问题
So I've been taking a shot at the Material Design of Android Preview L. I imported both the CardView and the RecyclerView libraries.
I use the Android Studio preview version 0.8.0. Have the latest SDK packages installed.
Once I use them in my layout files though, the previewer throws an exception for both of them.
Here is the exception for the CardView:
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)
And here is the exception for RecyclerView:
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)
This makes building layout near impossible using these two (amazing) Views, which I'm most curious about.
Is there a fix for this already, or is this actually expected behaviour seeing as they're "custom" Views, in a sense?
回答1:
This is a bug in Android Studio. The preview tool does not know how do initialize the widgets. I believe so, because the same exception is thrown from your app if you forget to call recyclerView.setLayoutManager() in your code.
回答2:
I am using Eclipse and faced the same issue. As suggested by user7610, you need to call recyclerView.setLayoutManager() to get over this.
Here is how i solved it..
Create a member variable..
RecyclerView.LayoutManager mLayoutManager;
In onCreate() or onCreateView()
recyclerView = (RecyclerView) view
.findViewById(R.id.business_recycler_view);
recyclerView.setHasFixedSize(true);
mLayoutManager = new LinearLayoutManager(getActivity());
recyclerView.setLayoutManager(mLayoutManager);
This solved my NullPointerException.
回答3:
I found Similar Issue. As such if we only inflate layout which consist RecyclerView then While doing setcontentView it gives error because layout manager is not set for Recyclerview Defined in Layout file.
RecyclerView recyclerView = (RecyclerView) findViewById(R.id.searchResultsList);
LinearLayoutManager layoutmanager = new LinearLayoutManager(this);
layoutmanager.setOrientation(LinearLayoutManager.VERTICAL);
recyclerView.setLayoutManager(layoutmanager);
回答4:
If some one is facing the same issue for Recycler view inside fragment use this code
@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;
}
来源：https://stackoverflow.com/questions/24458538/using-cardview-and-recyclerview-in-my-layout-files-throws-an-exception