Question

我正在写你，因为我试图找出如何让这个查询在Android上运行，我知道sintaxis没问题，因为我之前尝试过SQLite浏览器，但我不知道为什么它没有'在Android上给我任何结果，这是我在Android上使用的代码：

    public long getAdminOrMemberOrGroupID (String arg, char option){
    Cursor result = null;
    String[] selectionArgs = new String[] { arg };
    long idResult = 0;
    int idIndex=0;

    switch(option){
    case 'a':
        result = db.rawQuery("SELECT _id FROM Admins WHERE mac=?", selectionArgs);
        //result = db.rawQuery("SELECT _id FROM Admins WHERE mac= '"+ arg +"'", null);
        //result = db.query(DATABASE_TABLE_ADMINS, new String[]{KEY_ID}, KEY_MAC + "= '" + arg + "'" , null, null, null, null); 
    case 'm':
        result = db.rawQuery("SELECT _id FROM Members WHERE mac=?", selectionArgs);
        //result = db.rawQuery("SELECT _id FROM Members WHERE mac= '"+ arg +"'", null);
        //result = db.query(DATABASE_TABLE_MEMBERS, new String[]{KEY_ID}, KEY_MAC + "= '" + arg + "'", null, null, null, null);
    case 'g':
        result = db.rawQuery("SELECT _id FROM Groups WHERE name=?", selectionArgs);
        ////result = db.rawQuery("SELECT _id FROM Groups WHERE name= '"+ arg +"'", null);
        //result = db.query(DATABASE_TABLE_GROUPS, new String[]{KEY_ID}, KEY_NAME + "= '" + arg + "'", null, null, null, null);

    }

    idIndex = result.getColumnIndex(KEY_ID);

    if(result!=null){
        if (result.isFirst()){
             idResult= result.getLong(idIndex);
        }
    }

    return idResult;
}

正如你所看到的，我曾尝试过几种方式，但没有一种方法可以正常工作，它不会返回任何结果。我已经使用DDMS将数据库文件拖到我的电脑上，并在SQLite浏览器上尝试相同的查询，这是有效的。那么，之前显示的代码问题在哪里？

感谢您对此问题的任何帮助，

蒂姆，这是：

public static final String KEY_ID = "_id";
public static final String KEY_NAME = "name";
public static final int NAME_COLUMN = 1;
public static final String KEY_MAC = "mac";
public static final int MAC_COLUMN = 2;
public static final String KEY_GPS = "gps";
public static final int GPS_COLUMN = 3;
public static final String KEY_ID_ADMIN = "idAdmin";
public static final String KEY_ID_GROUP = "idGroup";

private static final String DATABASE_CREATE_ADMINS = "create table " + DATABASE_TABLE_ADMINS + 
"(" + KEY_ID + " integer primary key autoincrement, " + KEY_NAME + " text not null, " + KEY_MAC + " text not null);";
private static final String DATABASE_CREATE_GROUPS = "create table " + DATABASE_TABLE_GROUPS + 
"(" + KEY_ID + " integer primary key autoincrement, " + KEY_ID_ADMIN + " integer, " + KEY_NAME + " text not null);";
private static final String DATABASE_CREATE_MEMBERS = "create table " + DATABASE_TABLE_MEMBERS + 
"(" + KEY_ID + " integer primary key autoincrement, " + KEY_NAME + " text not null, " + KEY_MAC + " text not null, " 
    + KEY_GPS + " text, " + KEY_ID_GROUP + " integer);";

创建表的方法

public void createDataBase() throws IOException{

    boolean dbExist = checkDataBase();

    if(dbExist){
        //do nothing - database already exist
    }else{
        db = context.openOrCreateDatabase(DATABASE_NAME, SQLiteDatabase.CREATE_IF_NECESSARY, null);
        db.execSQL(DATABASE_CREATE_ADMINS);
        db.execSQL(DATABASE_CREATE_MEMBERS);
        db.execSQL(DATABASE_CREATE_GROUPS);
    }

}

private boolean checkDataBase(){

    SQLiteDatabase checkDB = null;

    try{
        String myPath = DATABASE_PATH + DATABASE_NAME;
        checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);

    }catch(SQLiteException e){

        //database does't exist yet.

    }

    if(checkDB != null){

        checkDB.close();

    }

    return checkDB != null ? true : false;
}

Answer 1

文档说明返回的游标对象在第一次输入之前定位。我认为首先在这种情况下将永远返回false。 result.moveToFirst（）？检查返回的条目数。

Answer 2

您是收到错误还是没有结果？您确定数据在数据库中吗？

Answer 3

您是否使用android_metadata表设置了sqlite数据库？请参阅that post，这可能有所帮助。对于我的应用程序，我正在使用该帖子中的数据库助手类，它就像一个魅力。

查询适用于SQLite浏览器，但不适用于Android SQlite

3 个答案: