Android - 如何按日期对arrayList进行排序？

问题描述

我正在尝试按日期对 arrayList 进行排序。我每次收到通知时都会将日期存储在Firebase上，并从那里检索。我正在使用 Collections.sort 但我不知道如何实现我的代码，因为我的日期格式以字符串格式的数字开头，如2017年7月12日at 12:00 AM。

I'm trying to sort my arrayList by date. I stored the date on Firebase each time I receive a notification and is retrieved from there. I'm using Collections.sort but I don't know how to implement onto my codes as my date format starts with a number in a string format like "12 Jul 2017 at 12:00am".

我在stackoverflow上看到了一些这样的例子，但我不知道如何让它在我的情况下工作。我将在下面发布截图和我的代码。

I've seen some examples of this on stackoverflow but I don't know how to make it work in my case. I will post screenshots and my codes below.

日期未排序。

NotificationFragment.java

public class NotificationFragment extends Fragment {
        prepareNotification1();
        sortDate();
        return v;
    }

       private void prepareNotification1() {
            FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
            String userID = user.getUid();

  mRef.child("customers").child(userID).child("Notification").addChildEventListener(new ChildEventListener() {
            @Override
            public void onChildAdded(DataSnapshot dataSnapshot, String s) {
                    Notification menu = dataSnapshot.getValue(Notification.class);
                    notificationList.add(menu);
                mAdapter.notifyDataSetChanged();
            }
 });
    }

    public void sortDate() {
        Collections.sort(notificationList, new Comparator<Notification>() {
            @Override
            public int compare(Notification lhs, Notification rhs) {
                return lhs.getDate().compareTo(rhs.getDate());
            }
        });
        mAdapter = new NotificationAdapter(getContext(), notificationList);
        mRecyclerView.setAdapter(mAdapter);
    }
}

MyFirebaseMessagingService.java

public class MyFirebaseMessagingService extends FirebaseMessagingService {
@Override
    public void onMessageReceived(RemoteMessage remoteMessage) {
        Calendar cal = Calendar.getInstance();

        String currentDateTimeString = DateFormat.getDateInstance().format(new Date());

        SimpleDateFormat df = new SimpleDateFormat("hh:mm a");
        String currentTime = df.format(cal.getTime());

        String notificationTime = currentDateTimeString + " at " + currentTime;

        Notification newNotification = new Notification(remoteMessage.getData().get("body"), notificationTime);
        mRef.child("customers").child(userID).child("Notification").push().setValue(newNotification);
}

Notification.java

public class Notification {
    private String message;
    private String date;


    public Notification(){
    }

    public Notification(String message, String date){
        this.message = message;
        this.date = date;
    }

    public String getDate() {
        return date;
    }

    public void setDate(String date) {
        this.date = date;
    }

    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }
}

推荐答案

考虑将日期存储在通知中作为长（unix时间）或日期（ LocalDateTime 如果您正在使用Java 8支持）并仅在将其显示为UI时将其格式化为String。

Consider storing the date in Notification as a long (unix time) or a Date (LocalDateTime if you're using Java 8 support) and formatting it as a String only when displaying it to the UI.

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