Question

我想随机获取随机ID然后我正在尝试获取WORDTR和WORDEN的索引但不能这样做。请帮助我。

public class DatabeseHelper  extends SQLiteOpenHelper {
public DatabeseHelper(Context c){
    super(c,"WORDS",null,1);

    SQLiteDatabase db =this.getWritableDatabase();

}

@Override
public void onCreate(SQLiteDatabase db) {
    String sql="create table WORDS(ID integer primary key autoincrement,WORDTR TEXT,WORDEN TEXT)";
    db.execSQL(sql);

}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)     {
    db.execSQL("DROP TABLE IF EXISTS WORDS");
    onCreate(db);
}

public Cursor getDataRandom(){

    SQLiteDatabase db = this.getWritableDatabase();

    Cursor cursor = db.rawQuery("select * from ID ORDER BY RANDOM() LIMIT 1 ",null);
    cursor.moveToFirst();

    int id = cursor.getInt(cursor.getColumnIndex("ID"));


    return cursor;

Answer 1

表名是＆＃34; WORDS＆＃34;当你创建表时。但是你试图从表名＆＃34; ID＆＃34;中获取数据。在任何地方都不存在。

正确的代码是

public Cursor getDataRandom(){

    SQLiteDatabase db = this.getWritableDatabase();

    Cursor cursor = db.rawQuery("select * from WORDS ORDER BY RANDOM() LIMIT 1 ",null);
    cursor.moveToFirst();

    int id = cursor.getInt(cursor.getColumnIndex("ID"));


    return cursor;
}

Answer 2

您在代码中遇到很多错误，请参阅以下带注释的代码

公共类DatabeseHelper扩展了SQLiteOpenHelper {

public DatabeseHelper(Context c){
    super(c,"WORDS",null,1);
   // SQLiteDatabase db =this.getWritableDatabase();

}

@Override
public void onCreate(SQLiteDatabase db) {
    String sql="create table WORDS(ID integer primarykey autoincrement,WORDTR TEXT,WORDEN TEXT)";
    db.execSQL(sql);

}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    db.execSQL("DROP TABLE IF EXISTS WORDS");
    onCreate(db);
}

选择随机数据。

    public Cursor getDataRandom(){

            SQLiteDatabase db = this.getWritableDatabase();

           // select * from WORDS not a ID
            Cursor cursor = db.rawQuery("select * from WORDS ORDER BY RANDOM() LIMIT 1 ",null);
            cursor.moveToFirst();

            // id is not used,not need to declare
            int id = cursor.getInt(cursor.getColumnIndex("ID"));


           // return a id not a cursor
            return cursor;
    }

Answer 3

public DatabeseHelper(Context c){
    super(c,"WORDS",null,1);

    SQLiteDatabase db =this.getWritableDatabase();

}

@Override
public void onCreate(SQLiteDatabase db) {
    String sql="CREATE TABLE IF NOT EXISTS " + WORDS+
    "( " +
    "ID INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL UNIQUE, " +
    "WORDTR  TEXT, WORDEN TEXT);";

    db.execSQL(sql);

}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    db.execSQL("DROP TABLE IF EXISTS WORDS");
    onCreate(db);
}

public int getDataRandom（）{

SQLiteDatabase db = this.getWritableDatabase();

    Cursor cursor = db.rawQuery("select * from WORDS ORDER BY RANDOM() LIMIT 1 ",null);
     if (cursor.moveToFirst()) {

    int id = cursor.getInt(cursor.getColumnIndex("ID"));

 } while (cursor.moveToNext());
    return id;

如何使用id获取索引？

3 个答案: