Java 时间戳方法'；SimpleDataFormat'；无法从数据库中检索

我遇到的问题是，

时间戳

没有像下面在Firebase中看到的那样保存。在

Posts

no

timestamp

child下。有人能解释一下为什么会这样吗

我真的很感激有人看我一眼，告诉我我做错了什么

下面是

时间戳的代码
PostAdapter.java
，
PostActivity.java
，以及
Post.java
模型类


PostActivity.java


    package com.e.events;

    public class PostActivity extends AppCompatActivity {

        Uri imageUri;
        String myUrl = "";
        StorageTask uploadTask;
        StorageReference storageReference;

        ImageView close, post_checkmark, image_added;
        String description, text_event, text_location, text_date_time;
        EditText txt_event, txt_description, txt_location, txt_date_time;

        private String postId;
        private String postImage;
        private String publisher;
        private Map<String, String> timestamp;

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_post);

            close = findViewById(R.id.close);
            post_checkmark = findViewById(R.id.post_checkmark);
            image_added = findViewById(R.id.new_image_added);
            txt_description = findViewById(R.id.description);
            txt_event = findViewById(R.id.text_event);
            txt_location = findViewById(R.id.text_location);
            txt_date_time = findViewById(R.id.text_date_time);

            storageReference = FirebaseStorage.getInstance().getReference("posts");

            close.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    startActivity(new Intent(PostActivity.this, MainActivity.class));
                    finish();
                }
            });

            post_checkmark.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    uploadImage();
                }
            });

            CropImage.activity()
                    .setAspectRatio(1, 1)
                    .start(PostActivity.this);
        }

    private void saveTimestamp() {
            Log.d(TAG, "saveTimestamp: getting timestamp");
            FirebaseDatabase database = FirebaseDatabase.getInstance();
            String key = database.getReference().child("Posts").push().getKey();

            Post post = new Post(description, postId, postImage, publisher, timestamp, text_event, text_location, text_date_time);
            database.getReference("Posts").child(key).setValue(post);

            DatabaseReference reference = FirebaseDatabase.getInstance().getReference();
            Map<String, Object> map = new HashMap<>();
            map.put("timestamp", ServerValue.TIMESTAMP);
            reference.child("Posts").setValue(map);
        }
    }



    package com.e.events.Adapter;

    public class PostAdapter extends RecyclerView.Adapter<PostAdapter.ViewHolder> {

        public Context mContext;
        public List<Post> mPost;

        private FirebaseUser firebaseUser;

        public PostAdapter(Context mContext, List<Post> mPost) {
            this.mContext = mContext;
            this.mPost = mPost;
        }

        @NonNull
        @Override
        public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
            View view = LayoutInflater.from(mContext).inflate(R.layout.post_item, parent, false);
            return new PostAdapter.ViewHolder(view);
        }

        @Override
        public void onBindViewHolder(@NonNull final ViewHolder holder, int position) {

            firebaseUser = FirebaseAuth.getInstance().getCurrentUser();
            final Post post = mPost.get(position);

            Glide.with(mContext).load(post.getPostimage())
                    .apply(new RequestOptions().placeholder(R.drawable.placeholderimg))
                    .into(holder.post_image);
    if ("".equals(post.getTimestamp())) {
                Log.i(TAG, post.getTimestamp().toString());
                holder.timestamp.setVisibility(View.GONE);
            } else {
                holder.timestamp.setVisibility(View.VISIBLE);
                holder.timestamp.setText(post.getTimestamp().toString());
            }

    public class ViewHolder extends RecyclerView.ViewHolder {

            public TextView timestamp;

            public ViewHolder(@NonNull View itemView) {
                super(itemView);


                timestamp = itemView.findViewById(R.id.timestamp);

            }

            //Set words for the timestamp "Today" or "___ days ago"
            private void setupWidgets() {
                String timestampDifference = getTimestampDifference();
                if (!timestampDifference.equals("0")) {
                    timestamp.setText(timestampDifference + " days ago");
                } else {
                    timestamp.setText("Today");
                }
            }

            //Timestamp
            private String getTimestampDifference() {
                Log.d(TAG, "getTimestampDifference: getting timestamp difference");

                String difference = "";
                Calendar calendar = Calendar.getInstance();
                SimpleDateFormat simpleDateFormat = new SimpleDateFormat("dd-MMM-yyyy'T'HH:mm:ss'Z'", Locale.US);
                simpleDateFormat.setTimeZone(TimeZone.getTimeZone("America/Chicago"));
                Date today = calendar.getTime();
                simpleDateFormat.format(today);
                Date timestamp;
                final String dateTime = simpleDateFormat.format(calendar.getTime());
                try {
                    timestamp = simpleDateFormat.parse(dateTime);
                    difference = String.valueOf(Math.round(((today.getTime() - timestamp.getTime()) / 1000 / 60 / 60 / 24)));
                } catch (ParseException e) {
                    difference = "0";
                }
                return difference;
            }
        }

        private void getTimestamp() {
            DatabaseReference reference = FirebaseDatabase.getInstance().getReference();

            reference.addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(DataSnapshot snapshot) {
                    Long timestamp = (Long) snapshot.getValue();
                    System.out.println(timestamp);
                }

                @Override
                public void onCancelled(DatabaseError databaseError) {

                }
            });
        }



包com.e.events；
公共类PostActivity扩展了AppCompative活动{
Uri-imageUri；
字符串myUrl=“”；
StorageTask上传任务；
StorageReference-StorageReference；
ImageView关闭、post_复选标记、图像_添加；
字符串描述、文本事件、文本位置、文本日期时间；
EditText txt_事件、txt_描述、txt_位置、txt_日期_时间；
私人字符串posted；
私有字符串后期图像；
私有字符串发布器；
私有映射时间戳；
@凌驾
创建时受保护的void（Bundle savedInstanceState）{
super.onCreate（savedInstanceState）；
setContentView（R.layout.activity_post）；
关闭=findViewById（R.id.close）；
post_复选标记=findViewById（R.id.post_复选标记）；
添加的图像=findviewbyd（R.id.new\u添加的图像）；
txt_description=findviewbyd（R.id.description）；
txt_事件=findViewById（R.id.text_事件）；
txt_location=findviewbyd（R.id.text_location）；
txt_date_time=findviewbyd（R.id.text_date_time）；
storageReference=FirebaseStorage.getInstance（）.getReference（“posts”）；
close.setOnClickListener（新视图.OnClickListener（）{
@凌驾
公共void onClick（视图v）{
startActivity（新意图（PostActivity.this，MainActivity.class））；
完成（）；
}
});
post_checkmark.setOnClickListener（新视图.OnClickListener（）{
@凌驾
公共void onClick（视图v）{
上传图像（）；
}
});
CropImage.activity（）
.setAspectRatio（1,1）
.启动（后活动。此）；
}
私有void saveTimestamp（）{
Log.d（标记“saveTimestamp:gettingtimestamp”）；
FirebaseDatabase=FirebaseDatabase.getInstance（）；
String key=database.getReference（）.child（“Posts”）.push（）.getKey（）；
Post Post=新发布（描述、发布ID、发布图像、发布者、时间戳、文本事件、文本位置、文本日期时间）；
database.getReference（“Posts”）.child（key）.setValue（post）；
DatabaseReference=FirebaseDatabase.getInstance（）.getReference（）；
Map Map=newhashmap（）；
map.put（“timestamp”，ServerValue.timestamp）；
参考.child（“Posts”）.setValue（map）；
}
}

PostAdapter.java


    package com.e.events;

    public class PostActivity extends AppCompatActivity {

        Uri imageUri;
        String myUrl = "";
        StorageTask uploadTask;
        StorageReference storageReference;

        ImageView close, post_checkmark, image_added;
        String description, text_event, text_location, text_date_time;
        EditText txt_event, txt_description, txt_location, txt_date_time;

        private String postId;
        private String postImage;
        private String publisher;
        private Map<String, String> timestamp;

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_post);

            close = findViewById(R.id.close);
            post_checkmark = findViewById(R.id.post_checkmark);
            image_added = findViewById(R.id.new_image_added);
            txt_description = findViewById(R.id.description);
            txt_event = findViewById(R.id.text_event);
            txt_location = findViewById(R.id.text_location);
            txt_date_time = findViewById(R.id.text_date_time);

            storageReference = FirebaseStorage.getInstance().getReference("posts");

            close.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    startActivity(new Intent(PostActivity.this, MainActivity.class));
                    finish();
                }
            });

            post_checkmark.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    uploadImage();
                }
            });

            CropImage.activity()
                    .setAspectRatio(1, 1)
                    .start(PostActivity.this);
        }

    private void saveTimestamp() {
            Log.d(TAG, "saveTimestamp: getting timestamp");
            FirebaseDatabase database = FirebaseDatabase.getInstance();
            String key = database.getReference().child("Posts").push().getKey();

            Post post = new Post(description, postId, postImage, publisher, timestamp, text_event, text_location, text_date_time);
            database.getReference("Posts").child(key).setValue(post);

            DatabaseReference reference = FirebaseDatabase.getInstance().getReference();
            Map<String, Object> map = new HashMap<>();
            map.put("timestamp", ServerValue.TIMESTAMP);
            reference.child("Posts").setValue(map);
        }
    }



    package com.e.events.Adapter;

    public class PostAdapter extends RecyclerView.Adapter<PostAdapter.ViewHolder> {

        public Context mContext;
        public List<Post> mPost;

        private FirebaseUser firebaseUser;

        public PostAdapter(Context mContext, List<Post> mPost) {
            this.mContext = mContext;
            this.mPost = mPost;
        }

        @NonNull
        @Override
        public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
            View view = LayoutInflater.from(mContext).inflate(R.layout.post_item, parent, false);
            return new PostAdapter.ViewHolder(view);
        }

        @Override
        public void onBindViewHolder(@NonNull final ViewHolder holder, int position) {

            firebaseUser = FirebaseAuth.getInstance().getCurrentUser();
            final Post post = mPost.get(position);

            Glide.with(mContext).load(post.getPostimage())
                    .apply(new RequestOptions().placeholder(R.drawable.placeholderimg))
                    .into(holder.post_image);
    if ("".equals(post.getTimestamp())) {
                Log.i(TAG, post.getTimestamp().toString());
                holder.timestamp.setVisibility(View.GONE);
            } else {
                holder.timestamp.setVisibility(View.VISIBLE);
                holder.timestamp.setText(post.getTimestamp().toString());
            }

    public class ViewHolder extends RecyclerView.ViewHolder {

            public TextView timestamp;

            public ViewHolder(@NonNull View itemView) {
                super(itemView);


                timestamp = itemView.findViewById(R.id.timestamp);

            }

            //Set words for the timestamp "Today" or "___ days ago"
            private void setupWidgets() {
                String timestampDifference = getTimestampDifference();
                if (!timestampDifference.equals("0")) {
                    timestamp.setText(timestampDifference + " days ago");
                } else {
                    timestamp.setText("Today");
                }
            }

            //Timestamp
            private String getTimestampDifference() {
                Log.d(TAG, "getTimestampDifference: getting timestamp difference");

                String difference = "";
                Calendar calendar = Calendar.getInstance();
                SimpleDateFormat simpleDateFormat = new SimpleDateFormat("dd-MMM-yyyy'T'HH:mm:ss'Z'", Locale.US);
                simpleDateFormat.setTimeZone(TimeZone.getTimeZone("America/Chicago"));
                Date today = calendar.getTime();
                simpleDateFormat.format(today);
                Date timestamp;
                final String dateTime = simpleDateFormat.format(calendar.getTime());
                try {
                    timestamp = simpleDateFormat.parse(dateTime);
                    difference = String.valueOf(Math.round(((today.getTime() - timestamp.getTime()) / 1000 / 60 / 60 / 24)));
                } catch (ParseException e) {
                    difference = "0";
                }
                return difference;
            }
        }

        private void getTimestamp() {
            DatabaseReference reference = FirebaseDatabase.getInstance().getReference();

            reference.addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(DataSnapshot snapshot) {
                    Long timestamp = (Long) snapshot.getValue();
                    System.out.println(timestamp);
                }

                @Override
                public void onCancelled(DatabaseError databaseError) {

                }
            });
        }



包com.e.events.Adapter；
公共类PostAdapter扩展了RecyclerView.Adapter{
公共语境；
公开名单；
私有FirebaseUser FirebaseUser；
公共邮政适配器（上下文mContext、列表mPost）{
this.mContext=mContext；
this.mPost=mPost；
}
@非空
@凌驾
public ViewHolder onCreateViewHolder（@NonNull ViewGroup parent，int viewType）{
视图=LayoutFlater.from（mContext）。充气（R.layout.post_项，父项，false）；
返回新的PostAdapter.ViewHolder（视图）；
}
@凌驾
public void onBindViewHolder（@NonNull final ViewHolder，int位置）{
firebaseUser=FirebaseAuth.getInstance（）.getCurrentUser（）；
最终Post Post=mPost.get（位置）；
Glide.with（mContext.load）（post.getPostimage（））
.apply（新的RequestOptions（）.placeholder（R.drawable.placeholder img））
.into（保持架、post_图像）；
如果（“.equals（post.getTimestamp（）））{
Log.i（标记，post.getTimestamp（）.toString（））；
holder.timestamp.setVisibility（View.GONE）；
}否则{
holder.timestamp.setVisibility（View.VISIBLE）；
holder.timestamp.setText（post.getTimestamp（）.toString（））；
}
公共类ViewHolder扩展了RecyclerView.ViewHolder{
公共文本视图时间戳；
公共视图持有者（@NonNull View itemView）{
超级（项目视图）；
timestamp=itemView.findviewbyd（R.id.timestamp）；
}
//为时间戳“今天”或“几天前”设置单词
私有void setupWidgets（）{
字符串timestampDifference=getTimestampDifference（）；
如果（！timestampDifference.equals（“0”））{
timestamp.setText（timestampDifference+“天以前”）；
}否则{
timestamp.setText（“今天”）；
}
}
//时间戳
私有字符串getTimestampDifference（）{
d（标记“getTimestampDifference:getting timestamp difference”）；
字符串差=”；
日历=Calendar.getInstance（）；
SimpleDataFormat SimpleDataFormat=新的SimpleDataFormat（“dd-MMM-yyyy'T'HH:mm:ss'Z'，Locale.US”）；
SimpleDataFormat.setTimeZone（TimeZone.getTimeZone（“美国/芝加哥”）；
Date today=calendar.getTime（）；
SimpleDataFormat.format（今天）；
日期时间戳；
最终字符串dateTime=simpleDataFormat.format（calendar.getTime（））；
试一试{
timest
Posts post = new Post(description,postId,postImage,publisher,timestamp);
db.getReference("Posts").child(key).setValue(post);

DatabaseReference reference = FirebaseDatabase.getInstance().getReference();
                Map map = new HashMap();
                map.put("timestamp", ServerValue.TIMESTAMP);
                reference.child("Posts").child(key). updateChildren(map)