Android 带有ListView和setAdapter的NullPointerException

我一直收到以下nullPointerException，我不太明白，如果您能提供任何帮助，我将不胜感激。从DB中删除程序query（），然后使用适配器填充ListView

   public class ViewListingsActivity extends Activity {
    SQLiteDatabase db;
    ListView listview;
    Button button;
    SimpleCursorAdapter adapter;
    private static final String TAG = DBHelper.class.getSimpleName();
    public static final String DB_ADDRESS = BaseColumns._ID;
    public static final String DB_DESCRIPTION = "Description";
    public static final String DB_URL = "URL";
    final String dbTable = "Realtor_SMS_Table";

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.viewlisting);
        listview = (ListView) findViewById(R.id.list);
        button = (Button) findViewById(R.id.button1);
        DBHelper dbhelper = new DBHelper(ViewListingsActivity.this);
        db = dbhelper.getWritableDatabase();

        Cursor cursor = db.query(dbTable, null, null, null, null, null, null);
        startManagingCursor(cursor);

        String[] from = new String[] { DB_ADDRESS, DB_DESCRIPTION, DB_URL };
        int[] to = new int[] { R.id.textlistaddress, R.id.textlistdescription,
                R.id.textlisturl };
        adapter = new SimpleCursorAdapter(this, R.layout.rowlist, cursor, from,
                to);
        listview.setAdapter(adapter);

    }
}

这是我的堆栈跟踪

----- pid 764 at 2011-08-05 13:26:24 -----
Cmd line: com.RealtorSMS

DALVIK THREADS:
"main" prio=5 tid=3 NATIVE
  | group="main" sCount=1 dsCount=0 s=0 obj=0x40018e70
  | sysTid=764 nice=0 sched=0/0 handle=-1096475492
  at android.os.BinderProxy.transact(Native Method)
  at android.app.ActivityManagerProxy.handleApplicationError(ActivityManagerNative.java:2103)
  at com.android.internal.os.RuntimeInit.crash(RuntimeInit.java:302)
  at com.android.internal.os.RuntimeInit$UncaughtHandler.uncaughtException(RuntimeInit.java:75)
  at java.lang.ThreadGroup.uncaughtException(ThreadGroup.java:887)
  at java.lang.ThreadGroup.uncaughtException(ThreadGroup.java:884)
  at dalvik.system.NativeStart.main(Native Method)

"Binder Thread #3" prio=5 tid=15 NATIVE
  | group="main" sCount=1 dsCount=0 s=0 obj=0x43594008
  | sysTid=771 nice=0 sched=0/0 handle=1505008
  at dalvik.system.NativeStart.run(Native Method)

"Binder Thread #2" prio=5 tid=13 NATIVE
  | group="main" sCount=1 dsCount=0 s=0 obj=0x43590120
  | sysTid=770 nice=0 sched=0/0 handle=1487504
  at dalvik.system.NativeStart.run(Native Method)

"Binder Thread #1" prio=5 tid=11 NATIVE
  | group="main" sCount=1 dsCount=0 s=0 obj=0x4358e9b0
  | sysTid=769 nice=0 sched=0/0 handle=1396928
  at dalvik.system.NativeStart.run(Native Method)

"JDWP" daemon prio=5 tid=9 VMWAIT
  | group="system" sCount=1 dsCount=0 s=0 obj=0x4358d2a0
  | sysTid=768 nice=0 sched=0/0 handle=1493656
  at dalvik.system.NativeStart.run(Native Method)

"Signal Catcher" daemon prio=5 tid=7 RUNNABLE
  | group="system" sCount=0 dsCount=0 s=0 obj=0x4358d1e8
  | sysTid=767 nice=0 sched=0/0 handle=1490832
  at dalvik.system.NativeStart.run(Native Method)

"HeapWorker" daemon prio=5 tid=5 VMWAIT
  | group="system" sCount=1 dsCount=0 s=0 obj=0x427d1928
  | sysTid=765 nice=0 sched=0/0 handle=1488192
  at dalvik.system.NativeStart.run(Native Method)

----- end 764 -----

下面是两个XML

rowlist.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  android:orientation="vertical"
  android:layout_width="match_parent"
  android:layout_height="match_parent">
    <TextView android:layout_height="wrap_content" android:text="TextView" android:layout_width="match_parent" android:id="@+id/textlistaddress"></TextView>
    <TextView android:layout_height="wrap_content" android:text="TextView" android:layout_width="match_parent" android:id="@+id/textlistdescription"></TextView>
    <TextView android:layout_height="wrap_content" android:text="TextView" android:layout_width="match_parent" android:id="@+id/textlisturl"></TextView>

</LinearLayout>

---

检查viewlisting.xml，它不包含id为R.id.list的ListView

我想编译器或Eclipse可能有问题。 我今晚也遇到了这个问题。但是在我重命名了

列表视图ID

，并且重新编译了XML文件之后，它就可以工作了

---

我发现有时候，XML文件中的更改不会自动重建。有时，XML文件的生成结果似乎丢失了。

在Eclipse Project->Clean中运行检查您是否有这一行的add-in onCreate类方法：

setContentView（R.layout.your_xml）

我也有同样的问题。 我发现我使用了带有错误参数的

setcontentview（）

，因为我从另一个类复制并粘贴了代码。

---

我纠正了错误的论点，问题解决了

Proapp Aplicativos的回答是：“检查您是否在创建类方法这一行中有外接程序： setContentView（R.layout.your_xml）；”

---

帮助我解决了一个问题。

请粘贴堆栈跟踪。根据设置，似乎有一些内容可能为空。哪一行抛出nullPointerException，是的，我们可以得到堆栈跟踪吗？根据调试，它使用最后一行listview.setAdapter（adapter）；抱歉，我的意思是viewlisting.xml:），因为如果在listview.setAdapter（适配器）中有NullPointerException；行表示listview为空，并且listview=（listview）findViewById（R.id.list）未找到它；viewlisting.xml文件在ListView标记中确实具有正确的id，或者我缺少什么？XML已经粘贴到了instrange中，看起来还可以，你能从ddms粘贴stacktrace吗？好的，所以在疯狂了大约20分钟后，我决定从Activity更改为ListActivity，但这不起作用，所以我将其更改为重新编译关机、eclipse和avd，然后重新启动，突然它起了作用。你难道不喜欢日食的浮躁吗。不知道为什么我总是在其他Java工作中使用NetBeans。谢谢！这也是我的问题。我真傻。。再次感谢！

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent" android:background="@drawable/realtorbackground"
    android:weightSum="1">
    <TextView android:layout_weight="0.08" android:layout_height="wrap_content"
        android:layout_width="match_parent" android:id="@+id/textViewtitleview"
        android:gravity="center" android:textSize="30dp" android:text="Current Listings"></TextView>
    <ListView android:layout_width="fill_parent" android:layout_height="fill_parent" android:id="@+id/list"></ListView>
    <Button android:id="@+id/button1" android:layout_width="match_parent"
        android:layout_height="wrap_content" android:text="Delete Listing"></Button>

</LinearLayout>

08-05 13:26:24.077: ERROR/AndroidRuntime(764): Uncaught handler: thread main exiting due to uncaught exception
08-05 13:26:24.087: ERROR/AndroidRuntime(764): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.RealtorSMS/com.RealtorSMS.ViewListingsActivity}: java.lang.NullPointerException
08-05 13:26:24.087: ERROR/AndroidRuntime(764):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2268)
08-05 13:26:24.087: ERROR/AndroidRuntime(764):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2284)
08-05 13:26:24.087: ERROR/AndroidRuntime(764):     at android.app.ActivityThread.access$1800(ActivityThread.java:112)
08-05 13:26:24.087: ERROR/AndroidRuntime(764):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1692)
08-05 13:26:24.087: ERROR/AndroidRuntime(764):     at android.os.Handler.dispatchMessage(Handler.java:99)
08-05 13:26:24.087: ERROR/AndroidRuntime(764):     at android.os.Looper.loop(Looper.java:123)
08-05 13:26:24.087: ERROR/AndroidRuntime(764):     at android.app.ActivityThread.main(ActivityThread.java:3948)
08-05 13:26:24.087: ERROR/AndroidRuntime(764):     at java.lang.reflect.Method.invokeNative(Native Method)
08-05 13:26:24.087: ERROR/AndroidRuntime(764):     at java.lang.reflect.Method.invoke(Method.java:521)
08-05 13:26:24.087: ERROR/AndroidRuntime(764):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:782)
08-05 13:26:24.087: ERROR/AndroidRuntime(764):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:540)
08-05 13:26:24.087: ERROR/AndroidRuntime(764):     at dalvik.system.NativeStart.main(Native Method)
08-05 13:26:24.087: ERROR/AndroidRuntime(764): Caused by: java.lang.NullPointerException
08-05 13:26:24.087: ERROR/AndroidRuntime(764):     at com.RealtorSMS.ViewListingsActivity.onCreate(ViewListingsActivity.java:39)
08-05 13:26:24.087: ERROR/AndroidRuntime(764):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1123)
08-05 13:26:24.087: ERROR/AndroidRuntime(764):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2231)
08-05 13:26:24.087: ERROR/AndroidRuntime(764):     ... 11 more