Java 如何修复使我的应用程序崩溃的数据库问题？

我添加了一个新用户，但当我尝试登录时，它会使我的应用程序崩溃。它告诉我没有名称列。我们将非常感谢您的任何帮助。这是我的密码：

 public void onCreate(SQLiteDatabase db) {
    // TODO Auto-generated method stub
    db.execSQL(
            "create table users " +
                    "(id integer primary key, name text,password text,age integer)"
    );
    db.execSQL(
            "create table tasks " +
                    "(id integer primary key, name text, agemin integer,agemax integer,time integer)"
    );
}
public boolean insertUser (String name, String password, int age) {
    SQLiteDatabase db = this.getWritableDatabase();
    ContentValues contentValues = new ContentValues();
    contentValues.put("name", name);
    contentValues.put("password", password);
    contentValues.put("age", age);
    db.insert("users", null, contentValues);
    return true;
}

public boolean checkPassword(String name, String password) {
    int id = getUserIDByName(name);
    SQLiteDatabase db = this.getReadableDatabase();
    Cursor res =  db.rawQuery( "select password from users where id="+id+"", null );
    String pass = res.getString(1);
    return (password.equals(pass));
}

public int getUserIDByName(String name) {
    SQLiteDatabase db = this.getReadableDatabase();
    Cursor res =  db.rawQuery( "select id from users where name="+name+"", null );
    int id = res.getInt(1);
    return id;

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我建议如下，因为它可以防止sql注入

String query = "select id from users where name=?";
Cursor cursor = db.rawQuery(query, new String [] {name});

但如果您想使用原始查询，请确保在字符串值周围加引号

改变

Cursor res =  db.rawQuery( "select id from users where name="+name+"", null );

到

---

由于要在getUserIdbyName函数中比较名称，所以在查询中应该使用colun

public int getUserIDByName(String name) {
    SQLiteDatabase db = this.getReadableDatabase();
    Cursor res =  db.rawQuery( "select id from users where name='"+name+"'", null );
    int id = res.getInt(1);
    return id;
}

整数和数字数据类型在SQL中很容易比较，当涉及到字符串或文本类型时，有时会非常棘手且有点困难

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希望这对你有用

首先在名称变量周围使用引号：

Cursor res =  db.rawQuery( "select id from users where name = '"+ name + "'", null );

然后改为：

int id = res.getInt(0);

public boolean checkPassword(String name, String password) {
    int id = getUserIDByName(name);
    SQLiteDatabase db = this.getReadableDatabase();
    Cursor res =  db.rawQuery( "select password from users where id="+id+"", null );
    String pass = "";
    if (res.moveFirst())
        pass = res.getString(0);
    return (password.equals(pass));
}

public int getUserIDByName(String name) {
    SQLiteDatabase db = this.getReadableDatabase();
    Cursor res =  db.rawQuery( "select id from users where name='"+name+"'", null );
    int id = 0;
    if (res.moveFirst())
        id = res.getInt(0);
    return id;
}

这是：

String pass = res.getString(0);

游标列的索引基于0。 此外，还必须使用moveFirst检查光标是否提取了任何行。 因此，请改为：

int id = res.getInt(0);

public boolean checkPassword(String name, String password) {
    int id = getUserIDByName(name);
    SQLiteDatabase db = this.getReadableDatabase();
    Cursor res =  db.rawQuery( "select password from users where id="+id+"", null );
    String pass = "";
    if (res.moveFirst())
        pass = res.getString(0);
    return (password.equals(pass));
}

public int getUserIDByName(String name) {
    SQLiteDatabase db = this.getReadableDatabase();
    Cursor res =  db.rawQuery( "select id from users where name='"+name+"'", null );
    int id = 0;
    if (res.moveFirst())
        id = res.getInt(0);
    return id;
}

---

把你的事故日志贴出来。我照你说的做了，但还是不行。现在它告诉我索引-1被请求，大小为6，我做了你让我做的，但它仍然不起作用。现在它告诉我请求索引-1，大小为6