android - 加载 Android 布局 XML 文件时出现异常

Question

由于某些原因，当我在 eclipse 中加载 XML 布局时出现以下异常。

我不太确定是什么原因造成的，因为我认为我没有对该文件进行任何新的更改。此外，当我在 Eclipse 中使用 API 19 渲染布局时，也不异常(exception)。但是，当我使用 API 21 渲染时，出现以下异常？什么可能会触发这种异常？

java.lang.NullPointerException
at android.view.ViewGroup_Delegate.drawShadow(ViewGroup_Delegate.java:74)
at android.view.ViewGroup_Delegate.drawChild(ViewGroup_Delegate.java:61)
at android.view.ViewGroup.drawChild(ViewGroup.java:3404)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3198)
at android.view.View.draw(View.java:15017)
at android.view.ViewGroup.drawChild_Original(ViewGroup.java:3404)
at android.view.ViewGroup_Delegate.drawChild(ViewGroup_Delegate.java:53)
at android.view.ViewGroup.drawChild(ViewGroup.java:3404)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3198)
at android.view.View.draw(View.java:15017)
at android.view.ViewGroup.drawChild_Original(ViewGroup.java:3404)
at android.view.ViewGroup_Delegate.drawChild(ViewGroup_Delegate.java:53)
at android.view.ViewGroup.drawChild(ViewGroup.java:3404)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3198)
at android.view.View.draw(View.java:15017)
at android.view.ViewGroup.drawChild_Original(ViewGroup.java:3404)
at android.view.ViewGroup_Delegate.drawChild(ViewGroup_Delegate.java:53)
at android.view.ViewGroup.drawChild(ViewGroup.java:3404)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3198)
at android.view.View.draw(View.java:15223)
at android.widget.FrameLayout.draw(FrameLayout.java:592)
at android.widget.ScrollView.draw(ScrollView.java:1689)
at android.view.View.draw(View.java:15022)
at android.view.ViewGroup.drawChild_Original(ViewGroup.java:3404)
at android.view.ViewGroup_Delegate.drawChild(ViewGroup_Delegate.java:53)
at android.view.ViewGroup.drawChild(ViewGroup.java:3404)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3198)
at android.view.View.draw(View.java:15017)
at android.view.ViewGroup.drawChild_Original(ViewGroup.java:3404)
at android.view.ViewGroup_Delegate.drawChild(ViewGroup_Delegate.java:53)
at android.view.ViewGroup.drawChild(ViewGroup.java:3404)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3198)
at android.view.View.draw(View.java:15017)
at android.view.ViewGroup.drawChild_Original(ViewGroup.java:3404)
at android.view.ViewGroup_Delegate.drawChild(ViewGroup_Delegate.java:53)
at android.view.ViewGroup.drawChild(ViewGroup.java:3404)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3198)
at android.view.View.draw(View.java:15117)
at android.view.View.draw(View.java:15022)
at android.view.ViewGroup.drawChild_Original(ViewGroup.java:3404)
at android.view.ViewGroup_Delegate.drawChild(ViewGroup_Delegate.java:53)
at android.view.ViewGroup.drawChild(ViewGroup.java:3404)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3198)
at android.view.View.draw(View.java:15117)
at com.android.layoutlib.bridge.impl.RenderSessionImpl.render(RenderSessionImpl.java:587)
at com.android.layoutlib.bridge.Bridge.createSession(Bridge.java:334)
at com.android.ide.common.rendering.LayoutLibrary.createSession(LayoutLibrary.java:332)
at com.android.ide.eclipse.adt.internal.editors.layout.gle2.RenderService.createRenderSession(RenderService.java:517)
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$2.widgetSelected(MultiPageEditorPart.java:294)
at org.eclipse.swt.widgets.TypedListener.handleEvent(TypedListener.java:248)
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.Widget.sendEvent(Widget.java:1085)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1070)
at org.eclipse.swt.widgets.Widget.notifyListeners(Widget.java:782)
at org.eclipse.swt.custom.CTabFolder.setSelection(CTabFolder.java:3110)
at org.eclipse.swt.custom.CTabFolder.onMouse(CTabFolder.java:1794)
at org.eclipse.swt.custom.CTabFolder$1.handleEvent(CTabFolder.java:283)
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(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
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)
at org.eclipse.equinox.launcher.Main.main(Main.java:1438)

Answer 1

我在 Android Studio 中遇到了同样的问题。在我的例子中，根布局是一个 LinearLayout。在那里，我有一个嵌套的 RelativeLayout，其布局高度和宽度为 match_parent 和一个 DrawerLayout，其布局高度和宽度也为 match_parent。我在 RelativeLayout 中也有一个 Button 和 TextView。我认为 AndroidStudio 无法绘制 Button 和/或 TextView 因为所有嵌套的“match_parent”。

我会尝试查看嵌套布局。如果您的问题不是嵌套布局，我会尝试一点一点地改变您的布局，看看 IDE 无法呈现的内容。