我的
Android应用中的数据访问
代码引发了异常.
以下是导致异常的代码：
@H_
502_4@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);
....
}
提出的例外是：
@H_
502_4@android.database.CursorIndexOutOfBoundsException: Index 2 requested,with a size of 2 exception
log方法生成结果2个后行.
这有什么不对？
编辑：
我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.
@H_
502_4@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
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：
@H_
502_4@if (result != null && result.moveToFirst()){
do {
Post post = new Post();
post.setPostId(result.getInt(0));
posts.add(post);
....
} while (result.moveToNext());
}
现在它应该正常工作.
注意：不要忘记调用moveToFirst()方法将Cursor移动到第一个记录(隐式位于第一行之前)并准备读取.这也是测试Cursor是否有效的方便方法.
注意2：不要使用列索引,你可以简单地计算错误.而不是使用列名 – 通常建议使用此方法. cursor.getColumnIndex( “< COLUMNNAME>” 中)
