如何recyclerview或列表視圖

Question

如何顯示日期或今天，昨天像文本

談話之間例如WhatsApp

Answer 1

你需要創建一個新的ViewHolder顯示日期在談話間爲此目的

例如：

// Different types of rows 
private static final int TYPE_ITEM_LEFT = 0; 
private static final int TYPE_ITEM_RIGHT = 1; 
private static final int TYPE_ITEM_DATE_CONTAINER = 2; 

public class MyAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> { 
class ViewHolder0 extends RecyclerView.ViewHolder { 
    // Viewholder for row type 0 
} 

class ViewHolder1 extends RecyclerView.ViewHolder { 
    // Viewholder for row type 1 
} 

class ViewHolder2 extends RecyclerView.ViewHolder { 
    // Viewholder for row type 2 
} 

@Override 
public void onBindViewHolder(final RecyclerView.ViewHolder viewHolder, int position) { 
    if (viewHolder.getItemViewType() == TYPE_ITEM_LEFT) { 
     // Code to populate type 0 view here 
    } else if (viewHolder.getItemViewType() == TYPE_ITEM_RIGHT) { 
     // code to populate type 1 view here 
    } esle if (viewHolder.getItemViewType() == TYPE_ITEM_DATE_CONTAINER) { 
     // code to populate type 2 view here 
    } 
} 

Answer 2

MainActivity

public class MainActivity extends AppCompatActivity { 

    private ChatAdapter chatAdapter; 
    private RecyclerView recyclerView; 
    private Context context; 
    private int loggedInUserID; 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     bindRecyclerView(); 
     // TODO get logged in user id and initialize into 'loggedInUserID' 
    } 

    @Override 
    protected void onResume() { 
     super.onResume(); 
     getData(); 
    } 

    private void getData() { 
     /** 
     *Your server call to get data and parse json to your appropriate model 
     * after parsing json to model simply call the 
     */ 
     List<ChatModel> chatModelList = ParseData.chatParser(jsonArray); 
     groupDataIntoHashMap(chatModelList); 
    } 

    private void bindRecyclerView() { 
     chatAdapter = new ChatAdapter(null); 
     chatAdapter.setUser(loggedInUserID); 
     RecyclerView.LayoutManager mLayoutManager = new LinearLayoutManager(context); 
     recyclerView.setLayoutManager(mLayoutManager); 
     recyclerView.setItemAnimator(new DefaultItemAnimator()); 
     recyclerView.setAdapter(chatAdapter); 
    } 


    private void groupDataIntoHashMap(List<ChatModel> chatModelList) { 
     LinkedHashMap<String, Set<ChatModel>> groupedHashMap = new LinkedHashMap<>(); 
     Set<ChatModel> list = null; 
     for (ChatModel chatModel : chatModelList) { 
      //Log.d(TAG, travelActivityDTO.toString()); 
      String hashMapKey = DateParser.convertDateToString(chatModel.getChatTime()); 
      //Log.d(TAG, "start date: " + DateParser.convertDateToString(travelActivityDTO.getStartDate())); 
      if (groupedHashMap.containsKey(hashMapKey)) { 
       // The key is already in the HashMap; add the pojo object 
       // against the existing key. 
       groupedHashMap.get(hashMapKey).add(chatModel); 
      } else { 
       // The key is not there in the HashMap; create a new key-value pair 
       list = new LinkedHashSet<>(); 
       list.add(chatModel); 
       groupedHashMap.put(hashMapKey, list); 
      } 
     } 
     //Generate list from map 
     generateListFromMap(groupedHashMap); 

    } 


    private List<ListObject> generateListFromMap(LinkedHashMap<String, Set<ChatModel>> groupedHashMap) { 
     // We linearly add every item into the consolidatedList. 
     List<ListObject> consolidatedList = new ArrayList<>(); 
     for (String date : groupedHashMap.keySet()) { 
      DateObject dateItem = new DateObject(); 
      dateItem.setDate(date); 
      consolidatedList.add(dateItem); 
      for (ChatModel chatModel : groupedHashMap.get(date)) { 
       ChatModelObject generalItem = new ChatModelObject(); 
       generalItem.setChatModel(chatModel); 
       consolidatedList.add(generalItem); 
      } 
     } 

     chatAdapter.setDataChange(consolidatedList); 

     return consolidatedList; 
    } 

} 

ChatModel.java

public class ChatModel implements Serializable { 
     private String messageId; 
     private int userId; 
     private String firstName; 
     private String userName; 
     private String message; 
     private Date chatTime; 

     //TODO generate getter and setter 

    } 

ListObject.java（至determind消息的類型）

public abstract class ListObject { 
     public static final int TYPE_DATE = 0; 
     public static final int TYPE_GENERAL_RIGHT = 1; 
     public static final int TYPE_GENERAL_LEFT = 2; 

     abstract public int getType(int userId); 
    } 

DateObject.java

public class DateObject extends ListObject { 
     private String date; 

     public String getDate() { 
      return date; 
     } 

     public void setDate(String date) { 
      this.date = date; 
     } 

     @Override 
     public int getType(int userId) { 
      return TYPE_DATE; 
     } 
    } 

ChatModelObject.java

public class ChatModelObject extends ListObject { 

     private ChatModel chatModel; 

     public ChatModel getChatModel() { 
      return chatModel; 
     } 

     public void setChatModel(ChatModel chatModel) { 
      this.chatModel = chatModel; 
     } 

     @Override 
     public int getType(int userId) { 
      if (this.chatModel.getUserId() == userId) { 
       return TYPE_GENERAL_RIGHT; 
      } else 
       return TYPE_GENERAL_LEFT; 
     } 
    } 

DateParse.java解析日期分組聊天

public class DateParser { 
     private static DateFormat dateFormat1 = new SimpleDateFormat("dd/MM/yyyy"); 

     public static String convertDateToString(Date date) { 
      String strDate = ""; 
      strDate = dateFormat1.format(date); 
      return strDate; 
     } 
    } 

ChatAdapter.java

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

     private List<ListObject> listObjects; 
     private int loggedInUserId; 

     public ChatAdapter(List<ListObject> listObjects) { 
      this.listObjects = listObjects; 
     } 

     public void setUser(int userId) { 
      this.loggedInUserId = userId; 
     } 

     public void setDataChange(List<ListObject> asList) { 
      this.listObjects = asList; 
      //now, tell the adapter about the update 
      notifyDataSetChanged(); 
     } 

     @Override 
     public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { 
      RecyclerView.ViewHolder viewHolder = null; 
      LayoutInflater inflater = LayoutInflater.from(parent.getContext()); 
      switch (viewType) { 
       case ListObject.TYPE_GENERAL_RIGHT: 
        View currentUserView = LayoutInflater.from(parent.getContext()).inflate(R.layout.recyclerview_chat_list_row_right, parent, false); 
        viewHolder = new ChatRightViewHolder(currentUserView); // view holder for normal items 
        break; 
       case ListObject.TYPE_GENERAL_LEFT: 
        View otherUserView = LayoutInflater.from(parent.getContext()).inflate(R.layout.recyclerview_chat_list_row_left, parent, false); 
        viewHolder = new ChatLeftViewHolder(otherUserView); // view holder for normal items 
        break; 
       case ListObject.TYPE_DATE: 
        View v2 = inflater.inflate(R.layout.date_row, parent, false); 
        viewHolder = new DateViewHolder(v2); 
        break; 
      } 

      return viewHolder; 

     } 

     @Override 
     public void onBindViewHolder(RecyclerView.ViewHolder viewHolder, int position) { 
      switch (viewHolder.getItemViewType()) { 
       case ListObject.TYPE_GENERAL_RIGHT: 
        ChatModelObject generalItem = (ChatModelObject) listObjects.get(position); 
        ChatRightViewHolder chatViewHolder = (ChatRightViewHolder) viewHolder; 
        chatViewHolder.bind(generalItem.getChatModel()); 
        break; 
       case ListObject.TYPE_GENERAL_LEFT: 
        ChatModelObject generalItemLeft = (ChatModelObject) listObjects.get(position); 
        ChatLeftViewHolder chatLeftViewHolder = (ChatLeftViewHolder) viewHolder; 
        chatLeftViewHolder.bind(generalItemLeft.getChatModel()); 
        break; 
       case ListObject.TYPE_DATE: 
        DateObject dateItem = (DateObject) listObjects.get(position); 
        DateViewHolder dateViewHolder = (DateViewHolder) viewHolder; 
        dateViewHolder.bind(dateItem.getDate()); 
        break; 
      } 
     } 

     @Override 
     public int getItemCount() { 
      if (listObjects != null) { 
       return listObjects.size(); 
      } 
      return 0; 
     } 

     @Override 
     public int getItemViewType(int position) { 
      return listObjects.get(position).getType(loggedInUserId); 
     } 

     public ListObject getItem(int position) { 
      return listObjects.get(position); 
     } 
    } 

ChatRightViewHolder.java爲當前用戶消息

public class ChatRightViewHolder extends RecyclerView.ViewHolder { 
     private final String TAG = ChatRightViewHolder.class.getSimpleName(); 

     public ChatRightViewHolder(View itemView) { 
      super(itemView); 
      //TODO initialize your xml views 
     } 

     public void bind(final ChatModel chatModel) { 
      //TODO set data to xml view via textivew.setText(); 
     } 
    } 

ChatLeftViewHolder.java用於顯示其他用戶消息。

public class ChatLeftViewHolder extends RecyclerView.ViewHolder { 
     private final String TAG = ChatRightViewHolder.class.getSimpleName(); 

     public ChatLeftViewHolder(View itemView) { 
      super(itemView); 
      //TODO initialize your xml views 
     } 

     public void bind(final ChatModel chatModel) { 
      //TODO set data to xml view via textivew.setText(); 
     } 
    } 

DateViewHolder.java顯示日期

public class DateViewHolder extends RecyclerView.ViewHolder { 
     public DateViewHolder(View itemView) { 
      super(itemView); 
      //TODO initialize your xml views 
     } 

     public void bind(final String date) { 
      //TODO set data to xml view via textivew.setText(); 
     } 
    }