Tabhost空指针异常

本文介绍了Tabhost空指针异常的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

能否有人请帮助我TabHost的这个例子吗？我的问题是，当我试图运行应用程序我得到空指针异常。

Can some one please assist me in this example of TabHost? The problem i have is, When I am trying to run the application I am getting Null Pointer Exception.

下面是code。如果有人需要去看看。

Here is the code if some one need to have a look.

public class TabBarExample extends Activity { /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); /** * TabHost will have Tabs **/ TabHost tabHost = (TabHost)findViewById(android.R.id.tabhost); /** TabSpec used to create a new tab. * By using TabSpec only we can able to setContent to the tab. * By using TabSpec setIndicator() we can set name to tab. **/ TabHost.TabSpec spec1, spec2; spec1 = tabHost.newTabSpec("tab_id_1").setIndicator("Tab One").setContent(new Intent().setClass(this, FirstTab.class)); spec2 = tabHost.newTabSpec("tab_id_2").setIndicator("Tab Two").setContent(new Intent().setClass(this, SecondTab.class)); /** * create intent of each tab pressed **/ //Intent intent1 = new Intent().setClass(this, FirstTab.class); //Intent intent2 = new Intent().setClass(this, SecondTab.class); /** * add the created tab to the tab host for display **/ // I am getting error at the following line tabHost.addTab(spec1); tabHost.addTab(spec2); } }

中的任何一个，以协助以任何方式或指向我一个方向将是AP preciated。问候设拉子

Any one to assist in any way or point me to a direction will be appreciated. Regards Shiraz

EDIT--这里是我得到的错误的LogCat中查看

EDIT-- here is the LogCat view of the error i am getting

06-18 23:18:30.547: ERROR/AndroidRuntime(1404): FATAL EXCEPTION: main 06-18 23:18:30.547: ERROR/AndroidRuntime(1404): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.moonlight.tabbarexample/com.moonlight.tabbarexample.TabBarExample}: java.lang.NullPointerException 06-18 23:18:30.547: ERROR/AndroidRuntime(1404): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1816) 06-18 23:18:30.547: ERROR/AndroidRuntime(1404): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1837) 06-18 23:18:30.547: ERROR/AndroidRuntime(1404): at android.app.ActivityThread.access$1500(ActivityThread.java:132) 06-18 23:18:30.547: ERROR/AndroidRuntime(1404): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1033) 06-18 23:18:30.547: ERROR/AndroidRuntime(1404): at android.os.Handler.dispatchMessage(Handler.java:99) 06-18 23:18:30.547: ERROR/AndroidRuntime(1404): at android.os.Looper.loop(Looper.java:143) 06-18 23:18:30.547: ERROR/AndroidRuntime(1404): at android.app.ActivityThread.main(ActivityThread.java:4196) 06-18 23:18:30.547: ERROR/AndroidRuntime(1404): at java.lang.reflect.Method.invokeNative(Native Method) 06-18 23:18:30.547: ERROR/AndroidRuntime(1404): at java.lang.reflect.Method.invoke(Method.java:507) 06-18 23:18:30.547: ERROR/AndroidRuntime(1404): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839) 06-18 23:18:30.547: ERROR/AndroidRuntime(1404): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597) 06-18 23:18:30.547: ERROR/AndroidRuntime(1404): at dalvik.system.NativeStart.main(Native Method) 06-18 23:18:30.547: ERROR/AndroidRuntime(1404): Caused by: java.lang.NullPointerException 06-18 23:18:30.547: ERROR/AndroidRuntime(1404): at android.widget.TabHost$ViewIdContentStrategy.<init>(TabHost.java:591) 06-18 23:18:30.547: ERROR/AndroidRuntime(1404): at android.widget.TabHost$ViewIdContentStrategy.<init>(TabHost.java:586) 06-18 23:18:30.547: ERROR/AndroidRuntime(1404): at android.widget.TabHost$TabSpec.setContent(TabHost.java:441) 06-18 23:18:30.547: ERROR/AndroidRuntime(1404): at com.moonlight.tabbarexample.TabBarExample.onCreate(TabBarExample.java:26) 06-18 23:18:30.547: ERROR/AndroidRuntime(1404): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1093) 06-18 23:18:30.547: ERROR/AndroidRuntime(1404): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1780) 06-18 23:18:30.547: ERROR/AndroidRuntime(1404): ... 11 more 06-18 23:20:06.984: ERROR/SettingsAppWidhetProvider(14282): level1 = 100.0

谢谢设拉子

Thanks Shiraz

编辑2 - 这里的main.xml

EDIT 2 -- HERE IS main.xml

<?xml version="1.0" encoding="utf-8"?> <TabHost xmlns:android="schemas.android/apk/res/android" android:id="@android:id/tabhost" android:layout_width="fill_parent" android:layout_height="fill_parent"> <LinearLayout android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" android:padding="5dip"> <TabWidget android:id="@android:id/tabs" android:layout_width="fill_parent" android:layout_height="wrap_content" /> <FrameLayout android:id="@android:id/tabcontent" android:layout_width="fill_parent" android:layout_height="fill_parent" android:padding="5dip" /> </LinearLayout> </TabHost>

下面是TabbarExample清单

Here is TabbarExample manifest

<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="schemas.android/apk/res/android" package="com.moonlight.tabbarexample" android:versionCode="1" android:versionName="1.0"> <uses-sdk android:minSdkVersion="7" /> <application android:icon="@drawable/icon" android:label="@string/app_name"> <activity android:name=".TabBarExample" android:label="@string/app_name"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application> </manifest>

这是Firsttab.java

And here is Firsttab.java

package com.moonlight.tabbarexample; import android.app.Activity; import android.os.Bundle; import android.widget.TextView; public class FirstTab extends Activity{ public void onCreate ( Bundle savedInstanceState){ super.onCreate(savedInstanceState); /* First Tab Content */ TextView textView = new TextView(this); textView.setText("First Tab"); setContentView(textView); } }

最后一个SeconTab.java

last one SeconTab.java

package com.moonlight.tabbarexample; import android.app.Activity; import android.os.Bundle; import android.widget.TextView; public class SecondTab extends Activity{ public void onCreate ( Bundle savedInstanceState){ super.onCreate(savedInstanceState); /* First Tab Content */ TextView textView = new TextView(this); textView.setText("Second Tab"); setContentView(textView); } }

谢谢你们，pleaes healp，我焦急地等待着。问候。设拉子

Thanks guys, pleaes healp, i am anxiously waiting. Regards. Shiraz

编辑3 ---

我已经添加了这些下面一行到我的清单文件

I have added these following line to my manifest file

<activity android:name=".FirstTab"/> <activity android:name=".SecondTab"/>

但我仍然得到同样的错误：（

but I am still getting the same error :(

这是我的主要活动线路的onCreate methid我在哪里得到这个错误

this is the line in my main activity onCreate methid where i am getting this error

/** * add the created tab to the tab host for display **/ tabHost.addTab(spec1); tabHost.addTab(spec2);

谢谢设拉子

thanks shiraz

推荐答案

首先，定义为您的清单中的两个选项卡活动：

First, define the activities for the two tabs in your manifest:

<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="schemas.android/apk/res/android" package="com.moonlight.tabbarexample" android:versionCode="1" android:versionName="1.0"> <uses-sdk android:minSdkVersion="7" /> <application android:icon="@drawable/icon" android:label="@string/app_name"> <activity android:name=".FirstTab" /> <activity android:name=".SecondTab" /> <activity android:name=".TabBarExample" android:label="@string/app_name"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application> </manifest>

最后，改变

public class TabBarExample extends Activity {

到

public class TabBarExample extends TabActivity {

您的标签活动类的声明就好了。

The class declarations for your tab activities are just fine.