Robolectric 尝试实例化 LayoutParams 对象时出现 NPE

Question

我有一个 Fragment 实现，我想使用 Robolectric 框架对其进行测试。当我尝试运行测试时，它失败并出现异常：

java.lang.NullPointerException 
at org.robolectric.shadows.ShadowViewGroup$ShadowLayoutParams.__constructor__(ShadowViewGroup.java:141)
at android.view.ViewGroup$LayoutParams.<init>(ViewGroup.java)   
at android.view.ViewGroup$MarginLayoutParams.<init>(ViewGroup.java)     
at android.widget.FrameLayout$LayoutParams.<init>(FrameLayout.java)     
at com.lalala.ui.FullPickerFragment.onCreateView(FullPickerFragment.java:41)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1067)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1248)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:738)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1613)
at android.support.v4.app.FragmentManagerImpl.run(FragmentManager.java:517)
at android.os.Handler.handleCallback(Handler.java:739)  
at android.os.Handler.dispatchMessage(Handler.java:95)  
at org.robolectric.shadows.ShadowMessageQueue.dispatchMessage(ShadowMessageQueue.java:130)
at org.robolectric.shadows.ShadowMessageQueue.access0(ShadowMessageQueue.java:29)
at org.robolectric.shadows.ShadowMessageQueue.run(ShadowMessageQueue.java:95)
at org.robolectric.util.Scheduler.runOrQueueRunnable(Scheduler.java:230)
at org.robolectric.util.Scheduler.postAtFrontOfQueue(Scheduler.java:98)
at org.robolectric.shadows.ShadowMessageQueue.enqueueMessage(ShadowMessageQueue.java:114)
at android.os.MessageQueue.enqueueMessage(MessageQueue.java)    
at android.os.Handler.enqueueMessage(Handler.java:631)  
at android.os.Handler.sendMessageAtTime(Handler.java:600)   
at android.os.Handler.sendMessageDelayed(Handler.java:570)  
at android.os.Handler.post(Handler.java:326)    
at android.support.v4.app.FragmentManagerImpl.enqueueAction(FragmentManager.java:1519)
at android.support.v4.app.BackStackRecord.commitInternal(BackStackRecord.java:634)
at android.support.v4.app.BackStackRecord.commit(BackStackRecord.java:613) 
at com.lalala.ui.FullPickerFragmentTest.init(FullPickerFragmentTest.java:137)
at org.junit.runners.model.FrameworkMethod.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:24)
at org.robolectric.RobolectricTestRunner.evaluate(RobolectricTestRunner.java:245)
at org.robolectric.RobolectricTestRunner.runChild(RobolectricTestRunner.java:185)
at org.robolectric.RobolectricTestRunner.runChild(RobolectricTestRunner.java:54)
at org.junit.runners.ParentRunner.run(ParentRunner.java:290)  
at org.junit.runners.ParentRunner.schedule(ParentRunner.java:71)  
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)    
at org.junit.runners.ParentRunner.access[=11=]0(ParentRunner.java:58)  
at org.junit.runners.ParentRunner.evaluate(ParentRunner.java:268)     
at org.robolectric.RobolectricTestRunner.evaluate(RobolectricTestRunner.java:149)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)    
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)   
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:234)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:74)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)

在这一行标有 @Before 注释的测试用例方法中失败：

activity.getSupportFragmentManager()
   .beginTransaction()
   .add(pickerFragment, TAG)
   .commit();

FullPicketFragment 引用的代码位于 onCreateView 方法中，这里是：

public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        Log.d(LOG_TAG, "onCreateView()");
        fragmentView = inflater.inflate(R.layout.bf_full_picker, container, false);
        mFragmentViewContainer = new FrameLayout(getActivity());
        ViewGroup.LayoutParams fragmentViewParams = fragmentView.getLayoutParams();
        FrameLayout.LayoutParams fragmentViewContainerParams =
                new FrameLayout.LayoutParams(fragmentViewParams);
        mFragmentViewContainer.setLayoutParams(fragmentViewContainerParams);
        mFragmentViewContainer.addView(fragmentView);
        return mFragmentViewContainer;
    }

如您所见，我只是膨胀布局并将其放入 FrameLayout 中，并从膨胀的布局中复制 LayoutParams 属性。 Robolectric 无法创建 LayoutParams 对象。

我该如何解决这个问题？

我尝试使用另一个构造函数创建 LayoutParams 的副本，但没有帮助。此外，代码本身工作正常，问题仅出现在测试用例初始化中。在我在 onCreateView.

中进行这些更改之前，测试工作正常

我正在使用 Robolectric 3.0-rc3.

Answer 1

似乎fragmentView.getLayoutParams() returns null and line 在它被放入构造函数之后。你可以试试这个：

public View onCreateView(...) {
    mFragmentViewContainer = new FrameLayout(inflater.getContext());
    fragmentView = inflater.inflate(
            R.layout.bf_full_picker, 
            mFragmentViewContainer, 
            **true**);
    return mFragmentViewContainer;
}

Robolectric 尝试实例化 LayoutParams 对象时出现 NPE

NPE in Robolectric when trying to instantiate LayoutParams object

android

robolectric

android-testing