How to add like counter Android Studio Firebase

this is the database link 1can anybody help me to add a like counter to this.please please
it should display the no:of likes and decease it when like is taken back
my java code is below

private void onLikeClicked(View v) {
boolean isLiked = !btnLike.isSelected();
final String currentUserKey = User.currentKey();

DatabaseReference likes = FirebaseDatabase.getInstance().getReference().child(Const.kDataLikeKey);
DatabaseReference curLike = likes.child(mPostRef.getKey()).child(currentUserKey).child("liked");

// update Model
curLike.setValue(isLiked);

// update UI
btnLike.setSelected(isLiked);
}


This increment like count but doesn't decrements it i want it to get decremented when clicked back

1 Answer
1

Your question is not entirely clear but if you are trying to make a functionality like social media post where users can like and unlike a post the this can help.

Data Structure

Post-> postId -> likes -> 1
...


You can divide it in three parts:

To display number of likes for a post , postId & current user, userId1, has liked your post or not

postId

userId1

public void displayNumberOfLikes(String postId, String currentUserId){
DatabaseReference likesRef = FirebaseDatabase.getInstance().getReference().child('Post').child(postId);
likesRef.addValueEventListener(new ValueEventListener(){
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
if(dataSnapshot.exists()){
long numOfLikes = dataSnapshot.child("likes").getValue(Long.class);
//Populate numOfLikes on post i.e. textView.setText(""+numOfLikes)
//This is to check if the user has liked the post or not
btnLike.setSelected(dataSnapshot.hasChild(userId));
}
}

@Override
public void onCancelled(DatabaseError databaseError) {

}
});
}


On Like Clicked

public void onLikeClicked(View v, String postId, String userId){
DatabaseReference likesRef = FirebaseDatabase.getInstance().getReference().child('Post').child(postId).child("likes");
likesRef.addListenerForSingleValueEvent(new ValueEventListener(){
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
long numLikes = 0;
if(dataSnapshot.exists()){
numLikes = dataSnapshot.getValue(Long.class);
}
boolean isLiked = btnLike.isSelected();
if(isLiked){
//If already liked then user wants to unlike the post
likesRef.set(numLikes-1);
}else {
//If not liked already then user wants to like the post
likesRef.set(numLikes+1);
}
}

@Override
public void onCancelled(DatabaseError databaseError) {

}
});
}


This way you can make your user like and unlike a post and display total number of likes.
Hope it helps!

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