尝试打开 Android XML 视图时 Eclipse 中抛出 NullPointerException？

Question

这里是一个例外：

java.lang.NullPointerException
at android.widget.TextView.setTextColor(TextView.java:1787)
at android.widget.TabHost$LabelIndicatorStrategy.createIndicatorView(TabHost.java:521)
at android.widget.TabHost.addTab(TabHost.java:204)
at com.android.layoutlib.bridge.Bridge.setupTabHost(Bridge.java:880)
at com.android.layoutlib.bridge.Bridge.postInflateProcess(Bridge.java:807)
at com.android.layoutlib.bridge.Bridge.postInflateProcess(Bridge.java:813)
at com.android.layoutlib.bridge.Bridge.computeLayout(Bridge.java:401)
at com.android.ide.eclipse.adt.internal.editors.layout.gle2.GraphicalEditorPart.computeLayout(Unknown Source)
at com.android.ide.eclipse.adt.internal.editors.layout.gle2.GraphicalEditorPart.renderWithBridge(Unknown Source)
at com.android.ide.eclipse.adt.internal.editors.layout.gle2.GraphicalEditorPart.recomputeLayout(Unknown Source)
at com.android.ide.eclipse.adt.internal.editors.layout.gle2.GraphicalEditorPart.activated(Unknown Source)
at com.android.ide.eclipse.adt.internal.editors.layout.LayoutEditor.pageChange(Unknown Source)
at org.eclipse.ui.part.MultiPageEditorPart$2.widgetSelected(MultiPageEditorPart.java:290)
at org.eclipse.swt.widgets.TypedListener.handleEvent(TypedListener.java:234)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1258)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1282)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1267)
at org.eclipse.swt.widgets.Widget.notifyListeners(Widget.java:1061)
at org.eclipse.swt.custom.CTabFolder.setSelection(CTabFolder.java:2743)
at org.eclipse.swt.custom.CTabFolder.onMouse(CTabFolder.java:1429)
at org.eclipse.swt.custom.CTabFolder$1.handleEvent(CTabFolder.java:257)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1258)
at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:3540)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3161)
at org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.java:2640)
at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:2604)
at org.eclipse.ui.internal.Workbench.access$4(Workbench.java:2438)
at org.eclipse.ui.internal.Workbench$7.run(Workbench.java:671)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:664)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149)
at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:115)
at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:369)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:179)
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:616)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:619)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:574)
at org.eclipse.equinox.launcher.Main.run(Main.java:1407)

这是与之关联的 main.xml 文件：

<?xml version="1.0" encoding="utf-8"?>
<TabHost
  xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"
  android:id="@android:id/tabhost">

  <LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:padding="5dp">
  <TabWidget 
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:id="@android:id/tabs" />
    <FrameLayout
        android:id="@android:id/tabcontent"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent">

        <include layout="@layout/basic_tab" />
        <include layout="@layout/advanced_tab" />

    </FrameLayout>
  </LinearLayout>
</TabHost>

两个包含文件单独工作都很好。但在选项卡布局中时，会发生此错误。有修复吗？
这是代码：

import android.app.TabActivity;
import android.content.res.Resources;
import android.os.Bundle;
import android.widget.TabHost;

import com.mohit.geo2do.R;

public class TaskEdit extends TabActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.edit_task);

        Resources res = getResources();
        TabHost host = getTabHost();

        host.addTab(host.newTabSpec("basic")
            .setIndicator("Basic", res.getDrawable(android.R.drawable.ic_menu_edit))
            .setContent(R.layout.basic_tab));
        host.addTab(host.newTabSpec("advanced")
            .setIndicator("Advanced", res.getDrawable(android.R.drawable.ic_menu_manage))
            .setContent(R.layout.advanced_tab));

        host.setCurrentTab(0);
    }
}

这里是 xml 文件，advanced_tab:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"
  android:orientation="vertical"
  android:id="@+id/advanced_tab_layout">

  <TextView 
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentTop="true" 
    android:text="Notify me:"
    android:textColor="#FFFFFF"
    android:textStyle="bold" 
  />

  <CheckBox 
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       android:layout_alignParentTop="true"
       android:id="@+id/task_due" 
       android:text="when task is due"
       android:textColor="#FFFFFF"
       android:textStyle="bold" 
       android:paddingTop="5dip"
   />

   <CheckBox 
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       android:layout_alignParentTop="true"
       android:id="@+id/task_overdue" 
       android:text="when task is overdue"
       android:textColor="#FFFFFF"
       android:textStyle="bold" 
       android:paddingTop="5dip"
   /> 

   <CheckBox 
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       android:layout_alignParentTop="true"
       android:id="@+id/task_datetime" 
       android:text="at"
       android:textColor="#FFFFFF"
       android:textStyle="bold" 
       android:paddingTop="5dip"
   />

   <TextView 
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentTop="true" 
    android:text="Calendar:"
    android:textColor="#FFFFFF"
    android:textStyle="bold" 
    android:paddingTop="5dip"
    />

   <CheckBox 
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       android:layout_alignParentTop="true"
       android:id="@+id/task_calendar" 
       android:text="Create a calendar event"
       android:textColor="#FFFFFF"
       android:textStyle="bold" 
       android:paddingTop="5dip"
   />

</LinearLayout>

和 basic_tab.xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent" 
android:layout_height="fill_parent"
android:orientation="vertical"
android:id="@+id/basic_tab_layout">
<TextView 
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_alignParentTop="true"
   android:text="Title:"
   android:textColor="#FFFFFF"
   android:textStyle="bold" 
   android:paddingTop="5dip"
/>

<EditText
   android:layout_width="fill_parent"
   android:layout_height="wrap_content"
   android:id="@+id/title"
   android:hint="Name of the task..."
/>  

<TextView
   android:layout_height="wrap_content"
   android:layout_width="wrap_content"
   android:text="Importance:"
   android:textColor="#FFFFFF"
   android:textStyle="bold"
   android:paddingTop="10dip"
/>

<RadioGroup 
    android:layout_height="wrap_content"
    android:layout_width="fill_parent"
    android:orientation="horizontal"
    android:id="@+id/importance_grp">

    <RadioButton
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="High" 
        android:paddingRight="25dip"
    />
    <RadioButton
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Medium" 
        android:checked="true"
        android:paddingRight="25dip"
    />
    <RadioButton
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Low" 
    />

</RadioGroup>

<TextView
   android:layout_height="wrap_content"
   android:layout_width="wrap_content"
   android:text="Due Date:"
   android:textColor="#FFFFFF"
   android:textStyle="bold"
   android:paddingTop="10dip"
/>

<Spinner
   android:layout_width="fill_parent"
   android:layout_height="wrap_content"
   android:id="@+id/due_date" 
   android:prompt="@string/due_date_prompt"
   android:entries="@array/due_date_entries"
/>

    <TextView
       android:layout_height="wrap_content"
       android:layout_width="wrap_content"
       android:text="Notes:"
       android:textColor="#FFFFFF"
       android:textStyle="bold"
       android:paddingTop="10dip"
    />

    <EditText
        android:layout_height="wrap_content"
        android:layout_width="fill_parent"
        android:id="@+id/notes"
        android:hint="Notes..."
        android:minLines="4" 
    />

</LinearLayout>

更新：

显然：

host.addTab(host.newTabSpec("advanced")
        .setIndicator("Advanced", res.getDrawable(android.R.drawable.ic_menu_manage))
        .setContent(R.layout.advanced_tab));

不采用布局 xml 文件作为其内容。它应该是：

host.addTab(host.newTabSpec("advanced")
        .setIndicator("Advanced", res.getDrawable(android.R.drawable.ic_menu_manage))
        .setContent(R.id.advanced_tab_layout));

其中 setContent 采用 id。我仍然收到该错误，但在模拟器上，选项卡实际上显示，但没有内容！

Answer 1

您列出的例外是布局编辑器本身的错误。运行 Android 布局代码时，我们没有正确初始化 SDK 版本，这意味着 TabWidget 中的一些版本条件代码将会运行（这会失败，因为它实际上并未在它认为的版本中运行）。我们正在 ADT 10 中修复此问题（以及选项卡的各种其他渲染/预览问题。）

(这是查找正确版本以传递给渲染器的变更集）

Answer 2

好吧，我刚刚清理了项目并删除了 edit_task.xml 文件并重新创建了它。现在效果很好。

Answer 3

最后有一个解决方法，安装Android 3.0 Preview SDK，可以将布局编辑器中的Render Target设置为3.0。

更多信息请点击这里-> http://code.google.com/p/android/issues/detail ?id=13092