如果 TabHost 访问 ListActivity -> Nullpointer 异常答案

【问题标题】：If TabHost acces ListActivity -> Nullpointer Exception如果 TabHost 访问 ListActivity -> Nullpointer 异常
【发布时间】：2011-09-13 11:09:42
【问题描述】：

我创建了一个带有不可见 TabHost 的 Activity，它从我的数据库填充的 ListActivity 中获取内容。如果我用 TabHost 打开我的 Activity，我会收到强制关闭错误。问题可能出在我的 ListActivity 中。

这是我在 Tabhost 中的活动代码：

package de.retowaelchli.filterit;


import de.retowaelchli.filterit.stats.CreatedADFilters;
import android.app.TabActivity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.TabHost;


public class ADeleteActivity extends TabActivity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.autodelete_test);

        TabHost tabHost = getTabHost();       

        tabHost.addTab(tabHost.newTabSpec("tab1").setIndicator("All AutodeleteFilters").setContent(new Intent(this, CreatedADFilters.class)));
        tabHost.setCurrentTab(0);


    }
    /** Verweise auf die anderen Seiten **/
    public void onClickADConfig(View view){
        final Intent i = new Intent(this, ADFilterConfigActivity.class);
        startActivity(i); }
}

这是它的布局文件：

<?xml version="1.0" encoding="utf-8"?>


<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@android:id/tabcontent"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

       <TabHost xmlns:android="http://schemas.android.com/apk/res/android"
        android:id="@android:id/tabhost"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent">

        <RelativeLayout
           android:orientation="vertical"
           android:layout_width="fill_parent"
           android:layout_height="fill_parent">
           <FrameLayout
               android:id="@android:id/tabcontent"
               android:layout_width="fill_parent"
               android:layout_height="fill_parent"
               android:layout_weight="1" />
               <TabWidget
                   android:id="@android:id/tabs"
                   android:layout_width="fill_parent"
                   android:layout_height="wrap_content"
                   android:layout_alignBottom = "@android:id/tabcontent" 
                   android:visibility="invisible"/>

                   <TableRow 
                       android:layout_height="wrap_content" 
                       android:id="@+id/ADFilterOverview" 
                       android:layout_width="match_parent" 
                       android:onClick="onClickADConfig" 
                       android:layout_alignParentBottom="true" 
                       android:layout_alignParentLeft="true">

                        <TextView 
                        android:layout_gravity="bottom|left" 
                        android:text="@string/newadfilter" 
                        style="@style/NormalFont"/>
                </TableRow>
       </RelativeLayout>
      </TabHost>  
  </FrameLayout>

现在您可以在这里看到我的 ListActivity 的代码：

package de.retowaelchli.filterit.stats;


import de.retowaelchli.filterit.R;
import de.retowaelchli.filterit.database.ADFilterDBAdapter;
import android.app.ListActivity;
import android.database.Cursor;
import android.os.Bundle;
import android.widget.SimpleCursorAdapter;


public class CreatedADFilters extends ListActivity {

    //Variablen deklaration
    private ADFilterDBAdapter mDbHelper;

    public void onCreate(Bundle icicle) {
        super.onCreate(icicle);

        mDbHelper=new ADFilterDBAdapter(this);
        fillData();

    }
    private void fillData() {
        // Get all of the notes from the database and create the item list
        Cursor c = mDbHelper.getAllADFilter();
        startManagingCursor(c);

        String[] from = new String[] { mDbHelper.NAME };
        int[] to = new int[] { R.id.empty };

        // Now create an array adapter and set it to display using our row
        SimpleCursorAdapter adname =
            new SimpleCursorAdapter(this, R.layout.list_layout, c, from, to);
        setListAdapter(adname);
    }
}

这是它的布局文件：

<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
    style="@style/NormalFont"
    android:id="@+id/empty" >
</TextView>

那么我做错了什么.. :(

提前谢谢你。

最好的问候

野生动物园

这是 LogCat。

09-13 14:20:11.652: INFO/ActivityManager(1721): Starting activity: Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10100000 cmp=de.retowaelchli.filterit/.StartseiteActivity } from pid 1721
09-13 14:20:11.672: VERBOSE/HtcAppUsageStats(1721): (launch app, package): (Filter It, de.retowaelchli.filterit)
09-13 14:20:11.672: DEBUG/StatusBarManagerService(1721): disable what =0, token = android.os.Binder@40841360, pkg = android, mBar = com.android.internal.statusbar.IStatusBar$Stub$Proxy@40b46bb8
09-13 14:20:11.672: INFO/ActivityManager(1721): Start proc de.retowaelchli.filterit for activity de.retowaelchli.filterit/.StartseiteActivity: pid=3992 uid=10150 gids={}
09-13 14:20:11.812: INFO/SuperPowerSvc(29815): [SuperPowerSvc] App launched: [de.retowaelchli.filterit]
09-13 14:20:12.002: DEBUG/dalvikvm(1721): GC_EXTERNAL_ALLOC freed 1394K, 34% free 10500K/15815K, external 10208K/12256K, paused 147ms
09-13 14:20:12.232: WARN/ResourceType(1721): Skipping entry 0x7f040007 in package table 0 because it is not complex!
09-13 14:20:12.232: WARN/ResourceType(1721): Skipping entry 0x7f040008 in package table 0 because it is not complex!
09-13 14:20:12.272: DEBUG/SurfaceFlinger(1721): layer=0xc46a48 is not in the purgatory list
09-13 14:20:12.292: DEBUG/dalvikvm(3992): GC_EXTERNAL_ALLOC freed 44K, 50% free 2695K/5379K, external 0K/0K, paused 25ms
09-13 14:20:12.442: WARN/InputManagerService(1721): [unbindCurrentClientLocked] Disable input method client.
09-13 14:20:12.442: WARN/InputManagerService(1721): [startInputLocked] Enable input method client.
09-13 14:20:12.512: INFO/ActivityManager(1721): Displayed de.retowaelchli.filterit/.StartseiteActivity: +837ms
09-13 14:20:13.472: INFO/ActivityManager(1721): Starting activity: Intent { cmp=de.retowaelchli.filterit/.ADeleteActivity } from pid 3992
09-13 14:20:13.502: INFO/SuperPowerSvc(29815): [SuperPowerSvc] App launched: [de.retowaelchli.filterit]
09-13 14:20:13.622: DEBUG/dalvikvm(3992): GC_EXTERNAL_ALLOC freed 36K, 49% free 2769K/5379K, external 5760K/7192K, paused 22ms
09-13 14:20:13.742: DEBUG/AndroidRuntime(3992): Shutting down VM
09-13 14:20:13.742: WARN/dalvikvm(3992): threadid=1: thread exiting with uncaught exception (group=0x4001d5a0)
09-13 14:20:13.742: ERROR/AndroidRuntime(3992): FATAL EXCEPTION: main
09-13 14:20:13.742: ERROR/AndroidRuntime(3992): java.lang.RuntimeException: Unable to start activity ComponentInfo{de.retowaelchli.filterit/de.retowaelchli.filterit.ADeleteActivity}: java.lang.RuntimeException: Unable to start activity ComponentInfo{de.retowaelchli.filterit/de.retowaelchli.filterit.stats.CreatedADFilters}: java.lang.NullPointerException
09-13 14:20:13.742: ERROR/AndroidRuntime(3992):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1816)
09-13 14:20:13.742: ERROR/AndroidRuntime(3992):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1837)
09-13 14:20:13.742: ERROR/AndroidRuntime(3992):     at android.app.ActivityThread.access$1500(ActivityThread.java:132)
09-13 14:20:13.742: ERROR/AndroidRuntime(3992):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1033)
09-13 14:20:13.742: ERROR/AndroidRuntime(3992):     at android.os.Handler.dispatchMessage(Handler.java:99)
09-13 14:20:13.742: ERROR/AndroidRuntime(3992):     at android.os.Looper.loop(Looper.java:143)
09-13 14:20:13.742: ERROR/AndroidRuntime(3992):     at android.app.ActivityThread.main(ActivityThread.java:4196)
09-13 14:20:13.742: ERROR/AndroidRuntime(3992):     at java.lang.reflect.Method.invokeNative(Native Method)
09-13 14:20:13.742: ERROR/AndroidRuntime(3992):     at java.lang.reflect.Method.invoke(Method.java:507)
09-13 14:20:13.742: ERROR/AndroidRuntime(3992):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
09-13 14:20:13.742: ERROR/AndroidRuntime(3992):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
09-13 14:20:13.742: ERROR/AndroidRuntime(3992):     at dalvik.system.NativeStart.main(Native Method)
09-13 14:20:13.742: ERROR/AndroidRuntime(3992): Caused by: java.lang.RuntimeException: Unable to start activity ComponentInfo{de.retowaelchli.filterit/de.retowaelchli.filterit.stats.CreatedADFilters}: java.lang.NullPointerException
09-13 14:20:13.742: ERROR/AndroidRuntime(3992):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1816)
09-13 14:20:13.742: ERROR/AndroidRuntime(3992):     at android.app.ActivityThread.startActivityNow(ActivityThread.java:1651)
09-13 14:20:13.742: ERROR/AndroidRuntime(3992):     at android.app.LocalActivityManager.moveToState(LocalActivityManager.java:127)
09-13 14:20:13.742: ERROR/AndroidRuntime(3992):     at android.app.LocalActivityManager.startActivity(LocalActivityManager.java:339)
09-13 14:20:13.742: ERROR/AndroidRuntime(3992):     at android.widget.TabHost$IntentContentStrategy.getContentView(TabHost.java:656)
09-13 14:20:13.742: ERROR/AndroidRuntime(3992):     at android.widget.TabHost.setCurrentTab(TabHost.java:326)
09-13 14:20:13.742: ERROR/AndroidRuntime(3992):     at android.widget.TabHost.addTab(TabHost.java:216)
09-13 14:20:13.742: ERROR/AndroidRuntime(3992):     at de.retowaelchli.filterit.ADeleteActivity.onCreate(ADeleteActivity.java:22)
09-13 14:20:13.742: ERROR/AndroidRuntime(3992):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1093)
09-13 14:20:13.742: ERROR/AndroidRuntime(3992):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1780)
09-13 14:20:13.742: ERROR/AndroidRuntime(3992):     ... 11 more
09-13 14:20:13.742: ERROR/AndroidRuntime(3992): Caused by: java.lang.NullPointerException
09-13 14:20:13.742: ERROR/AndroidRuntime(3992):     at de.retowaelchli.filterit.database.ADFilterDBAdapter.getAllADFilter(ADFilterDBAdapter.java:108)
09-13 14:20:13.742: ERROR/AndroidRuntime(3992):     at de.retowaelchli.filterit.stats.CreatedADFilters.fillData(CreatedADFilters.java:26)
09-13 14:20:13.742: ERROR/AndroidRuntime(3992):     at de.retowaelchli.filterit.stats.CreatedADFilters.onCreate(CreatedADFilters.java:21)
09-13 14:20:13.742: ERROR/AndroidRuntime(3992):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1093)
09-13 14:20:13.742: ERROR/AndroidRuntime(3992):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1780)
09-13 14:20:13.742: ERROR/AndroidRuntime(3992):     ... 20 more
09-13 14:20:13.752: WARN/ActivityManager(1721):   Force finishing activity de.retowaelchli.filterit/.ADeleteActivity
09-13 14:20:13.752: WARN/ActivityManager(1721):   Force finishing activity de.retowaelchli.filterit/.StartseiteActivity
09-13 14:20:14.262: WARN/ActivityManager(1721): Activity pause timeout for HistoryRecord{4058e8d8 de.retowaelchli.filterit/.ADeleteActivity}
09-13 14:20:14.352: WARN/ResourceType(1721): Skipping entry 0x7f040006 in package table 0 because it is not complex!
09-13 14:20:14.352: WARN/ResourceType(1721): Skipping entry 0x7f040005 in package table 0 because it is not complex!

帖子已更新为新的 Logcat 和过度代码，来自您的帖子！

【问题讨论】：

标签： android nullpointerexception android-tabhost

【解决方案1】：

您没有为 ADFilterDBAdapter 创建对象

 public void onCreate(Bundle icicle) {
    super.onCreate(icicle);

    mDbHelper=new ADFilterDBAdapter(this);
    fillData();

}

此外，根据您的代码，您只创建了一个选项卡。所以将当前选项卡索引设置为零（索引从零开始）

tabHost.setCurrentTab(0);

【讨论】：

嘿巴拉吉，我做了你说的两个改变，但我仍然得到 ForceClose 错误！ :(

【解决方案2】：

设置 tabHost.setCurrentTab(0);而不是 tabHost.setCurrentTab(1);

这就是“NullPointerException”的原因。

【讨论】：

【解决方案3】：

我发现了，这是一个数据库问题，表不存在。谢谢你的帮助：D

【讨论】：