Question

我尝试使用include标记将一些自定义视图添加到使用DataBinding的活动布局中。我的自定义视图也使用DataBinding。但是我在申请开始时遇到了崩溃：

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)

MainActivity：

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

CustomView：

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中：

<?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>

custom_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>

我还创建了带有示例项目的公共回购： https://github.com/novachevskyi/DataBinding-issue

我正在使用com.android.tools.build:gradle:1.3.1的数据绑定，现在，当我尝试将构建工具版本升级到com.android.tools.build:gradle:2.1.0时，我的所有观点都包含此类问题include xml标记。对于有关上述问题的任何信息，我们将不胜感激。

Answer 1

我看了一下你的项目并运行它。我认为它崩溃的原因是因为

DataBindingUtil.bind(this)

如果您删除<layout>，它将停止崩溃。原因是绑定调用正在查找围绕视图的ViewDataBinding，但它无法找到它，因此会抛出异常。由于CustomView正在调用bind本身，因此它不会被导致throw new IllegalArgumentException("View is not a binding layout") bind的任何内容所包围

我不完全确定您尝试实现的目标，但在onFinishInflate内调用CustomView将是多余的，因为活动在绑定布局时为您执行此操作为了活动。如果您需要@Override protected void onAttachedToWindow() { super.onAttachedToWindow(); CustomViewBinding binding = DataBindingUtil.findBinding(this); }类中的绑定，您可以执行以下操作：

{{1}}

Answer 2

@ SeptimusX75的答案无效，因为DataBindingUtil.findBinding(this)在内部调用this.getTag(R.id.dataBinding)以获取绑定，但是在调用onFinishInflate时尚未设置标签。

当需要使用绑定时，尝试通过this.getTag(R.id.dataBinding);获取绑定。

public class CustomView extends LinearLayout {
    // ...
    public CustomViewBinding binding;
    // ...
    public void setTitle(final String text) {
        if (binding == null) {
            binding = Objects.requireNonNull(getTag(R.id.dataBinding));
        }
        binding.title.setText(text);
    }
}

或者，在调用CustomView上的任何方法之前，从活动中手动设置绑定。

public class CustomView extends LinearLayout {
    // ...
    public CustomViewBinding binding;
    // ...
    public void setBinding(final CustomViewBinding binding) {
        this.binding = binding;
    }
}

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

Answer 3

万一其他人犯了我犯下的er..dumb错误...

当我错误地有两个重复的布局文件，一个使用数据绑定，另一个没有使用...时，发生了此错误。

删除重复项为我解决了错误。

Answer 4

工具栏中的“转到生成”选项，然后选择“重建项目”。

将include标记与自定义视图布局一起使用时，Android数据绑定崩溃

4 个答案: