在我的布局文件中使用CardView和RecyclerView会抛出异常。

Question

我一直在尝试着使用 Android Preview L 的 Material Design。我导入了 CardView 和 RecyclerView 库。

我使用的是 Android Studio 预览版 0.8.0，并安装了最新的 SDK 包。

但是，一旦我在我的布局文件中使用它们，预览器就会对它们中的每一个都抛出异常。

这里是 CardView 的异常：

java.lang.ClassFormatError: Illegal field name "CardView.Dark" in class android/support/v7/cardview/R$style
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:792)
at java.lang.ClassLoader.defineClass(ClassLoader.java:635)
at org.jetbrains.android.uipreview.ProjectClassLoader.findClass(ProjectClassLoader.java:63)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at java.lang.ClassLoader.loadClass(ClassLoader.java:411)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at android.support.v7.widget.CardView.initialize(CardView.java:69)
at android.support.v7.widget.CardView.<init>(CardView.java:60)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
at org.jetbrains.android.uipreview.ViewLoader.createNewInstance(ViewLoader.java:375)
at org.jetbrains.android.uipreview.ViewLoader.loadView(ViewLoader.java:100)
at com.android.tools.idea.rendering.LayoutlibCallback.loadView(LayoutlibCallback.java:172)
at android.view.BridgeInflater.loadCustomView(BridgeInflater.java:207)
at android.view.BridgeInflater.createViewFromTag(BridgeInflater.java:132)
at android.view.LayoutInflater.inflate(LayoutInflater.java:478)
at android.view.LayoutInflater.inflate(LayoutInflater.java:381)
at com.android.layoutlib.bridge.impl.RenderSessionImpl.inflate(RenderSessionImpl.java:395)
at com.android.layoutlib.bridge.Bridge.createSession(Bridge.java:329)
at com.android.ide.common.rendering.LayoutLibrary.createSession(LayoutLibrary.java:332)
at com.android.tools.idea.rendering.RenderService$3.compute(RenderService.java:575)
at com.android.tools.idea.rendering.RenderService$3.compute(RenderService.java:564)
at com.intellij.openapi.application.impl.ApplicationImpl.runReadAction(ApplicationImpl.java:932)
at com.android.tools.idea.rendering.RenderService.createRenderSession(RenderService.java:564)
at com.android.tools.idea.rendering.RenderService.render(RenderService.java:691)
at org.jetbrains.android.uipreview.AndroidLayoutPreviewToolWindowManager.doRender(AndroidLayoutPreviewToolWindowManager.java:586)
at org.jetbrains.android.uipreview.AndroidLayoutPreviewToolWindowManager.access$1900(AndroidLayoutPreviewToolWindowManager.java:80)
at org.jetbrains.android.uipreview.AndroidLayoutPreviewToolWindowManager$6$1.run(AndroidLayoutPreviewToolWindowManager.java:528)
at com.intellij.openapi.progress.impl.ProgressManagerImpl$2.run(ProgressManagerImpl.java:178)
at com.intellij.openapi.progress.ProgressManager.executeProcessUnderProgress(ProgressManager.java:209)
at com.intellij.openapi.progress.impl.ProgressManagerImpl.executeProcessUnderProgress(ProgressManagerImpl.java:212)
at com.intellij.openapi.progress.impl.ProgressManagerImpl.runProcess(ProgressManagerImpl.java:171)
at org.jetbrains.android.uipreview.AndroidLayoutPreviewToolWindowManager$6.run(AndroidLayoutPreviewToolWindowManager.java:523)
at com.intellij.util.ui.update.MergingUpdateQueue.execute(MergingUpdateQueue.java:320)
at com.intellij.util.ui.update.MergingUpdateQueue.execute(MergingUpdateQueue.java:310)
at com.intellij.util.ui.update.MergingUpdateQueue$2.run(MergingUpdateQueue.java:254)
at com.intellij.util.ui.update.MergingUpdateQueue.flush(MergingUpdateQueue.java:269)
at com.intellij.util.ui.update.MergingUpdateQueue.flush(MergingUpdateQueue.java:227)
at com.intellij.util.ui.update.MergingUpdateQueue.run(MergingUpdateQueue.java:217)
at com.intellij.util.concurrency.QueueProcessor.runSafely(QueueProcessor.java:238)
at com.intellij.util.Alarm$Request$1.run(Alarm.java:327)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334)
at java.util.concurrent.FutureTask.run(FutureTask.java:166)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:724)

这里是与 RecyclerView 相关的异常:

java.lang.NullPointerException
at android.support.v7.widget.RecyclerView.onMeasure(RecyclerView.java:1310)
at android.view.View.measure(View.java:16987)
at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:722)
at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:458)
at android.view.View.measure(View.java:16987)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5257)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:314)
at android.view.View.measure(View.java:16987)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5257)
at com.android.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:447)
at android.view.View.measure(View.java:16987)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5257)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436)
at android.widget.LinearLayout.measureHorizontal(LinearLayout.java:1083)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:615)
at android.view.View.measure(View.java:16987)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5257)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:722)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:613)
at android.view.View.measure(View.java:16987)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:875)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:613)
at android.view.View.measure(View.java:16987)
at com.android.layoutlib.bridge.impl.RenderSessionImpl.measureView(RenderSessionImpl.java:621)
at com.android.layoutlib.bridge.impl.RenderSessionImpl.render(RenderSessionImpl.java:521)
at com.android.layoutlib.bridge.Bridge.createSession(Bridge.java:331)
at com.android.ide.common.rendering.LayoutLibrary.createSession(LayoutLibrary.java:332)
at com.android.tools.idea.rendering.RenderService$3.compute(RenderService.java:575)
at com.android.tools.idea.rendering.RenderService$3.compute(RenderService.java:564)
at com.intellij.openapi.application.impl.ApplicationImpl.runReadAction(ApplicationImpl.java:932)
at com.android.tools.idea.rendering.RenderService.createRenderSession(RenderService.java:564)
at com.android.tools.idea.rendering.RenderService.render(RenderService.java:691)
at org.jetbrains.android.uipreview.AndroidLayoutPreviewToolWindowManager.doRender(AndroidLayoutPreviewToolWindowManager.java:586)
at org.jetbrains.android.uipreview.AndroidLayoutPreviewToolWindowManager.access$1900(AndroidLayoutPreviewToolWindowManager.java:80)
at org.jetbrains.android.uipreview.AndroidLayoutPreviewToolWindowManager$6$1.run(AndroidLayoutPreviewToolWindowManager.java:528)
at com.intellij.openapi.progress.impl.ProgressManagerImpl$2.run(ProgressManagerImpl.java:178)
at com.intellij.openapi.progress.ProgressManager.executeProcessUnderProgress(ProgressManager.java:209)
at com.intellij.openapi.progress.impl.ProgressManagerImpl.executeProcessUnderProgress(ProgressManagerImpl.java:212)
at com.intellij.openapi.progress.impl.ProgressManagerImpl.runProcess(ProgressManagerImpl.java:171)
at org.jetbrains.android.uipreview.AndroidLayoutPreviewToolWindowManager$6.run(AndroidLayoutPreviewToolWindowManager.java:523)
at com.intellij.util.ui.update.MergingUpdateQueue.execute(MergingUpdateQueue.java:320)
at com.intellij.util.ui.update.MergingUpdateQueue.execute(MergingUpdateQueue.java:310)
at com.intellij.util.ui.update.MergingUpdateQueue$2.run(MergingUpdateQueue.java:254)
at com.intellij.util.ui.update.MergingUpdateQueue.flush(MergingUpdateQueue.java:269)
at com.intellij.util.ui.update.MergingUpdateQueue.flush(MergingUpdateQueue.java:227)
at com.intellij.util.ui.update.MergingUpdateQueue.run(MergingUpdateQueue.java:217)
at com.intellij.util.concurrency.QueueProcessor.runSafely(QueueProcessor.java:238)
at com.intellij.util.Alarm$Request$1.run(Alarm.java:327)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334)
at java.util.concurrent.FutureTask.run(FutureTask.java:166)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:724)

这使得使用这两个（惊人的）View之一来构建布局变得几乎不可能，而我最感兴趣的恰恰是它们。

已经有解决方法了吗？或者由于它们在某种程度上是“自定义”View，这实际上是预期行为吗？

- tolgap

---

今天早些时候，我记得有人问过关于CardView.Dark的问题。 - CommonsWare

问题是，我没有在任何地方提到“Dark”主题。我只是声明了android.support.v7.widget.CardView标签。没有“Dark”（可能是默认主题）。@CommonsWare，你有遇到过这个问题吗？ - tolgap

我还没有尝试过。我只记得今天早些时候在SO上看到过类似这样的问题提及。 - CommonsWare

Answer 1

这是Android Studio中的一个漏洞。预览工具不知道如何初始化小部件。我认为是这样，因为如果在您的代码中忘记调用recyclerView.setLayoutManager（），则会从您的应用程序中抛出相同的异常。

- user7610

---

你说得对，我刚刚遇到了这个链接。Android Studio 似乎在2小时前更新了。 - tolgap

我已经安装了更新，但是RecyclerView仍然无法在预览中显示。相反，它至少显示了更有意义的错误信息：“新的RecyclerView在Studio中尚未工作。我们正在努力修复。(打开问题72117，显示异常)” https://code.google.com/p/android/issues/detail?id=72117 - user7610

CardView 的 bug 报告似乎是这个：https://code.google.com/p/android/issues/detail?id=79071，该报告还链接到 Android Studio 中的此更改：https://android-review.googlesource.com/#/c/113416/ - personne3000

Answer 2

我正在使用Eclipse并遇到了相同的问题。如用户7610所建议，您需要调用recyclerView.setLayoutManager()来解决这个问题。

以下是我的解决方法...

创建一个成员变量...

RecyclerView.LayoutManager mLayoutManager;

在 onCreate() 或 onCreateView() 中。

recyclerView = (RecyclerView) view
                .findViewById(R.id.business_recycler_view);
recyclerView.setHasFixedSize(true);

mLayoutManager = new LinearLayoutManager(getActivity());
recyclerView.setLayoutManager(mLayoutManager);

这解决了我的NullPointerException问题。

- Vamsi Challa

---

感谢详细的解释。 - Yasitha Waduge

Answer 3

我发现了相似的问题。 如果我们只充气包含RecyclerView的布局，那么在设置contentView时会出错，因为在布局文件中未定义RecyclerView的布局管理器。

RecyclerView recyclerView = (RecyclerView) findViewById(R.id.searchResultsList);
LinearLayoutManager layoutmanager = new LinearLayoutManager(this);
layoutmanager.setOrientation(LinearLayoutManager.VERTICAL);
recyclerView.setLayoutManager(layoutmanager);

- Ronak Poriya

Answer 4

如果有人在片段中使用Recycler视图遇到相同的问题，请使用此代码。

@Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View rootView = inflater.inflate(R.layout.fragment_timeline, container, false);

        mRecyclerView = (RecyclerView) rootView.findViewById(R.id.my_recycler_view);

        // use this setting to improve performance if you know that changes
        // in content do not change the layout size of the RecyclerView

        mRecyclerView.setHasFixedSize(true);
        // use a linear layout manager
        mLayoutManager = new LinearLayoutManager(getActivity());
        mRecyclerView.setLayoutManager(mLayoutManager);


        String[] abc = {"hi","how are you","this is recycler"};
        // specify an adapter (see also next example)
        mAdapter = new RecyclerViewAdapter(abc);
        mRecyclerView.setAdapter(mAdapter);
        return rootView;
    }

- sanath_p