Android Studio预览抽屉菜单布局时出现空指针异常求助

我看到你在创建包含Drawer Layout的新项目后，在预览面板查看抽屉导航时遇到了空指针错误，先把错误日志整理出来方便定位：

null java.lang.NullPointerException 
at com.android.tools.idea.uibuilder.scene.LayoutlibSceneManager.getRenderResult(LayoutlibSceneManager.java:602) 
at com.android.tools.idea.uibuilder.surface.ScreenViewBase.getResult(ScreenViewBase.java:109) 
at com.android.tools.idea.uibuilder.surface.ScreenView.getResult(ScreenView.java:30) 
at com.android.tools.idea.uibuilder.menu.NavigationViewSceneView.getPreferredSize(NavigationViewSceneView.java:64) 
at com.android.tools.idea.common.surface.SceneView.getPreferredSize(SceneView.java:95) 
at com.android.tools.idea.uibuilder.scene.LayoutlibSceneManager.createSceneViewsForMenu(LayoutlibSceneManager.java:265) 
at com.android.tools.idea.uibuilder.scene.LayoutlibSceneManager.doCreateSceneView(LayoutlibSceneManager.java:234) 
at com.android.tools.idea.common.scene.SceneManager.createSceneView(SceneManager.java:73) 
at com.android.tools.idea.common.scene.SceneManager.<init>(SceneManager.java:66) 
at com.android.tools.idea.uibuilder.scene.LayoutlibSceneManager.<init>(LayoutlibSceneManager.java:157) 
at com.android.tools.idea.uibuilder.surface.NlDesignSurface.createSceneManager(NlDesignSurface.java:145) 
at com.android.tools.idea.common.surface.DesignSurface.setModel(DesignSurface.java:281) 
at com.android.tools.idea.common.editor.NlEditorPanel.initNeleModelOnEventDispatchThread(NlEditorPanel.java:143) 
at com.android.tools.idea.common.editor.NlEditorPanel.lambda$null$4(NlEditorPanel.java:139) 
at com.intellij.openapi.project.DumbServiceImpl.lambda$smartInvokeLater$7(DumbServiceImpl.java:366) 
at com.intellij.openapi.application.TransactionGuardImpl$2.run(TransactionGuardImpl.java:315) 
at com.intellij.openapi.application.impl.LaterInvocator$FlushQueue.runNextEvent(LaterInvocator.java:424) 
at com.intellij.openapi.application.impl.LaterInvocator$FlushQueue.run(LaterInvocator.java:407) 
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311) 
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:762) 
at java.awt.EventQueue.access$500(EventQueue.java:98) 
at java.awt.EventQueue$3.run(EventQueue.java:715) 
at java.awt.EventQueue$3.run(EventQueue.java:709) 
at java.security.AccessController.doPrivileged(Native Method) 
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80) 
at java.awt.EventQueue.dispatchEvent(EventQueue.java:732) 
at com.intellij.ide.IdeEventQueue.defaultDispatchEvent(IdeEventQueue.java:822) 
at com.intellij.ide.IdeEventQueue._dispatchEvent(IdeEventQueue.java:650) 
at com.intellij.ide.IdeEventQueue.dispatchEvent(IdeEventQueue.java:366) 
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201) 
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116) 
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105) 
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101) 
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93) 
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82) 
java.lang.NullPointerException 
at com.android.tools.idea.uibuilder.scene.LayoutlibSceneManager.getRenderResult(LayoutlibSceneManager.java:602) 
at com.android.tools.idea.uibuilder.surface.ScreenViewBase.getResult(ScreenViewBase.java:109) 
at com.android.tools.idea.uibuilder.surface.ScreenView.getResult(ScreenView.java:30) 
at com.android.tools.idea.uibuilder.menu.NavigationViewSceneView.getPreferredSize(NavigationViewSceneView.java:64) 
at com.android.tools.idea.common.surface.SceneView.getPreferredSize(SceneView.java:95) 
at com.android.tools.idea.uibuilder.scene.LayoutlibSceneManager.createSceneViewsForMenu(LayoutlibSceneManager.java:265) 
at com.android.tools.idea.uibuilder.scene.LayoutlibSceneManager.doCreateSceneView(LayoutlibSceneManager.java:234) 
at com.android.tools.idea.common.scene.SceneManager.createSceneView(SceneManager.java:73) 
at com.android.tools.idea.common.scene.SceneManager.<init>(SceneManager.java:66) 
at com.android.tools.idea.uibuilder.scene.LayoutlibSceneManager.<init>(LayoutlibSceneManager.java:157) 
at com.android.tools.idea.uibuilder.surface.NlDesignSurface.createSceneManager(NlDesignSurface.java:145) 
at com.android.tools.idea.common.surface.DesignSurface.setModel(DesignSurface.java:281) 
at com.android.tools.idea.uibuilder.editor.NlPreviewForm.initNeleModel(NlPreviewForm.java:420) 
at com.android.tools.idea.uibuilder.editor.NlPreviewForm.initPreviewForm(NlPreviewForm.java:309) 
at com.android.tools.idea.uibuilder.editor.NlPreviewForm.setNextEditor(NlPreviewForm.java:289) 
at com.android.tools.idea.uibuilder.editor.NlPreviewManager$2.run(NlPreviewManager.java)

实用解决步骤 #

我之前也碰到过类似的预览面板异常，试试下面这些方法，大概率能解决问题：

• 检查NavigationView的资源配置：这个空指针很多时候是因为NavigationView的app:menu或app:headerLayout属性指向了不存在的资源。打开你的布局文件，确认菜单文件确实在res/menu目录下，header布局文件也在res/layout里，路径拼写完全正确。

• 清理重建项目：Android Studio的缓存偶尔会搞出奇怪的问题。点击顶部菜单栏的Build -> Clean Project，等清理完成后再选Rebuild Project，构建结束后重新打开预览面板试试。

• 更新Android Studio版本：这个错误可能是IDE的已知bug，旧版本的Android Studio在处理Drawer Layout预览时容易出问题。检查一下Help -> Check for Updates，更新到最新稳定版后再尝试。

• 切换预览API版本：如果预览面板使用的API版本和项目的targetSDK不匹配，也可能触发异常。在预览面板顶部的API选择器里，切换到和你项目targetSDK一致的版本，或者试试更高的API版本。

• 禁用Instant Run：虽然这个功能现在已经逐步被弃用，但如果你的IDE还开启着它，可能会干扰预览。到File -> Settings -> Build, Execution, Deployment -> Instant Run里关掉它，然后重启IDE。

如果上面的方法都没用，你可以创建一个全新的Drawer Layout模板项目，对比一下两个项目的布局文件和资源配置，看看是不是自己的项目里哪里配置漏了或错了。

内容的提问来源于stack exchange，提问作者user5327287