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游标找不到列?

sqlite android

1

xZise · 技术社区 · 15 年前

有缺陷的代码:

public final AccessToken[] fetchAccessTokenByServerId(final long serverId) {
    final Cursor c = db.query(
            ACCESS_TOKEN_TABLE,
            new String[] { ACCESS_TOKEN_COL_ID, ACCESS_TOKEN_COL_VALUE },
            ACCESS_TOKEN_COL_SERVER_ID + "=?",
            new String[] { Long.toString(serverId) },
            null,
            null,
            null);

    AccessToken[] result = new AccessToken[c.getCount()];
    for (int i = 0; i < result.length; i++) {
        long id = c.getLong(c.getColumnIndexOrThrow(ACCESS_TOKEN_COL_ID));
        String value = c.getString(c.getColumnIndexOrThrow(ACCESS_TOKEN_COL_VALUE));

        result[i] = new AccessToken(value, id, serverId);
        c.moveToNext();
    }
    return result;
}

public static final String COL_ID = "_id";
public static final String ACCESS_TOKEN_TABLE = "accesstoken";
public static final String ACCESS_TOKEN_COL_ID = COL_ID;
public static final String ACCESS_TOKEN_COL_SERVER_ID = "server_id";
public static final String ACCESS_TOKEN_COL_VALUE = "value";

但是for循环中的前两个语句失败:

请求索引-1,大小为

表存在列:yId(=int)、ServyId(= int)和值(=字符串)

有一个条目:1,1,test

真诚的西泽

2 回复 | 直到 15 年前

1

3

Cristian 15 年前

初始化光标后,请执行以下操作:

c.moveToFirst();

2

t0mm13b 15 年前

原件:

AccessToken[] result = new AccessToken[c.getCount()];
for (int i = 0; i < result.length; i++) {
    long id = c.getLong(c.getColumnIndexOrThrow(ACCESS_TOKEN_COL_ID));
    String value = c.getString(c.getColumnIndexOrThrow(ACCESS_TOKEN_COL_VALUE));

    result[i] = new AccessToken(value, id, serverId);
    c.moveToNext();
}

被改进的:

if (c.moveToFirst()){
   int rowCount = c.getCount();
   AccessToken[] result = new AccessToken(rowCount);
   int recCount = 0;
   while (!c.isAfterLast()){
        long id = c.getLong(c.getColumnIndexOrThrow(ACCESS_TOKEN_COL_ID));
        String value = c.getString(c.getColumnIndexOrThrow(ACCESS_TOKEN_COL_VALUE));

        result[recCount++] = new AccessToken(value, id, serverId);
        c.moveToNext();
   }
   c.close(); // <-- IMPORTANT!!!!
}