我想用Firebase编写一个ChatApp程序。现在我正在显示我聊天的用户。但现在我希望它们按我使用的日期字符串排序： 例如：21-06-2017 17:20。它应该从最新的时间到最早的时间排序。
我的适配器：
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;
}
这就是我获取ArrayLists的方式：
`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);`
但是如何将其作为List传递？ 如何将它们添加到列表中？
甚至可以对它进行排序吗？
我希望你们能帮帮我:) 感谢。
答案 0 :(得分：1)
这当然是可能的。 但首先，您的数据结构看起来很怪异且不实用。
您的消息以单个数组传递，这使得它非常复杂：
ArrayList<String> username, ArrayList<String> useruid, ArrayList<String> photoURL, ArrayList<String> lastmessage, ArrayList<String> lastmessagetime
最好有一个Message对象列表，其中一个消息对象包含单个项目，如下所示：
public class Message {
String username;
String useruid;
String photoURL;
String message;
Date timestamp;
//...getter and setter
}
更好的是让Message对象只包含userId，messageText和timeStamp。这就是你所需要的一切。
然后你可以将List<Message> messages传递给适配器。
要对消息列表进行排序，您可以实现Comparable类，然后您可以按照自己喜欢的方式对对象进行排序。
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)
}
}
如果您已将Comparable添加到Message课程，则可以使用
Collections.sort(messages);对列表进行排序。
只需查看java comparable，即various examples。另请查看此stackoverflow answer.
编辑：回答您的其他问题：
在您的情况下，当您获得元素时，您会执行以下操作：
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);