如何在Android的另一个活动中从SQLite数据库中获取特定数据进行登录？

Question

这就是我创建数据库的方式。我想用密码取电子邮件进行登录。 SQL Anywhere数据库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类：

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， 在登录按钮点击

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"); 
    }