如何在Android中比较两个日期

Question

我在android studio中使用firebase创建了一个聊天应用程序，我的所有活动都正常运行，除了日期显示，

我想设置日期在一次如果它是相同的否则显示新的日期如果它是不相同的上一个日期我试图设置但它显示一些错误

Process: com.example.registration, PID: 13007
    java.lang.ArrayIndexOutOfBoundsException: length=10; index=-1
        at java.util.ArrayList.get(ArrayList.java:439)
        at com.example.registration.myadapter.onBindViewHolder(myadapter.java:49)
        at com.example.registration.myadapter.onBindViewHolder(myadapter.java:19)
        at androidx.recyclerview.widget.RecyclerView$Adapter.onBindViewHolder(RecyclerView.java:7065)
        at androidx.recyclerview.widget.RecyclerView$Adapter.bindViewHolder(RecyclerView.java:7107)
        at androidx.recyclerview.widget.RecyclerView$Recycler.tryBindViewHolderByDeadline(RecyclerView.java:6012)
        at androidx.recyclerview.widget.RecyclerView$Recycler.tryGetViewHolderForPositionByDeadline(RecyclerView.java:6279)
        at androidx.recyclerview.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:6118)
        at androidx.recyclerview.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:6114)
        at androidx.recyclerview.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:2303)
       

这里是错误

我获取当前日期

SimpleDateFormat sdf = new SimpleDateFormat("dd-MM-yyyy");
String currentDate = sdf.format(new Date());

然后把它交给聊天室。java使用按钮。OnclickListner

 sendmsg.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String textmsg=inputmsg.getText().toString();
                if(!textmsg.equals("")){
                    sendmessage(firebaseUser.getUid(),userref,textmsg,currentDate,currenttime);

                }
                else{
                    Toast.makeText(chatscreen.this, "ENTER SOMETHING TO SEND MESSAGE", Toast.LENGTH_SHORT).show();
                }
                inputmsg.setText("");
            }
        });

这是我的适配器

    @Override
    public void onBindViewHolder(@NonNull @NotNull myadapter.ViewHolder holder, int position) {
        Chat name=values.get(position);
        Chat pname=values.get(position - 1);//line 49
        holder.txtmsg.setText(name.getMessage());
//        holder.date.setText(name.getDate());
        if(!name.getDate().equals(pname.getDate())) {
            holder.time.setText(name.getTime());
        }
        else{
            holder.date.setVisibility(View.INVISIBLE);
        }
        if(position==values.size()-1){
            if(name.getIsseen()){
                holder.textseen.setText("SEEN");
            }
            else{
                holder.textseen.setText("DELIVERED");
            }
        }

    }
    @Override
    public int getItemCount() {
        return values.size();
    }
    public static class ViewHolder extends RecyclerView.ViewHolder {
        public TextView txtmsg;
        public TextView date;
        public TextView time;
        public TextView textseen;
        public View log;
        public ViewHolder(@NonNull @NotNull View itemView) {
            super(itemView);
            txtmsg=(TextView) itemView.findViewById(R.id.usermsg);
            date=(TextView) itemView.findViewById(R.id.date);
            time=(TextView) itemView.findViewById(R.id.time);
            textseen=(TextView) itemView.findViewById(R.id.isseen);

        }
    }

有人知道怎么解决这个问题吗？

Answer 1

对于RecyclerView中的第一项，position将是0，这使得position-1=-1成为无效索引，因此在onBindViewHolder中检查position

@Override
public void onBindViewHolder(@NonNull @NotNull myadapter.ViewHolder holder, int position) {
    Chat name=values.get(position);
    holder.txtmsg.setText(name.getMessage());  
    if(position > 0)
         Chat pname=values.get(position - 1);
         if(!name.getDate().equals(pname.getDate())) {
              holder.time.setText(name.getTime());
         }else{
              holder.date.setVisibility(View.INVISIBLE);
         }
     }  
     if(position==values.size()-1){
        if(name.getIsseen()){
            holder.textseen.setText("SEEN");
        }else{
            holder.textseen.setText("DELIVERED");
        }
     }
}