android - NPE @ android.support.v7.widget.RecyclerView$LayoutManager.detachViewInternal

从 espresso 2.0 切换到 2.1 时，我遇到了这个奇怪的错误:

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.ChildHelper.detachViewFromParent(int)' on a null object reference
    at android.support.v7.widget.RecyclerView$LayoutManager.detachViewInternal(RecyclerView.java:5407)
    at android.support.v7.widget.RecyclerView$LayoutManager.detachViewAt(RecyclerView.java:5400)
    at android.support.v7.widget.RecyclerView.setAdapterInternal(RecyclerView.java:647)
    at android.support.v7.widget.RecyclerView.swapAdapter(RecyclerView.java:594)
    at org.ligi.passandroid.ui.PassListActivity.onCreate(PassListActivity.java:161)
    at android.app.Activity.performCreate(Activity.java:5990)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
    at android.support.test.runner.MonitoringInstrumentation.callActivityOnCreate(MonitoringInstrumentation.java:489)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
    at android.app.ActivityThread.access$800(ActivityThread.java:151)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
    at android.os.Handler.dispatchMessage(Handler.java:102)
    at android.os.Looper.loop(Looper.java:135)
    at android.app.ActivityThread.main(ActivityThread.java:5257)
    at java.lang.reflect.Method.invoke(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:372)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)

那里的代码:

 @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        supportRequestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);
        setContentView(R.layout.pass_list);
        ButterKnife.inject(this);

        AXT.at(openFileFAB).setVisibility(Build.VERSION.SDK_INT >= VERSION_STARTING_TO_SUPPORT_STORAGE_FRAMEWORK);

        final LinearLayoutManager llm = new LinearLayoutManager(this);
        llm.setOrientation(LinearLayoutManager.VERTICAL);
        (!!here!!) recyclerView.setLayoutManager(llm);

当我只是运行应用程序或使用 espresso 2.0 测试它时，它并没有在那里崩溃

最佳答案

这是一个奇怪的问题，所以我将首先给出一个对我有用的解决方案，然后尝试解释我认为正在发生的事情。

快速修复是在测试构建配置中重新声明您的支持库依赖项:

androidTestCompile 'com.android.support:support-v4:22.1.1'
androidTestCompile 'com.android.support:appcompat-v7:22.1.1'
androidTestCompile 'com.android.support:cardview-v7:22.1.1'
androidTestCompile 'com.android.support:gridlayout-v7:22.1.1'
androidTestCompile 'com.android.support:recyclerview-v7:22.1.1'

这应该可以解决您的问题。

解释很奇怪:看起来 espresso-contrib:2.1 依赖于旧版本的 com.android.support:recyclerview-v7:22.0.0 。这可以使用 Gradle app:dependencies task: ./gradlew app:dependencies 来检查。不知何故，此依赖项优先于 compile 中声明的依赖项，并将其下拉到旧版本:

+--- com.android.support.test.espresso:espresso-contrib:2.1
|    +--- com.android.support:recyclerview-v7:22.0.0
|    |    \--- com.android.support:support-v4:22.0.0
|    +--- com.android.support:support-v4:22.0.0
|    \--- com.android.support.test.espresso:espresso-core:2.1 (*)

这可以使用 app:dependencyInsight 任务来确认:./gradlew app:dependencyInsight --configuration androidTestCompile --dependency recyclerview-v7

com.android.support:recyclerview-v7:22.0.0
\--- com.android.support.test.espresso:espresso-contrib:2.1
     \--- androidTestCompile

结果是测试构建使用了不同(顺序)版本的 recyclerview-v7，结果证明是错误的。添加 androidTestCompile 有助于 Gradle 检测冲突并正确解决它。修复后:

com.android.support:recyclerview-v7:22.1.1 (conflict resolution)
\--- androidTestCompile

com.android.support:recyclerview-v7:22.0.0 -> 22.1.1
\--- com.android.support.test.espresso:espresso-contrib:2.1
     \--- androidTestCompile

关于android - NPE @ android.support.v7.widget.RecyclerView$LayoutManager.detachViewInternal，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/30008836/