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

Question

当我从 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);

当我运行应用程序或使用 espresso 2.0 对其进行测试时，它不会在那里崩溃

Answer 1

这是一个奇怪的问题，所以我会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:看起来像 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 任务进行检查:./gradlew app:dependencies。这种依赖性以某种方式优先于编译中声明的依赖性并将其拉低到旧版本:

+--- 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冲突。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