[FIXED] Using ServerValue.TIMESTAMP in my Android App

Issue

I have read lots of stackoverflow questions related to

ServerValue.TIMESTAMP

but I can't figure out how to use it in my app.

I need to get the timeStamp of the creation of a post. The timeStamp should be added to the same place as with uid , author etc. of the post.

Code snippet which writes the post the firebase database:

 private void writeNewPost(String userId, String username, String title, String body) {
    // Create new post at /user-posts/$userid/$postid and at
    // /posts/$postid simultaneously
    String key = mDatabase.child("posts").push().getKey();
    Post post = new Post(userId, username, title, body);
    Map<String, Object> postValues = post.toMap();

    Map<String, Object> childUpdates = new HashMap<>();
    childUpdates.put("/posts/" + key, postValues);
    childUpdates.put("/user-posts/" + userId + "/" + key, postValues);

    mDatabase.updateChildren(childUpdates);
}

My Post.java file

@IgnoreExtraProperties
public class Post {

public String uid;
public String author;
public String title;
public String body;
public int starCount = 0;
public Map<String, Boolean> stars = new HashMap<>();
public Long timeStamp;

public Post() {
    // Default constructor required for calls to DataSnapshot.getValue(Post.class)
}

public Post(String uid, String author, String title, String body) {
    this.uid = uid;
    this.author = author;
    this.title = title;
    this.body = body;
}

// [START post_to_map]
@Exclude
public Map<String, Object> toMap() {
    HashMap<String, Object> result = new HashMap<>();
    result.put("uid", uid);
    result.put("author", author);
    result.put("title", title);
    result.put("body", body);
    result.put("starCount", starCount);
    result.put("stars", stars);

    return result;
}
// [END post_to_map]

}

How should I use

ServerValue.TIMESTAMP 

in my code to get the time of creation of post.

Solution

ServerValue.TIMESTAMP is simply a placeholder value. When the Firebase server processes an update request and finds ServerValue.TIMESTAMP as a value, it replaces it with the current server clock.

In your writeNewPost() method you could add a line to set the creation time:

Map<String, Object> postValues = post.toMap();
postValues.put("timeStamp", ServerValue.TIMESTAMP);

If you use Post.toMap() only to create posts, and not for updates, you could put a similar statement there instead of in writeNewPost().

Answered By - Bob Snyder
Answer Checked By - Robin (JavaFixing Admin)