Bdtjtk

I want to programm a ChatApp with Firebase. Right now I am displaying the Users I chat with. But now I want them to be sorted by a Date String I am using:
For Example: 21-06-2017 17:20. It should be sorted from the latest Time to the earliest Time.

My Adapter:

public class ChatAdapter extends ArrayAdapter<String> {



private Activity context;

private List<Chats> chatsList = new ArrayList<>();



public ChatAdapter(Activity context, List<Chats> chatsList) {

    super(context, R.layout.abc_main_chat_item);

    this.context = context;

    this.chatsList = chatsList;

}



@Override

public View getView(final int position, final View convertView, ViewGroup parent) {

    LayoutInflater inflater = context.getLayoutInflater();

    View listViewItem = inflater.inflate(R.layout.abc_main_chat_item, null, true);



    TextView tvusername = (TextView) listViewItem.findViewById(R.id.group_name);

    TextView tvuid = (TextView) listViewItem.findViewById(R.id.useruid);

    TextView tvlastmessage = (TextView) listViewItem.findViewById(R.id.latestMessage);

    TextView tvlastmessagetime = (TextView) listViewItem.findViewById(R.id.latestMessageTime);

    ImageView ivphoto = (ImageView) listViewItem.findViewById(R.id.profileImg);



    tvusername.setText(chatsList.get(position).getUsername());

    tvlastmessage.setText(chatsList.get(position).getLastMessage());

    tvlastmessagetime.setText(chatsList.get(position).getLastMessageTime());

    tvuid.setText(chatsList.get(position).getUseruid());

    Picasso.with(getContext()).load(chatsList.get(position).getPhotoURL()).placeholder(R.drawable.ic_person_grey_round).into(ivphoto);



    listViewItem.setOnClickListener(new View.OnClickListener() {

        @Override

        public void onClick(View v) {

            Intent i = new Intent(context, Chat_Room.class);

            i.putExtra("room_name", chatsList.get(position).getUsername());

            i.putExtra("room_uid", chatsList.get(position).getUseruid());

            context.startActivity(i);



        }

    });



    listViewItem.setOnLongClickListener(new View.OnLongClickListener() {

        @Override

        public boolean onLongClick(View v) {

            final Dialog dialog = new Dialog(context);

            dialog.setContentView(R.layout.abcd_listview_alertdia_layout);

            ArrayList<String> list_of_chats = new ArrayList<>();

            final ArrayAdapter<String> arrayAdapter;

            arrayAdapter = new ArrayAdapter<String>(context, android.R.layout.simple_list_item_1, list_of_chats);



            list_of_chats.add(0, "Chatverlauf mit "+ chatsList.get(position).getUsername()+" löschen?");

            list_of_chats.add(1, "Profil von "+chatsList.get(position).getUsername()+" anschauen");

            arrayAdapter.notifyDataSetChanged();

            final ListView lv = (ListView) dialog.findViewById(R.id.lv);

            lv.setAdapter(arrayAdapter);

            lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {

                @Override

                public void onItemClick(AdapterView<?> parent, View view, final int position2, long id) {

                    if (position2 == 0) {

                        dialog.dismiss();

                        AlertDialog.Builder alert = new AlertDialog.Builder(context);

                        alert.setTitle("Chatverlauf mit "+chatsList.get(position).getUsername()+" löschen?")

                                .setMessage("Du kannst das Löschen nicht rückgängig machen. Bist du dir sicher?")

                                .setNegativeButton("Abbrechen", new DialogInterface.OnClickListener() {

                                    @Override

                                    public void onClick(DialogInterface dialog, int which) {

                                        dialog.cancel();

                                    }

                                })

                                .setPositiveButton("OK", new DialogInterface.OnClickListener() {

                                    @Override

                                    public void onClick(DialogInterface dialog, int which) {

                                        FirebaseDatabase.getInstance().getReference().child("chats").child("userchats").child(FirebaseAuth.getInstance().getCurrentUser().getUid()).child(chatsList.get(position).getUseruid()).setValue(null);

                                        FirebaseDatabase.getInstance().getReference().child("chats").child("users").child(FirebaseAuth.getInstance().getCurrentUser().getUid()).child("messages").child(chatsList.get(position).getUseruid()).setValue(null);

                                    }

                                }).setCancelable(true)

                                .show();

                        lv.setAdapter(arrayAdapter);

                        arrayAdapter.notifyDataSetChanged();

                    }

                    if (position2 == 1) {

                        Intent intent = new Intent(context, ViewContact.class);

                        intent.putExtra("useruid", chatsList.get(position).getUseruid());

                        context.startActivity(intent);

                    }

                }

            });

            dialog.show();

            return true;

        }

    });



    ivphoto.setOnClickListener(new View.OnClickListener() {

        @Override

        public void onClick(View v) {

            final Dialog dialog = new Dialog(context);

            dialog.setContentView(R.layout.abcd_profile_pic_dialog_layout);

            ImageView imageView = (ImageView) dialog.findViewById(R.id.alertImage);

            TextView textView = (TextView)dialog.findViewById(R.id.alertdialogtv);

            ImageView message = (ImageView)dialog.findViewById(R.id.alertMessage);

            ImageView profile = (ImageView)dialog.findViewById(R.id.alertProfile);

            profile.setOnClickListener(new View.OnClickListener() {

                @Override

                public void onClick(View v) {

                    Intent intent = new Intent(context, ViewContact.class);

                    intent.putExtra("useruid", chatsList.get(position).getUseruid());

                    context.startActivity(intent);

                    dialog.dismiss();

                }

            });

            message.setOnClickListener(new View.OnClickListener() {

                @Override

                public void onClick(View v) {

                    Intent intent = new Intent(getContext(), Chat_Room.class);

                    intent.putExtra("room_name", chatsList.get(position).getUsername());

                    intent.putExtra("room_uid", chatsList.get(position).getUseruid());

                    context.startActivity(intent);

                }

            });

            Picasso.with(getContext()).load(chatsList.get(position).getPhotoURL()).placeholder(R.drawable.ic_person_grey_round).into(imageView);

            textView.setText(chatsList.get(position).getUsername());

            dialog.setCancelable(true);

            dialog.show();

        }

    });



    return  listViewItem;

}

This is how i got my ArrayLists:

`for(DataSnapshot snapshot : dataSnapshot.getChildren()){

                    username.add(snapshot.child("roomname").getValue().toString());

                    photoURL.add(snapshot.child("photoURL").getValue().toString());

                    lastmessage.add(snapshot.child("lastMessage").getValue().toString());

                    lastmessagetime.add(snapshot.child("lastMessageTime").getValue().toString());

                    useruid.add(snapshot.child("userUiD").getValue().toString());

                }



                ChatAdapter chatAdapter = new ChatAdapter(getActivity(), username, useruid, photoURL, lastmessage, lastmessagetime);

                listView.setAdapter(chatAdapter);`

But how can I pass it as a List ??
How can I add them to the list?

Is it even possible to sort it?

I hope you Guys can help me :)
Thanks.

This is of course possible.
But first, your data structure looks weird and unpractical.

Your messages are passed in single arrays which makes it quite complicated:

ArrayList<String> username, ArrayList<String> useruid, ArrayList<String> photoURL, ArrayList<String> lastmessage, ArrayList<String> lastmessagetime

Better would be to have a list of Messageobjects, where a message object contains the single items, something like this:

public class Message {



   String username;

   String useruid;

   String photoURL;

   String message;

   Date timestamp;

   //...getter and setter

}

Even better would be to have a Message object just contain a userId, messageText and timeStamp. that's all you would need.

Then you could pass a List<Message> messages into your adapter.

To sort the message list you can implement the Comparable class where you can then sort the objects in a way you like.

public class Message implements Comparable<Message>{



   String username;

   String useruid;

   String photoURL;

   String message;

   Date timestamp;



   @Override

   public int compareTo(@NonNull Message o) {

       return this.timestamp.compareTo(o.timestamp)

   }

}

If you have added Comparable to your Messageclass, you can use
Collections.sort(messages); to sort the list.

Just have a look at the java comparable, there are various examples. Also check out this stackoverflow answer.

edit: to answer your additional question:

in your case, when you are getting your elements you would do something like:

List<Message> messages = new ArrayList<Message>();



for(DataSnapshot snapshot : dataSnapshot.getChildren()){

     Message message = new Message();

     message.setName(snapshot.child("roomname").getValue().toString());

     …

     //set all your properties and then add that object to the messages list

     messages.add(message);

     }

Collections.sort(messages); // sort the message list

ChatAdapter chatAdapter = new ChatAdapter(getActivity(), messages);

listView.setAdapter(chatAdapter);