java - android.database.CursorIndexOutOfBoundsException异常

Question

我的 Android 应用程序中的数据访问代码引发异常。

这是导致异常的代码:

String getPost = "SELECT * FROM " + TABLE_POST + ";";
Cursor result = getReadableDatabase().rawQuery(getPost, null);
List posts = new ArrayList();{
Log.d("count", result.getCount() + " post rows");
while (result != null && result.moveToNext());
    Post post = new Post();
    post.setPostId(result.getInt(0));
    posts.add(post);
    ....
}

引发的异常是:

android.database.CursorIndexOutOfBoundsException: Index 2 requested, with a size of 2 exception

log 方法产生结果 2 post rows。

这里有什么问题吗？

编辑:我已经添加了完整的堆栈跟踪，以便那些希望查看它的人可以这样做。

11-14 09:57:50.538: W/dalvikvm(4710): threadid=1: thread exiting with uncaught exception (group=0x40a71930)
11-14 09:57:50.608: E/AndroidRuntime(4710): FATAL EXCEPTION: main
11-14 09:57:50.608: E/AndroidRuntime(4710): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.innolabmm.software.collaboration/com.innolabmm.software.collaboration.PostCommentActivity}: android.database.CursorIndexOutOfBoundsException: Index 2 requested, with a size of 2
11-14 09:57:50.608: E/AndroidRuntime(4710):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
11-14 09:57:50.608: E/AndroidRuntime(4710):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
11-14 09:57:50.608: E/AndroidRuntime(4710):     at android.app.ActivityThread.access$600(ActivityThread.java:141)
11-14 09:57:50.608: E/AndroidRuntime(4710):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
11-14 09:57:50.608: E/AndroidRuntime(4710):     at android.os.Handler.dispatchMessage(Handler.java:99)
11-14 09:57:50.608: E/AndroidRuntime(4710):     at android.os.Looper.loop(Looper.java:137)
11-14 09:57:50.608: E/AndroidRuntime(4710):     at android.app.ActivityThread.main(ActivityThread.java:5041)
11-14 09:57:50.608: E/AndroidRuntime(4710):     at java.lang.reflect.Method.invokeNative(Native Method)
11-14 09:57:50.608: E/AndroidRuntime(4710):     at java.lang.reflect.Method.invoke(Method.java:511)
11-14 09:57:50.608: E/AndroidRuntime(4710):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
11-14 09:57:50.608: E/AndroidRuntime(4710):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
11-14 09:57:50.608: E/AndroidRuntime(4710):     at dalvik.system.NativeStart.main(Native Method)
11-14 09:57:50.608: E/AndroidRuntime(4710): Caused by: android.database.CursorIndexOutOfBoundsException: Index 2 requested, with a size of 2
11-14 09:57:50.608: E/AndroidRuntime(4710):     at android.database.AbstractCursor.checkPosition(AbstractCursor.java:424)
11-14 09:57:50.608: E/AndroidRuntime(4710):     at android.database.AbstractWindowedCursor.checkPosition(AbstractWindowedCursor.java:136)
11-14 09:57:50.608: E/AndroidRuntime(4710):     at android.database.AbstractWindowedCursor.getInt(AbstractWindowedCursor.java:68)
11-14 09:57:50.608: E/AndroidRuntime(4710):     at com.innolabmm.software.collaboration.data.CollaborationDbHandler.fetchAllPost(CollaborationDbHandler.java:362)
11-14 09:57:50.608: E/AndroidRuntime(4710):     at com.innolabmm.software.collaboration.PostCommentActivity.onCreate(PostCommentActivity.java:48)
11-14 09:57:50.608: E/AndroidRuntime(4710):     at android.app.Activity.performCreate(Activity.java:5104)
11-14 09:57:50.608: E/AndroidRuntime(4710):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
11-14 09:57:50.608: E/AndroidRuntime(4710):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
11-14 09:57:50.608: E/AndroidRuntime(4710):     ... 11 more

Answer 1

您正在尝试检索索引 2 上的项目，但该索引确实不存在(游标大小为 2，因此索引为 0,1)。

改变你的循环:

if (result != null && result.moveToFirst()){
    do {
       Post post = new Post();
       post.setPostId(result.getInt(0));
       posts.add(post);
       ....
    } while (result.moveToNext());
}

现在它应该可以正常工作了。

注意:别忘了调用moveToFirst()将 Cursor 移动到第一条记录(隐式位于第一行之前)并准备读取它的方法。这也是测试 Cursor 是否有效的便捷方法。

注意2:不要使用列索引，你很容易在计数时出错。而不是使用列名 - 通常推荐这种方法 e.q. cursor.getColumnIndex("<columnName>")