3

我正在开发应用程序，其中第一个活动从数据库中获取随机值并将其作为字符串发送到下一个活动。

我确切地知道如何在 sql 中做到这一点：

SELECT column FROM table
ORDER BY RANDOM()
LIMIT 1

经过一些尝试在应用程序中使用它后，我得出了这个结论：

Cursor send = database.query(TABLE_NAME, new String[] { COLUMN_NAME }, null, null, null, null, "RANDOM() LIMIT 1");

Bundle b = new Bundle();
b.putString("description", send.getString(send.getColumnIndex(COLUMN_NAME)));

但是在按下按钮打开第二个活动后，我在最后一行出现错误。

添加日志：

05-22 22:14:24.202: E/AndroidRuntime(14259): FATAL EXCEPTION: main
05-22 22:14:24.202: E/AndroidRuntime(14259): android.database.CursorIndexOutOfBoundsException: Index 1 requested, with a size of 1
05-22 22:14:24.202: E/AndroidRuntime(14259):    at android.database.AbstractCursor.checkPosition(AbstractCursor.java:400)
05-22 22:14:24.202: E/AndroidRuntime(14259):    at android.database.AbstractWindowedCursor.checkPosition(AbstractWindowedCursor.java:136)
05-22 22:14:24.202: E/AndroidRuntime(14259):    at android.database.AbstractWindowedCursor.getString(AbstractWindowedCursor.java:50)
05-22 22:14:24.202: E/AndroidRuntime(14259): at com.example.ListAction$1.onItemClick(ListAction.java:90)
05-22 22:14:24.202: E/AndroidRuntime(14259):    at android.widget.AdapterView.performItemClick(AdapterView.java:292)
05-22 22:14:24.202: E/AndroidRuntime(14259):    at android.widget.AbsListView.performItemClick(AbsListView.java:1177)
05-22 22:14:24.202: E/AndroidRuntime(14259):    at android.widget.AbsListView$PerformClick.run(AbsListView.java:2705)
05-22 22:14:24.202: E/AndroidRuntime(14259):    at android.widget.AbsListView$1.run(AbsListView.java:3458)
05-22 22:14:24.202: E/AndroidRuntime(14259):    at android.os.Handler.handleCallback(Handler.java:605)
05-22 22:14:24.202: E/AndroidRuntime(14259):    at android.os.Handler.dispatchMessage(Handler.java:92)
05-22 22:14:24.202: E/AndroidRuntime(14259):    at android.os.Looper.loop(Looper.java:137)
05-22 22:14:24.202: E/AndroidRuntime(14259):    at android.app.ActivityThread.main(ActivityThread.java:4507)
05-22 22:14:24.202: E/AndroidRuntime(14259):    at java.lang.reflect.Method.invokeNative(Native Method)
05-22 22:14:24.202: E/AndroidRuntime(14259):    at java.lang.reflect.Method.invoke(Method.java:511)
05-22 22:14:24.202: E/AndroidRuntime(14259):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:790)
05-22 22:14:24.202: E/AndroidRuntime(14259):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:557)
05-22 22:14:24.202: E/AndroidRuntime(14259):    at dalvik.system.NativeStart.main(Native Method)
4

2 回答 2

2

我认为问题在于您应该将光标指向第一行。我没有在你的代码中找到这个：

if (!send.moveToFirst()) {
    Log.d(TAG, "Cannot move to first row of the Cursor!");
    return;
}
于 2012-05-22T20:57:28.823 回答
1

改用rawQuery：

database.rawQuery("SELECT column 
                   FROM table 
                   ORDER BY RANDOM() LIMIT 1",null);

您将获得与cursor通常在 sql 中执行的相同类型但执行查询的查询。

因此，假设您的代码的第二部分是正确的：

Cursor send =database.rawQuery("SELECT column 
                   FROM table 
                   ORDER BY RANDOM() LIMIT 1",null);
Bundle b = new Bundle();
b.putString("description", send.getString(send.getColumnIndex(COLUMN_NAME)));
于 2012-05-22T18:16:31.483 回答