如何在另一個活動中從 SQLite 數據庫中獲取特定數據以在 Android 中登錄？

Question

這就是我創建數據庫的方式。我想獲取帶有登錄密碼的電子郵件。

SQLiteDatabase db = openOrCreateDatabase("MyDBC", MODE_PRIVATE, null);

        db.execSQL("CREATE TABLE IF NOT EXISTS MyTable(DB_collegename VARCHAR,DB_collegecode int,DB_email VARCHAR,DB_phoneno int,DB_pass VARCHAR,DB_colgcity VARCHAR,DB_collegecountry VARCHAR);");

        db.execSQL("INSERT INTO MyTable VALUES('" + collegename + "','" + collegecode + "','" + email + "','" + phoneno + "','" + colgcity + "','" + colgcountry + "');");
        db.close();

Answer 1

在 databaseHelper 類中：

   public boolean check_user(String u_name, String u_pwd) {

        SQLiteDatabase db = this.getWritableDatabase();

        String select = "SELECT * FROM " + TABLE_USER+ " WHERE " + KEY_USERNAME + "='" + u_name + "' AND " + KEY_PASSWORD + "='" + u_pwd + "'";

        Cursor c = db.rawQuery(select, null);

        if (c.moveToFirst()) {
            int key_id = c.getInt(c.getColumnIndex(KEY_ID));
            Log.d(TAG, "@@ user Login ID :"+key_id);

            return true;
        }

        if(c!=null)
          c.close();
        db.close();
        return false;
    }

在 login.java 中，點擊登錄按鈕

    DataBaseHelper db = new DataBaseHelper(mContext);
    boolean value = db.check_user(et_username.getText().toString().trim(), et_pwd.getText().toString().trim(), mContext);
    if (value) 
    {
        Log.d("TAG","User exits");
    } else {
        Log.d("TAG","User not exits");
    }