Question

我正在为俱乐部制作应用程序，应该记录会员出席情况。我在列表视图中无法正常使用它。

以下是数据库的一部分：

可能会有多项运动如空手道或某一天游泳。我希望会员在列表视图中出席。我会在一天之后尝试对其进行分区，但是现在我需要正确地获取数据。这是我制作的模型：

public class MemberAttendance {

private String day;
private HashMap<String, Object> attendedSport;


public MemberAttendance() {

}

public MemberAttendance(String day, HashMap<String, Object> attendedSport) {

    this.day = day;
    this.attendedSport = attendedSport;

}

public String getDay() {
    return day;
}

public void setDay(String day) {
    this.day = day;
}

public HashMap<String, Object> getAttendedSport() {
    return attendedSport;
}

public void setAttendedSport(HashMap<String, Object> attendedSport) {
    this.attendedSport = attendedSport;
}

}

这是适配器：

public class MemberAttendanceAdapter extends FirebaseListAdapter<MemberAttendance> {

public MemberAttendanceAdapter(Activity activity, Class<MemberAttendance> modelClass, int modelLayout, Query ref) {
    super(activity, modelClass, modelLayout, ref);
}

@Override
protected void populateView(View view, MemberAttendance memberAttendance, int i) {

    // Get values from firebase database
    String day = memberAttendance.getDay();

    HashMap<String, Object> hashMap = memberAttendance.getAttendedSport();
    String sport = (String) hashMap.get("attended");
    String date = (String) hashMap.get("timestamp");

    // Create views and assign values
    TextView dayTxtView = (TextView) view.findViewById(R.id.dayTxtView);
    dayTxtView.setText(day);

    TextView sportTxtView = (TextView) view.findViewById(R.id.sportTxtView);
    sportTxtView.setText(sport);

    TextView dateTxtView = (TextView) view.findViewById(R.id.dateTxtView);
    dateTxtView.setText(date);

}

}

这是我尝试设置适配器的方法：

        final FirebaseDatabase database = FirebaseDatabase.getInstance();

    final DatabaseReference attendanceRef = database.getReference()
           .child(Constants.MEMBERS_NODE).child(userID).child("attendance");

    attendanceAdapter = new MemberAttendanceAdapter(getActivity(), MemberAttendance.class,
            R.layout.attendance_list_item, attendanceRef);

    attendanceListView.setAdapter(attendanceAdapter);

到目前为止还没有工作，并且在使用HashMap.get（..）的对象引用上给出了空指针异常

String sport = (String) hashMap.get("attended");

感谢任何帮助。

Answer 1

我建议在HashMap内创建另一个对象AttendedSport作为变量而不是MemberAttendance，而Firebase将使用HashMap映射数据。 } populateView你可以得到像

这样的数据

memberAttendance.getAttendedSport().getSport()和memberAttendance.getAttendedSport().getTimeStamp()

我不保证它会解决您的问题，但我认为它不易出错。

Answer 2

您可能希望重构NoSQL数据库，如下所示：

member
---memberID
------attendance
---------attendance ID
------------attended
------------timestamp
------------date

例如：

member
---member1
------attendance
---------attendance1
------------soccer
------------14938372834
------------14-04-2017
---------attendance2
------------swimming
------------14938374323
------------14-04-2017

您不需要存储日期，因为use可以使用时间戳在Java中创建包含该信息的Date对象

Date date = new Date(timestamp);

使用此结构，您需要将POJO更改为：

public class MemberAttendance {

    private String attended;
    private long timestamp;


    public MemberAttendance() {

    }

    public MemberAttendance(String attended, long timestamp) {

        this.attended = attended;
        this.timestamp = timestamp;

    }

    public String getAttended() {
        return attended;
    }

    public void setAttended(String attended) {
        this.attended = attended;
    }

    public long getTimestamp() {
        return timestamp;
    }

    public void setTimestamp(long timestamp) {
        this.attendedSport = attendedSport;
    } 
}

然后，您可以使用相同的Firebase查询，并在适配器中进行以下更改：

public class MemberAttendanceAdapter extends FirebaseListAdapter<MemberAttendance> {

    public MemberAttendanceAdapter(Activity activity, Class<MemberAttendance> modelClass, int modelLayout, Query ref) {
        super(activity, modelClass, modelLayout, ref);
    }

    @Override
    protected void populateView(View view, MemberAttendance memberAttendance, int i) {

        String sport = memberAttendace.getAttended();
        Date date = new Date(memberAttendance.getTimestamp());

        // Create views and assign values
        TextView dayTxtView = (TextView) view.findViewById(R.id.dayTxtView);
        dayTxtView.setText(new SimpleDateFormat("dd-MM-yyyy").format(date););

        TextView sportTxtView = (TextView) view.findViewById(R.id.sportTxtView);
        sportTxtView.setText(sport);

        //I think you want to show the time here, not the date
        TextView dateTxtView = (TextView) view.findViewById(R.id.dateTxtView);
        dateTxtView.setText(new SimpleDateFormat("HH:mm:ss").format(date));

    }
}

修改：关于按日期查询出席情况的评论，请查看我在上述结构中所做的修改，然后使用Firebase查询，例如

ref.child("members")
   .child(<memberIdHere>)
   .child("attendance")
   .orderByChild("date")
   .equalTo(<yourDateHere>);

正确获取Firebase数据

2 个答案: