从Firebase检索时间戳返回键和值{sv = ServerValue.TimeStamp}

Question

我已经找到了一些关于从Firebase检索和转换时间戳的示例。只是因为我无法理解转换是如何工作的，它总是给我一个关键和值的输出，而不是正确的日期格式。我只是一个新手程序员，正在构建我的第一个移动应用程序。

这是我的模型类UserPost中的代码。

    public class UserPost {
    String postEmotion;
    String authorName;
    String userId;
    int postEmotion;
    String postDescription;
    HashMap<String, Object> dateCreated;


    public UserPost() {
    }



    public UserPost(String authorName, String userId, int postEmotion, String postDescription, HashMap<String,Object> dateCreated) {
        this.authorName = authorName;
        this.userId = userId;
        this.postEmotion = postEmotion;
        this.postDescription = postDescription;
        this.dateCreated = dateCreated;
        HashMap<String, Object> timestampNow = new HashMap<>();
        timestampNow.put("dateCreated", ServerValue.TIMESTAMP);
    }

    public String getAuthorName() { return authorName; }

    public String getUserId(){ return userId; }

    public int getPostEmotion() {
        return postEmotion;
    }

    public String getPostDescription() {
        return postDescription;
    }

    public HashMap<String, Object> getDateCreated() {
        //If there is a dateCreated object already, then return that
        if (dateCreated != null) {
            return dateCreated;
        }
        //Otherwise make a new object set to ServerValue.TIMESTAMP
        HashMap<String, Object> dateCreatedObj = new HashMap<String, Object>();
        dateCreatedObj.put("dateCreated", ServerValue.TIMESTAMP);

        //convertTime(getDateCreatedLong());
        return dateCreatedObj;
    }

    @Exclude
    public long getDateCreatedLong(){
        long timeStampvalue = (long)dateCreated.get("dateCreated");
        convertTime(timeStampvalue);
        return timeStampvalue;

    }

    public void convertTime(Long unixtime) {
        Date dateObject = new Date(unixtime);
        SimpleDateFormat dateFormatter = new SimpleDateFormat("dd-MM-yy hh:mm:ss");
        dateFormatter.format(dateObject);
    }

    @Exclude
    public Map<String, Object> toMap() {
        HashMap<String, Object> result = new HashMap<>();
        result.put("userId", userId);
        result.put("postEmotion", postEmotion);
        result.put("authorName",authorName);
        result.put("postDescription", postDescription);
        result.put("dateCreated", dateCreated);

        return result;
    }
}

NewsFeed.class我从Firebase检索数据。

mDatabase.child("post").addChildEventListener(new ChildEventListener() {
        public static final String TAG = "MARK's error";

        @Override
        public void onChildAdded(DataSnapshot dataSnapshot, String s) {
            if (dataSnapshot != null && dataSnapshot.getValue() != null) {
                try{
                    UserPost userPost = dataSnapshot.getValue(UserPost.class);

                    String author = userPost.getAuthorName();
                    String uid = userPost.getUserId();
                    int emo = userPost.getPostEmotion();
                    String post = userPost.getPostDescription();
                    HashMap<String,Object> date = userPost.getDateCreated();
                    data.add(new UserPost(author,uid,emo,post,date));


                } catch (Exception ex) {
                    Log.e(TAG, ex.getMessage());
                }
            }

            adapter.notifyDataSetChanged(); //to load the data if there's a value initially on my Firebase DB

        }

        @Override
        public void onChildChanged(DataSnapshot dataSnapshot, String s) {

        }

        @Override
        public void onChildRemoved(DataSnapshot dataSnapshot) {

        }

        @Override
        public void onChildMoved(DataSnapshot dataSnapshot, String s) {

        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });

保存用户帖子。

String key = mDatabase.child("post").push().getKey();
                UserPost userPost = new UserPost(author,uid,setemoticon,postData,mDate);
                Map<String, Object> postValues = userPost.toMap();

                Map<String, Object> childUpdates = new HashMap<>();
                childUpdates.put("/post/" + key,postValues);
                childUpdates.put("/user-post/" + uid + "/" + key, postValues);
                mDatabase.updateChildren(childUpdates);

                Toast.makeText(getActivity(),"PIN POSTED!", Toast.LENGTH_SHORT).show();

Final Output