将字符串传递给 DatabasHelper 并在查询中使用它来搜索两个表之间的平均值

Question

抱歉，我对此有点陌生。我正在使用 java 构建一个 android 应用程序。我正在尝试将两个字符串传递给我的 DatabaseHelper class 以查询我的数据库。这是我将字符串检索到数据库助手的方法。

private void retrieveDataFromSqlite(){

    String selectedYear = String.valueOf(dateViewer.getYear());
    String selectedMonth = String.valueOf(dateViewer.getMonth() +1);
    String selectedDay =  String.valueOf(dateViewer.getDayOfMonth());

    String date = (selectedYear) + '-' + (selectedMonth) + '-' + selectedDay;
    String email = textViewName.getText().toString();


    Data dataSetter = new Data();
    dataSetter.setDate(date);
    dataSetter.setEmail(email);

    String x;
    x = databaseHelper.viewData();

    textViewSugar.setText(x);
}

这是我的数据库助手。

public String viewData(){
    //String x = "No Data For That Date";
    SQLiteDatabase db = this.getReadableDatabase();
    Data dataGetter = new Data();
    String x = dataGetter.getEmail();

    //final String MY_QUERY = "SELECT AVG(data) FROM data INNER JOIN user ON data.email = user.user_email";
    db.close();
    return x;
}

我的 getter 和 setter 也有一个数据 class。 public class 数据 {

private int data_id;
private int userId;
private int data;
private String email;
private String date;

public int getData_id(){ return data_id; }
public void setData_id(int data_id){ this.data_id = data_id;}
public int getUserId(){ return userId;}
public void setUserId(int userId){ this.userId = userId;}
public int getData(){return data;}
public void setData(int data){ this.data = data;}
public String getEmail(){return email;}
public void setEmail(String email){ this.email = email;};
public String getDate(){return date;}
public void setDate(String date){this.date = date;}

}

Answer 1

您正在函数 viewData 中创建一个新的 Data 实例

public String viewData(){
Data dataGetter = new Data();
}

它与 retrieveDataFromSqlite 函数的数据对象没有关系。

无需在 viewData 函数中创建新的数据对象，只需传递数据获取器，然后从中获取值

public String viewData(Data dataGetter){
    //String x = "No Data For That Date";
    SQLiteDatabase db = this.getReadableDatabase();
    String x = dataGetter.getEmail();

    //final String MY_QUERY = "SELECT AVG(data) FROM data INNER JOIN user ON data.email = user.user_email";
    db.close();
    return x;
}

然后从 retrieveDataFromSqlite 函数传递数据，如

x = databaseHelper.viewData(dataSetter);

将字符串传递给 DatabasHelper 并在查询中使用它来搜索两个表之间的平均值

Passing String to DatabasHelper and using it in a query to search for an average between two tables

java

android

database

sqlite

helper