Android 和 SQLite - 从表中检索最大 id [英] Android and SQLite - retrieve max id from table

问题描述

我正在尝试创建方法来从我的表中检索最大 ID，但我遇到了问题.

I am trying to create method to retrieve the max id from my table but I've problem.

这是我的方法.它正在工作，但返回值为0，

This is my method. It's working, but return value is 0,

public int getLastId() {
    openDB();
    int id = 0;
    final String MY_QUERY = "SELECT MAX(_id) AS _id FROM organize";
    Cursor mCursor = mDb.rawQuery(MY_QUERY, null);  
    try {
          if (mCursor.getCount() > 0) {
            mCursor.moveToFirst();
            id = mCursor.getInt(mCursor.getColumnIndex(MY_QUERY));
          }
        } catch (Exception e) {
          System.out.println(e.getMessage());
        } finally {
            closeDB();
        }
return id;

}

我能解决这个问题吗，非常感谢

can I fix this problem, thanks a lot

推荐答案

重写这一行

id = mCursor.getInt(mCursor.getColumnIndex(MY_QUERY));

到

id = mCursor.getInt(mCursor.getColumnIndex("_id"));  

或者更好

id = mCursor.getInt(0);//there's only 1 column in cursor since you only get MAX, not dataset

看看 LogCat，它会告诉你你的问题.

And look at LogCat, it will tell you about your problem.

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