activity_main.xml: java.lang.NullPointerException[通俗易懂]

1、错误描写叙述

eclipse.buildId=4.4.0.I20140606-1215 java.version=1.7.0_67 java.vendor=Oracle Corporation BootLoader constants: OS=win32, ARCH=x86_64, WS=win32, NL=zh_CN Framework arguments: -product org.eclipse.epp.package.jee.product Command-line arguments: -os win32 -ws win32 -arch x86_64 -product org.eclipse.epp.package.jee.product com.android.ide.eclipse.adt Error Fri Jun 05 23:50:22 CST 2015 activity_main.xml: java.lang.NullPointerException java.lang.NullPointerException at android.support.v7.internal.widget.ActionBarOverlayLayout.getDecorToolbar(ActionBarOverlayLayout.java:599) at android.support.v7.internal.widget.ActionBarOverlayLayout.pullChildren(ActionBarOverlayLayout.java:588) at android.support.v7.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:359) at android.view.View.measure(View.java:17547) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535) 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:17547) at android.widget.LinearLayout.measureVertical(LinearLayout.java:875) at android.widget.LinearLayout.onMeasure(LinearLayout.java:613) at android.view.View.measure(View.java:17547) at com.android.layoutlib.bridge.impl.RenderSessionImpl.measureView(RenderSessionImpl.java:640) at com.android.layoutlib.bridge.impl.RenderSessionImpl.render(RenderSessionImpl.java:540) at com.android.layoutlib.bridge.Bridge.createSession(Bridge.java:323) at com.android.ide.common.rendering.LayoutLibrary.createSession(LayoutLibrary.java:349) at com.android.ide.eclipse.adt.internal.editors.layout.gle2.RenderService.createRenderSession(RenderService.java:519) at com.android.ide.eclipse.adt.internal.editors.layout.gle2.GraphicalEditorPart.renderWithBridge(GraphicalEditorPart.java:1584) at com.android.ide.eclipse.adt.internal.editors.layout.gle2.GraphicalEditorPart.recomputeLayout(GraphicalEditorPart.java:1309) at com.android.ide.eclipse.adt.internal.editors.layout.gle2.GraphicalEditorPart.activated(GraphicalEditorPart.java:1066) at com.android.ide.eclipse.adt.internal.editors.layout.LayoutEditorDelegate.delegatePageChange(LayoutEditorDelegate.java:686) at com.android.ide.eclipse.adt.internal.editors.common.CommonXmlEditor.pageChange(CommonXmlEditor.java:360) at org.eclipse.ui.part.MultiPageEditorPart.setActivePage(MultiPageEditorPart.java:1101) at org.eclipse.ui.forms.editor.FormEditor.setActivePage(FormEditor.java:607) at com.android.ide.eclipse.adt.internal.editors.AndroidXmlEditor.selectDefaultPage(AndroidXmlEditor.java:450) at com.android.ide.eclipse.adt.internal.editors.AndroidXmlEditor.addPages(AndroidXmlEditor.java:311) at com.android.ide.eclipse.adt.internal.editors.common.CommonXmlEditor.addPages(CommonXmlEditor.java:285) at org.eclipse.ui.forms.editor.FormEditor.createPages(FormEditor.java:138) at org.eclipse.ui.part.MultiPageEditorPart.createPartControl(MultiPageEditorPart.java:362) at org.eclipse.ui.internal.e4.compatibility.CompatibilityPart.createPartControl(CompatibilityPart.java:140) at org.eclipse.ui.internal.e4.compatibility.CompatibilityEditor.createPartControl(CompatibilityEditor.java:99) at org.eclipse.ui.internal.e4.compatibility.CompatibilityPart.create(CompatibilityPart.java:321) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:606) at org.eclipse.e4.core.internal.di.MethodRequestor.execute(MethodRequestor.java:55) at org.eclipse.e4.core.internal.di.InjectorImpl.processAnnotated(InjectorImpl.java:888) at org.eclipse.e4.core.internal.di.InjectorImpl.processAnnotated(InjectorImpl.java:869) at org.eclipse.e4.core.internal.di.InjectorImpl.inject(InjectorImpl.java:120) at org.eclipse.e4.core.internal.di.InjectorImpl.internalMake(InjectorImpl.java:337) at org.eclipse.e4.core.internal.di.InjectorImpl.make(InjectorImpl.java:258) at org.eclipse.e4.core.contexts.ContextInjectionFactory.make(ContextInjectionFactory.java:162) at org.eclipse.e4.ui.internal.workbench.ReflectionContributionFactory.createFromBundle(ReflectionContributionFactory.java:104) at org.eclipse.e4.ui.internal.workbench.ReflectionContributionFactory.doCreate(ReflectionContributionFactory.java:73) at org.eclipse.e4.ui.internal.workbench.ReflectionContributionFactory.create(ReflectionContributionFactory.java:55) at org.eclipse.e4.ui.workbench.renderers.swt.ContributedPartRenderer.createWidget(ContributedPartRenderer.java:127) at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.createWidget(PartRenderingEngine.java:983) at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:662) at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:766) at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.access$2(PartRenderingEngine.java:737) at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$7.run(PartRenderingEngine.java:731) at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42) at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.createGui(PartRenderingEngine.java:715) at org.eclipse.e4.ui.workbench.renderers.swt.StackRenderer.showTab(StackRenderer.java:1251) at org.eclipse.e4.ui.workbench.renderers.swt.LazyStackRenderer$1.handleEvent(LazyStackRenderer.java:66) at org.eclipse.e4.ui.services.internal.events.UIEventHandler$1.run(UIEventHandler.java:40) at org.eclipse.swt.widgets.Synchronizer.syncExec(Synchronizer.java:187) at org.eclipse.ui.internal.UISynchronizer.syncExec(UISynchronizer.java:156) at org.eclipse.swt.widgets.Display.syncExec(Display.java:4734) at org.eclipse.e4.ui.internal.workbench.swt.E4Application$1.syncExec(E4Application.java:218) at org.eclipse.e4.ui.services.internal.events.UIEventHandler.handleEvent(UIEventHandler.java:36) at org.eclipse.equinox.internal.event.EventHandlerWrapper.handleEvent(EventHandlerWrapper.java:197) at org.eclipse.equinox.internal.event.EventHandlerTracker.dispatchEvent(EventHandlerTracker.java:197) at org.eclipse.equinox.internal.event.EventHandlerTracker.dispatchEvent(EventHandlerTracker.java:1) at org.eclipse.osgi.framework.eventmgr.EventManager.dispatchEvent(EventManager.java:230) at org.eclipse.osgi.framework.eventmgr.ListenerQueue.dispatchEventSynchronous(ListenerQueue.java:148) at org.eclipse.equinox.internal.event.EventAdminImpl.dispatchEvent(EventAdminImpl.java:135) at org.eclipse.equinox.internal.event.EventAdminImpl.sendEvent(EventAdminImpl.java:78) at org.eclipse.equinox.internal.event.EventComponent.sendEvent(EventComponent.java:39) at org.eclipse.e4.ui.services.internal.events.EventBroker.send(EventBroker.java:81) at org.eclipse.e4.ui.internal.workbench.UIEventPublisher.notifyChanged(UIEventPublisher.java:59) at org.eclipse.emf.common.notify.impl.BasicNotifierImpl.eNotify(BasicNotifierImpl.java:374) at org.eclipse.e4.ui.model.application.ui.impl.ElementContainerImpl.setSelectedElement(ElementContainerImpl.java:171) at org.eclipse.e4.ui.internal.workbench.ModelServiceImpl.showElementInWindow(ModelServiceImpl.java:488) at org.eclipse.e4.ui.internal.workbench.ModelServiceImpl.bringToTop(ModelServiceImpl.java:454) at org.eclipse.e4.ui.internal.workbench.PartServiceImpl.delegateBringToTop(PartServiceImpl.java:692) at org.eclipse.e4.ui.internal.workbench.PartServiceImpl.bringToTop(PartServiceImpl.java:385) at org.eclipse.e4.ui.internal.workbench.PartServiceImpl.showPart(PartServiceImpl.java:1126) at org.eclipse.ui.internal.WorkbenchPage.busyOpenEditor(WorkbenchPage.java:3182) at org.eclipse.ui.internal.WorkbenchPage.access$23(WorkbenchPage.java:3104) at org.eclipse.ui.internal.WorkbenchPage$9.run(WorkbenchPage.java:3086) at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:70) at org.eclipse.ui.internal.WorkbenchPage.openEditor(WorkbenchPage.java:3081) at org.eclipse.ui.internal.WorkbenchPage.openEditor(WorkbenchPage.java:3045) at org.eclipse.ui.internal.WorkbenchPage.openEditor(WorkbenchPage.java:3035) at org.eclipse.ui.ide.IDE.openEditor(IDE.java:541) at org.eclipse.ui.ide.IDE.openEditor(IDE.java:500) at org.eclipse.jdt.internal.ui.javaeditor.EditorUtility.openInEditor(EditorUtility.java:360) at org.eclipse.jdt.internal.ui.javaeditor.EditorUtility.openInEditor(EditorUtility.java:167) at org.eclipse.jdt.ui.actions.OpenAction.run(OpenAction.java:268) at org.eclipse.jdt.ui.actions.OpenAction.run(OpenAction.java:233) at org.eclipse.jdt.ui.actions.SelectionDispatchAction.dispatchRun(SelectionDispatchAction.java:275) at org.eclipse.jdt.ui.actions.SelectionDispatchAction.run(SelectionDispatchAction.java:251) at org.eclipse.jdt.internal.ui.packageview.PackageExplorerActionGroup.handleOpen(PackageExplorerActionGroup.java:376) at org.eclipse.jdt.internal.ui.packageview.PackageExplorerPart$4.open(PackageExplorerPart.java:538) at org.eclipse.ui.OpenAndLinkWithEditorHelper$InternalListener.open(OpenAndLinkWithEditorHelper.java:48) at org.eclipse.jface.viewers.StructuredViewer$2.run(StructuredViewer.java:853) at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42) at org.eclipse.ui.internal.JFaceUtil$1.run(JFaceUtil.java:50) at org.eclipse.jface.util.SafeRunnable.run(SafeRunnable.java:178) at org.eclipse.jface.viewers.StructuredViewer.fireOpen(StructuredViewer.java:850) at org.eclipse.jface.viewers.StructuredViewer.handleOpen(StructuredViewer.java:1142) at org.eclipse.jface.viewers.StructuredViewer$6.handleOpen(StructuredViewer.java:1249) at org.eclipse.jface.util.OpenStrategy.fireOpenEvent(OpenStrategy.java:278) at org.eclipse.jface.util.OpenStrategy.access$2(OpenStrategy.java:272) at org.eclipse.jface.util.OpenStrategy$1.handleEvent(OpenStrategy.java:313) at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84) at org.eclipse.swt.widgets.Display.sendEvent(Display.java:4353) at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1061) at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:4172) at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3761) at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$9.run(PartRenderingEngine.java:1151) at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332) at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:1032) at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:148) at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:636) at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332) at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:579) at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:150) at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:135) at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196) at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:134) at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:104) at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:382) at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:236) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:606) at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:648) at org.eclipse.equinox.launcher.Main.basicRun(Main.java:603) at org.eclipse.equinox.launcher.Main.run(Main.java:1465) 

2、错误原因

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:paddingBottom="@dimen/activity_vertical_margin" android:paddingLeft="@dimen/activity_horizontal_margin" android:paddingRight="@dimen/activity_horizontal_margin" android:paddingTop="@dimen/activity_vertical_margin" tools:context="com.example.helloworld.MainActivity" > <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/hello_world" /> <CheckBox android:layout_width="wrap_content" android:layout_height="wrap_content"/> </RelativeLayout>

3、解决的方法