protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    DataBindingUtil.setContentView(this, R.layout.activity_main);
  }
}

自定义 View :

public class CustomView extends LinearLayout {
  public CustomView(Context context, AttributeSet attrs) {
    super(context, attrs);
  }

  @Override protected void onFinishInflate() {
    super.onFinishInflate();
    DataBindingUtil.bind(this);
  }
}

activity_main.xml:

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

  <RelativeLayout
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:paddingLeft="@dimen/activity_horizontal_margin"
      android:paddingRight="@dimen/activity_horizontal_margin"
      android:paddingTop="@dimen/activity_vertical_margin"
      android:paddingBottom="@dimen/activity_vertical_margin"
      tools:context="com.novachevskyi.databindingtest.MainActivity">

    <include layout="@layout/custom_view"/>

  </RelativeLayout>

</layout>

自定义 View .xml:

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

  <com.novachevskyi.databindingtest.CustomView
      android:layout_width="match_parent"
      android:layout_height="match_parent">

    <TextView
        android:text="Hello World!"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>

  </com.novachevskyi.databindingtest.CustomView>

</layout>

我还使用示例项目创建了公共(public)存储库: https://github.com/novachevskyi/DataBinding-issue

我在 com.android.tools.build:gradle:1.3.1 中使用数据绑定(bind)，现在，当我尝试将构建工具版本升级到 com.android 时。 tools.build:gradle:2.1.0，我的所有包含 include xml 标记的 View 都面临这样的问题。如果您能提供有关上述问题的任何信息，我们将不胜感激。

Answer 1

我查看了您的项目并运行了它。我认为它崩溃的原因是因为

@Override protected void onFinishInflate() {
    super.onFinishInflate();
    DataBindingUtil.bind(this);
}

如果删除 DataBindingUtil.bind(this)它会停止崩溃。原因是绑定(bind)调用正在寻找 <layout>围绕 View 但它找不到它所以它抛出异常。由于 CustomView 正在调用自身的绑定(bind)，因此它没有被任何导致 ViewDataBinding 的东西包围至 throw new IllegalArgumentException("View is not a binding layout")

我不完全确定你想要实现什么但调用 bind onFinishInflate 内部将是多余的，因为 Activity 在绑定(bind) Activity 的布局时会为您执行此操作。如果您需要 CustomView 内的绑定(bind)您可以执行以下操作:

@Override protected void onAttachedToWindow() {
  super.onAttachedToWindow();
  CustomViewBinding binding = DataBindingUtil.findBinding(this);
}