Android – ViewDataBinding.inflate不会膨胀嵌套的自定义视图

我真的难住Android的视图通胀问题。 我看了其他示例代码使用android.databinding，我似乎无法理解为什么这不起作用。 任何有Android的经验的人可以提供一些建议？

我创建了一个简单的自定义视图：

class TestView(context: Context) : View(context) { private var testCallBack: TestCallback? = null fun setTestCallback(callback: TestCallback) { testCallBack = callback } interface TestCallback { fun test() } } 

然后把它包含在一个简单的布局中：

 <?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"> <android.support.constraint.ConstraintLayout android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".application.home.HomeActivity"> <com.test.TestView android:id="@+id/testView" android:layout_width="match_parent" android:layout_height="match_parent"/> </android.support.constraint.ConstraintLayout> </layout> 

然后我膨胀我的片段onCreateView方法的布局，并使用视图绑定库，尝试设置我的自定义视图的回调：

 class TestFragment : TiFragmentBase<TiPresenterHolder, TiView>(), TiView { override fun providePresenter(): TiPresenterHolder = TiPresenterHolder() override fun provideView(): TiView = this // Reference to the fragment's view binding private var viewBinding: FragmentTestBinding? = null override fun onCreateView(inflater: LayoutInflater?, container: ViewGroup?, savedInstanceState: Bundle?): View? { val _viewBinding = FragmentTestBinding.inflate(inflater ?: LayoutInflater.from(context)) _viewBinding.testView.setTestCallback(object: TestView.TestCallback { override fun test() { return } }) } } 

但是，我在_viewBinding.testView.setTestCallback(..)行上得到空指针异常。 这是堆栈跟踪：

 java.lang.NullPointerException: Attempt to invoke virtual method 'void com.test.TestView.setTestCallback(com.test.testview.TestViewCallback)' on a null object reference at com.test.TestFragment.onCreateView(TestFragment.kt:52) at android.support.v4.app.Fragment.performCreateView(Fragment.java:2354) at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1419) at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1740) at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1809) at android.support.v4.app.BackStackRecord.executeOps(BackStackRecord.java:799) at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2580) at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2367) at android.support.v4.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2322) at android.support.v4.app.FragmentManagerImpl.execSingleAction(FragmentManager.java:2199) at android.support.v4.app.BackStackRecord.commitNowAllowingStateLoss(BackStackRecord.java:651) at android.support.v4.app.FragmentStatePagerAdapter.finishUpdate(FragmentStatePagerAdapter.java:167) at android.support.v4.view.ViewPager.populate(ViewPager.java:1236) at android.support.v4.view.ViewPager.populate(ViewPager.java:1084) at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1614) at android.view.View.measure(View.java:22002) at android.support.constraint.ConstraintLayout.onMeasure(ConstraintLayout.java:1028) at android.view.View.measure(View.java:22002) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6580) at android.widget.FrameLayout.onMeasure(FrameLayout.java:185) at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:139) at android.view.View.measure(View.java:22002) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6580) at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1514) at android.widget.LinearLayout.measureVertical(LinearLayout.java:806) at android.widget.LinearLayout.onMeasure(LinearLayout.java:685) at android.view.View.measure(View.java:22002) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6580) at android.widget.FrameLayout.onMeasure(FrameLayout.java:185) at android.view.View.measure(View.java:22002) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6580) at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1514) at android.widget.LinearLayout.measureVertical(LinearLayout.java:806) at android.widget.LinearLayout.onMeasure(LinearLayout.java:685) at android.view.View.measure(View.java:22002) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6580) at android.widget.FrameLayout.onMeasure(FrameLayout.java:185) at com.android.internal.policy.DecorView.onMeasure(DecorView.java:721) at android.view.View.measure(View.java:22002) at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2410) at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1498) at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1751) at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1386) at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6733) at android.view.Choreographer$CallbackRecord.run(Choreographer.java:911) at android.view.Choreographer.doCallbacks(Choreographer.java:723) at android.view.Choreographer.doFrame(Choreographer.java:658) at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:897) at android.os.Handler.handleCallback(Handler.java:789) at android.os.Handler.dispatchMessage(Handler.java:98) at android.os.Looper.loop(Looper.java:164) 10-21 15:31:38.731 20659-20659/? E/AndroidRuntime: at android.app.ActivityThread.main(ActivityThread.java:6541) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)