Recyclerview Adapter（Android）中的数据处理位置

Question

我的日期时间当前存储为UNIX时间戳。 我想在Recyclerview中将其显示为h：mm a。

我应该在哪里将UNIX时间戳转换为RecyclerView Adapter / Viewholder中的正常时间（就最佳性能而言）？

我应该在RecyclerView.Adapter的getItemViewType(int position)还是onBindViewHolder或ViewHolder类的bind函数中执行此ViewHolder ？

编辑：我的代码

public class ChatListAdapter extends RecyclerView.Adapter {


    private final LayoutInflater mInflater;
    private List<Chat> mChats;
    private final String ownerMe = "OWNER_ME";
    private static final int VIEW_TYPE_MESSAGE_ME = 1;
    private static final int VIEW_TYPE_MESSAGE_ME_CORNER = 2;
    private static final int VIEW_TYPE_MESSAGE_BF = 3;
    private static final int VIEW_TYPE_MESSAGE_BF_CORNER = 4;

    ChatListAdapter(Context context) {mInflater = LayoutInflater.from(context);}

    @Override
    public int getItemViewType(int position) {
        Chat chat = mChats.get(position);

        if(chat.getUser().equals(ownerMe)) {
            if(position == mChats.size()-1) {
                return VIEW_TYPE_MESSAGE_ME_CORNER;
            }
            if(chat.getUser().equals(mChats.get(position+1).getUser())) {
                return VIEW_TYPE_MESSAGE_ME;
            } else {
                return VIEW_TYPE_MESSAGE_ME_CORNER;
            }
        } else {
            if(position == mChats.size()-1) {
                return VIEW_TYPE_MESSAGE_BF_CORNER;
            }
            if(chat.getUser().equals(mChats.get(position+1).getUser())) {
                return VIEW_TYPE_MESSAGE_BF;
            } else {
                return VIEW_TYPE_MESSAGE_BF_CORNER;
            }
        }
    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view;

        if(viewType == VIEW_TYPE_MESSAGE_ME || viewType == VIEW_TYPE_MESSAGE_ME_CORNER) {
            view = mInflater.inflate(R.layout.recyclerview_item_right, parent, false);
            return new MeMessageHolder(view);
        } else if (viewType == VIEW_TYPE_MESSAGE_BF || viewType == VIEW_TYPE_MESSAGE_BF_CORNER) {
            view = mInflater.inflate(R.layout.recyclerview_item_left, parent, false);
            return new BfMessageHolder(view);
        }
        return null;

    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
        if (mChats != null) {
            Chat current = mChats.get(position);
            long unixTime= current.getUnixTime();
            Date time = new java.util.Date(unixTime*1000L);
            SimpleDateFormat sdf = new java.text.SimpleDateFormat("h:mm a");
            String formattedTime = sdf.format(time);

            switch (holder.getItemViewType()) {
                case VIEW_TYPE_MESSAGE_ME:
                    ((MeMessageHolder) holder).bind(current, formattedTime, false);
                    break;
                case VIEW_TYPE_MESSAGE_ME_CORNER:
                    ((MeMessageHolder) holder).bind(current, formattedTime, true);
                    break;
                case VIEW_TYPE_MESSAGE_BF:
                    ((BfMessageHolder) holder).bind(current, formattedTime, false);
                    break;
                case VIEW_TYPE_MESSAGE_BF_CORNER:
                    ((BfMessageHolder) holder).bind(current, formattedTime, true);
                    break;
            }
        }
    }

    class MeMessageHolder extends RecyclerView.ViewHolder {
        private final TextView chatItemView;
        private final ImageView cornerRightIImageView;
        private final ConstraintLayout constraintLayout;
        private final TextView timeItemView;


        private MeMessageHolder(View itemView) {
            super(itemView);
            chatItemView = itemView.findViewById(R.id.textView);
            cornerRightIImageView = itemView.findViewById(R.id.corner_view_right);
            constraintLayout = itemView.findViewById(R.id.chat_bubble_id);
            timeItemView = itemView.findViewById(R.id.text_message_time);

        }

        void bind(Chat chat, String formattedTime, boolean isCorner) {
            chatItemView.setText(chat.getMessage());
            timeItemView.setText(formattedTime);
            if(isCorner) {
                constraintLayout.setBackgroundResource(R.drawable.chat_bubble_v2);
            } else {
                cornerRightIImageView.setVisibility(View.INVISIBLE);
            }
        }
    }

    class BfMessageHolder extends RecyclerView.ViewHolder {
        private final TextView chatItemView;
        private final ImageView cornerLeftImageView;
        private final ConstraintLayout constraintLayout;
        private final TextView timeItemView;

        private BfMessageHolder(View itemView) {
            super(itemView);
            chatItemView = itemView.findViewById(R.id.textView);
            cornerLeftImageView = itemView.findViewById(R.id.corner_view_left);
            constraintLayout = itemView.findViewById(R.id.chat_bubble_id);
            timeItemView = itemView.findViewById(R.id.text_message_time);
        }

        void bind(Chat chat, String formattedTime, boolean isCorner) {
            chatItemView.setText(chat.getMessage());
            timeItemView.setText(formattedTime);
            if(isCorner) {
                constraintLayout.setBackgroundResource(R.drawable.chat_bubble_v3);
            } else {
                cornerLeftImageView.setVisibility(View.INVISIBLE);
            }
        }
    }

    void setChats(List<Chat> chats) {
        mChats = chats;
        notifyDataSetChanged();
    }

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

这是方法正确吗？ 我在onBindViewHolder方法中格式化了日期

Answer 1

这取决于您是要在recyclerview的不同项目上显示不同的日期，还是要在recyclerview的所有项目上显示相同的日期。 如果要对所有项目显示相同的日期，最好在适配器之外进行，然后将解析的日期传递给recyclerview适配器。 或者，如果要在每个项目上显示不同的日期，则应在onBindViewHolder中执行此操作，因为它可以访问项目位置。

请记住，getItemViewType用于从可用视图类型中获取视图类型。 如果要放大多个视图，则使用此方法。 考虑一个chatapp，其中view1将在左侧显示消息，而view2将在右侧显示消息； 全部都在同一recyclerview中。

onBindViewHolder方法仅执行通用绑定任务。 绑定内容：展开视图的项目和数据。

Answer 2

似乎是业务逻辑。 因此，例如，我建议您在Model中将UNIX时间戳转换。

class Chat {

   private Long unixTime;

   // another code

   public Long getUnixTime() {
      return unixTime;
   }

   public String convertedUnixTimeToString(String format) {
      // Also need to add some format validation     
      if(format == null) {
         // do some action, like trowing exception, or setting default value in format
      } 

      Date time = new java.util.Date(unixTime*1000L);
      SimpleDateFormat sdf = new java.text.SimpleDateFormat(format);

      return sdf.format(time);
   }

}

我建议您使用JodaTime进行日期和时间格式设置。 非常有用的东西。

然后，只需修改您的代码

public class ChatListAdapter extends RecyclerView.Adapter {


    private final LayoutInflater mInflater;
    private List<Chat> mChats;
    private final String ownerMe = "OWNER_ME";
    private static final int VIEW_TYPE_MESSAGE_ME = 1;
    private static final int VIEW_TYPE_MESSAGE_ME_CORNER = 2;
    private static final int VIEW_TYPE_MESSAGE_BF = 3;
    private static final int VIEW_TYPE_MESSAGE_BF_CORNER = 4;

    ChatListAdapter(Context context) {mInflater = LayoutInflater.from(context);}

    @Override
    public int getItemViewType(int position) {
        Chat chat = mChats.get(position);

        if(chat.getUser().equals(ownerMe)) {
            if(position == mChats.size()-1) {
                return VIEW_TYPE_MESSAGE_ME_CORNER;
            }
            if(chat.getUser().equals(mChats.get(position+1).getUser())) {
                return VIEW_TYPE_MESSAGE_ME;
            } else {
                return VIEW_TYPE_MESSAGE_ME_CORNER;
            }
        } else {
            if(position == mChats.size()-1) {
                return VIEW_TYPE_MESSAGE_BF_CORNER;
            }
            if(chat.getUser().equals(mChats.get(position+1).getUser())) {
                return VIEW_TYPE_MESSAGE_BF;
            } else {
                return VIEW_TYPE_MESSAGE_BF_CORNER;
            }
        }
    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view;

        if(viewType == VIEW_TYPE_MESSAGE_ME || viewType == VIEW_TYPE_MESSAGE_ME_CORNER) {
            view = mInflater.inflate(R.layout.recyclerview_item_right, parent, false);
            return new MeMessageHolder(view);
        } else if (viewType == VIEW_TYPE_MESSAGE_BF || viewType == VIEW_TYPE_MESSAGE_BF_CORNER) {
            view = mInflater.inflate(R.layout.recyclerview_item_left, parent, false);
            return new BfMessageHolder(view);
        }
        return null;

    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
        if (mChats != null) {
            Chat current = mChats.get(position);

            switch (holder.getItemViewType()) {
                case VIEW_TYPE_MESSAGE_ME:
                    ((MeMessageHolder) holder).bind(current, false);
                    break;
                case VIEW_TYPE_MESSAGE_ME_CORNER:
                    ((MeMessageHolder) holder).bind(current, true);
                    break;
                case VIEW_TYPE_MESSAGE_BF:
                    ((BfMessageHolder) holder).bind(current, false);
                    break;
                case VIEW_TYPE_MESSAGE_BF_CORNER:
                    ((BfMessageHolder) holder).bind(current, true);
                    break;
            }
        }
    }

    class MeMessageHolder extends RecyclerView.ViewHolder {
        private final TextView chatItemView;
        private final ImageView cornerRightIImageView;
        private final ConstraintLayout constraintLayout;
        private final TextView timeItemView;


        private MeMessageHolder(View itemView) {
            super(itemView);
            chatItemView = itemView.findViewById(R.id.textView);
            cornerRightIImageView = itemView.findViewById(R.id.corner_view_right);
            constraintLayout = itemView.findViewById(R.id.chat_bubble_id);
            timeItemView = itemView.findViewById(R.id.text_message_time);

        }

        void bind(Chat chat, boolean isCorner) {
            chatItemView.setText(chat.getMessage());
            timeItemView.setText(chat.convertedUnixTimeToString("h:mm a"));
            if(isCorner) {
                constraintLayout.setBackgroundResource(R.drawable.chat_bubble_v2);
            } else {
                cornerRightIImageView.setVisibility(View.INVISIBLE);
            }
        }
    }

    class BfMessageHolder extends RecyclerView.ViewHolder {
        private final TextView chatItemView;
        private final ImageView cornerLeftImageView;
        private final ConstraintLayout constraintLayout;
        private final TextView timeItemView;

        private BfMessageHolder(View itemView) {
            super(itemView);
            chatItemView = itemView.findViewById(R.id.textView);
            cornerLeftImageView = itemView.findViewById(R.id.corner_view_left);
            constraintLayout = itemView.findViewById(R.id.chat_bubble_id);
            timeItemView = itemView.findViewById(R.id.text_message_time);
        }

        void bind(Chat chat, boolean isCorner) {
            chatItemView.setText(chat.getMessage());
            timeItemView.setText(chat.convertedUnixTimeToString("h:mm a"));
            if(isCorner) {
                constraintLayout.setBackgroundResource(R.drawable.chat_bubble_v3);
            } else {
                cornerLeftImageView.setVisibility(View.INVISIBLE);
            }
        }
    }

    void setChats(List<Chat> chats) {
        mChats = chats;
        notifyDataSetChanged();
    }

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

Answer 3

您需要通过将时间戳乘以1000来将其转换为毫秒：

java.util.Date dateTime=new java.util.Date((long)timeStamp*1000);

然后首先您需要将UNIX时间戳转换为日期时间格式

final long unixTime = 1372339860;
final String formattedDtm = Instant.ofEpochSecond(unixTime)
        .atZone(ZoneId.of("GMT-4"))
        .format(formatter);

System.out.println(formattedDtm);   // => '2013-06-27 09:31:00'

那么您想将此数据存储到RecyclerView的字段值，然后可以从这种时间格式像h:mm格式化

Answer 4

您应该在onBindViewHolder方法中更新UI更改。 您可以在onBindViewHolder调用ViewHolder bind方法。

例：

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

  @NonNull
  @Override
  public ViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
    View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.sample_view, viewGroup, false);
    return new ViewHolder(view);
  }

  @Override
  public void onBindViewHolder(@NonNull ViewHolder viewHolder, int i) {
    viewHolder.bind(i);
  }

  public class ViewHolder extends RecyclerView.ViewHolder {

    public ViewHolder(@NonNull View itemView) {
      super(itemView);
    }

    void bind(int position) {
      // Do your data updates here.
    }
  }
}

Answer 5

只需将SimpleDateFormat与yyyy-MM-dd模式一起使用即可。

在RecyclerView. onBindViewHolder方法中应用SimpleDateFormat.format(millis) RecyclerView.