Question

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。

我确切知道如何在sql中完成：

SELECT column FROM table
ORDER BY RANDOM()
LIMIT 1

在尝试在应用程序中使用它之后，我来到了这个：

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)));

但按下按钮打开第二个活动后，我在最后一行收到错误。

添加了日志：

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)

Answer 1

我认为问题是您应该将光标指向第一行。我在你的代码中找不到这个：

if (!send.moveToFirst()) {
    Log.d(TAG, "Cannot move to first row of the Cursor!");
    return;
}

Answer 2

改为使用rawQuery：

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

您将获得相同类型的cursor，但正如您在sql中通常所做的那样执行查询。

所以假设你的第二部分代码是正确的：

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)));

如何从数据库中获取随机字符串？

2 个答案: