如何使用SQLite中的子列填充複雜列表？

Question

我有一個列表的結構，我想從數據庫中填充。我已經映射了所有表格和插入方法。然而，我不知道什麼是最好的方法來獲取所有這些數據並填充我的Java對象。我有這樣的結構：

public class DailySchedule { 
    private long id; 
    private List<Task> tasks; 
    private List<Plan> plans; 
} 

public class Task { 
    private long id; 
    private long duration; 
    private String description; 
    private Date date; 
} 

public class Plan { 
    private long id; 
    private String description; 
    private Date date; 
    private List<User> users; 
} 

public class User { 
    private long id; 
    private String name; 
} 

我應該創建一個巨大的INNERJOIN和獲取所有數據（包括重複的信息），並嘗試填充Java對象，或者我應該從每個表得到所有的ID和執行在Java中循環（使用遊標）並通過ID執行Selects並填充表？

Answer 1

我假設你有如下表

• daily_schedule
• 任務
• 計劃
• 用戶

代碼

public List<DailySchedule> getDailySchedules(){ 
    SQLiteDatabase db = getReadableDataBase(); 
    Cursor dailyScheduleCursor = db.rawQuery(「Select * from daily_schedule 」); 
    List<DailySchedule> all = new ArrayList<>(); 
    While(dailyScheduleCursor.next()){ 
     DailySchedule dailySchedule = new DailySchedule(); 
     dailySchedule.setId(dailyScheduleCursor.getLong(0)); 
     dailySchedule.setTasks(getTasks(dailyScheduleCursor.getLong(0))); 
     dailySchedule.setPlans(getTasks(dailyScheduleCursor.getLong(0))); 
     all.add(dailySchedule); 
     } 
    db.close(); 
} 
public List<Task> getTasks(int id){ 
    SQLiteDatabase db = getReadableDataBase(); 
    Cursor taskCursor = db.rawQuery(「Select * from tasks where id =’」+id+」’ 」); 
    List<Task> all = new ArrayList<>(); 
    While(taskCursor.next()){ 
     Task task = new task(); 
     task.setId(taskCursor.getLong(0)); 
     // set other attributes  
     all.add(task); 
    } 
    db.close(); 
    return all; 


} 

public List<Plan> getPlan(int id){ 

    getUser(id);// get all plans 
    // set user 
    return plans; 
} 
public User(int id){ 
     //create user from data 
    return user; 
} 

然後從某處撥打getDailySchedules()。

注意：如果你想看到你的SQLite DATABSE內容，請使用 AndroidDBvieweR