android.database.sqlite.SQLiteException:无此类列:user_id(代码1 SQLITE_ERROR): [英] android.database.sqlite.SQLiteException: no such column: user_id (code 1 SQLITE_ERROR):

问题描述

作为一名Android Studio初学者，我会遇到很多我无法发现的小错误，请让我知道我在做错什么，因为我以某种方式尝试了所有其他答案，但并没有得到更好的解决: )

being an Android Studio beginner i tend to get lots and lots of tiny errors i cannot find out, please let me know what I am doing wrong because I've tried all the other answers somehow and it doesn't get better :)

public class DatabaseHelper extends SQLiteOpenHelper{

    private static final int DATABASE_VERSION = 1;

    private static final String DATABASE_NAME = "UserManager.db";

    private static final String TABLE_USER = "user";

    private static final String COLUMN_USER_ID= "user_id";
    private static final String COLUMN_USER_NAME= "user_name";
    private static final String COLUMN_USER_EMAIL= "user_email";
    private static final String COLUMN_USER_PASSWORD= "user_password";

    private String CREATE_USER_TABLE = "CREATE TABLE " + TABLE_USER + "(" + 
    COLUMN_USER_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, "
    + COLUMN_USER_NAME + " TEXT," + COLUMN_USER_EMAIL + " TEXT," + 
    COLUMN_USER_PASSWORD + " TEXT" + ")";

    private String DROP_USER_TABLE = " DROP TABLE IF EXISTS " + TABLE_USER;

    public DatabaseHelper(Context context){

        super(context, DATABASE_NAME,null, DATABASE_VERSION);

    }

    @Override
    public void onCreate(SQLiteDatabase db){
        db.execSQL(CREATE_USER_TABLE);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion){
        db.execSQL(DROP_USER_TABLE);
        onCreate(db);
    }

    public void addUser(User user){
        SQLiteDatabase db= this.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put(COLUMN_USER_NAME, user.getName());
        values.put(COLUMN_USER_EMAIL, user.getEmail());
        values.put(COLUMN_USER_PASSWORD, user.getPassword());


        db.insert(TABLE_USER,null, values);
        db.close();


    }

    public boolean checkUser(String password, String email){
        String[] columns = {
                COLUMN_USER_ID
        };
        SQLiteDatabase db= this.getWritableDatabase();
        String selection = COLUMN_USER_EMAIL + " = ? " + "AND "+ COLUMN_USER_PASSWORD+" =? ";
        String[] selectionArgs = { email,password };

        Cursor cursor = db.query(TABLE_USER,
                columns,
                selection,
                selectionArgs,
                null,
                null,
                null);
        int cursorCount = cursor.getCount();
        cursor.close();
        db.close();

        if(cursorCount > 0){
            return true;
        }
        return false;
     }
}

我知道logcat让我知道这一点:

I know the logcat let me know this:

07-11 22:08:29.072 9071-9071/com.example.lavinia.sqllogin E/AndroidRuntime: 
FATAL EXCEPTION: main
Process: com.example.lavinia.sqllogin, PID: 9071
android.database.sqlite.SQLiteException: no such column: user_id (code 1 
SQLITE_ERROR): , while compiling: SELECT user_id FROM user WHERE user_email = 
?AND user_password =?

而且我找不到 user_id 的错误用法，我认为我使用得很好，并且我登录自己后该应用程序将停止运行. (该应用程序具有登录和注册活动-并且注册可以正常进行，但是在Login.activity中按登录"按钮会使应用程序崩溃)

And I can't find the wrong usage of user_id, I think I used it fine and the app will stop working after I Login myself. (the app has login and registration activities- and the registration works ok, but pressing the Login button in the Login.activity will make the app crash)

非常感谢您的支持:)如果需要，我将提供进一步的代码.

Thank you very much for you support :) If needed, I will provide with further code.

推荐答案

此问题可能是由于 我倾向于遇到很多细小的错误 关于onCreate方法的常见误解.

This issue is probably due to i tend to get lots and lots of tiny errors in conjunction with a common misconception regarding the onCreate method.

onCreate方法仅在数据库已创建且已实际创建时自动自动运行一次.它不会在每次运行该应用程序时运行.

The onCreate method automatically runs only once when the database is and has actually been created. It does not run every time the App is run.

因此，如果在onCreate方法中对结构(表和列)进行了编码/操作，则对结构(表和列)所做的任何更改(包括更正)都将不适用.

As such any changes (corrections included) to the structure (tables and columns) will not be applied if they are coded/actioned within the onCreate method.

开发最简单的解决方法是执行以下3项之一:-

When developing the easiest fix is to do one of the following 3:-

• 删除应用程序的数据(删除数据库，以便调用onCreate).
• 卸载应用程序(删除数据库，因此将调用onCreate).
• 如果onUpgrade方法将删除表，然后调用onCreate，以增加作为第4个参数传递给SQLIteOpenHelper子类(又称为DatabaseHelper类)的数据库版本号.

• delete the App's data (deletes the database so onCreate will be called).
• uninstall the App (deletes the database so onCreate will be called).
• if the onUpgrade method will drop the table(s) and then call onCreate , to increase the database version number as passed as the 4th parameter to the SQLIteOpenHelper sub-class (aka the DatabaseHelper class).

完成上述操作之一后，重新运行该应用程序.

After doing one of the above, rerun the App.

• 如果必须保留数据，则修复会更加复杂，但将基于使用ALTER TABLE语句.

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