Android利用RecyclerView实现列表倒计时效果

最近面试时，面试官问了一个列表倒计时效果如何实现，然后脑袋突然懵的了o(∩_∩)o，现在记录一下。

运行效果图

实现思路

实现方法主要有两个：
1.为每个开始倒计时的item启动一个定时器，再做更新item处理；
2.只启动一个定时器，然后遍历数据，再做再做更新item处理。
经过思考，包括性能、实现等方面，决定使用第2种方式实现。

实现过程

• 数据实体

/** 
  * 总共的倒计时的时间(结束时间-开始时间),单位：毫秒 
  * 例: 2019-02-23 11:00:30 与 2019-02-23 11:00:00 之间的相差的毫秒数 
  */  
 private long totaltime;  
 /** 
  * 倒计时是否在暂停状态 
  */  
 private boolean ispause = true;  

• 倒计时
  timer

mtimer.schedule(mtask, 0, 1000);

timertask

 class mytask extends timertask {
        @override
        public void run() {
            if (mlist.isempty()) {
                return;
            }
            int size = mlist.size();
            countdowntimerbean bean;
            long totaltime;
            for (int i = 0; i < size; i++) {
                bean = mlist.get(i);
                if (!bean.ispause()) {//不处于暂停状态
                    totaltime = bean.gettotaltime() - 1000;
                    if (totaltime <= 0) {
                        bean.setpause(true);
                        bean.settotaltime(0);
                    }
                    bean.settotaltime(totaltime);
                    message message = mhandler.obtainmessage(1);
                    message.arg1 = i;
                    mhandler.sendmessage(message);
                }
            }
        }
    }

• 线程交互更新item

 mhandler = new handler(looper.getmainlooper()) {
            @override
            public void handlemessage(message msg) {
                switch (msg.what) {
                    case 1:
                        notifyitemchanged(msg.arg1, "update-time");
                        break;
                }
            }
        };

• 性能优化方面
  1.调用notifyitemchanged()方法后，不要更新整个item(比如说item包含图片，不需要变的)，所以要重写onbindviewholder( holder , int , list

@override
    public void onbindviewholder(@nonnull holder holder, int position, @nonnull list<object> payloads) {
        if (payloads.isempty()) {
            onbindviewholder(holder, position);
            return;
        }
        //更新某个控件,比如说只需要更新时间信息，其他不用动
        countdowntimerbean bean = mlist.get(position);
        long day = bean.gettotaltime() / (1000 * 60 * 60 * 24);
        long hour = (bean.gettotaltime() / (1000 * 60 * 60) - day * 24);
        long min = ((bean.gettotaltime() / (60 * 1000)) - day * 24 * 60 - hour * 60);
        long s = (bean.gettotaltime() / 1000 - day * 24 * 60 * 60 - hour * 60 * 60 - min * 60);
        holder.tvtime.settext("剩余时间: " + day + "天" + hour + "小时" + min + "分" + s + "秒");
        holder.btnaction.settext(bean.ispause() ? "开始" : "暂停");
        holder.btnaction.setenabled(bean.gettotaltime() != 0);
    }

2.销毁资源操作：

   /**
     * 销毁资源
     */
    public void destroy() {
        mhandler.removemessages(1);
        if (mtimer != null) {
            mtimer.cancel();
            mtimer.purge();
            mtimer = null;
        }
    }

• recyclerview.adapter部分源码

public class countdowntimeradapter extends recyclerview.adapter<countdowntimeradapter.holder> {
    private static final string tag = "countdowntimeradapter->";
    private list<countdowntimerbean> mlist;//数据
    private handler mhandler;//线程调度，用来更新列表

    private timer mtimer;
    private mytask mtask;

    public countdowntimeradapter() {
        mlist = new arraylist<>();
        mhandler = new handler(looper.getmainlooper()) {
            @override
            public void handlemessage(message msg) {
                switch (msg.what) {
                    case 1:
                        notifyitemchanged(msg.arg1, "update-time");
                        break;
                }
            }
        };
        mtask = new mytask();
    }

    public void bindadaptertorecyclerview(@nonnull recyclerview view) {
        view.setadapter(this);
    }

    /**
     * 设置新的数据源
     *
     * @param list 数据
     */
    public void setnewdata(@nonnull list<countdowntimerbean> list) {
        destroy();
        mlist.clear();
        mlist.addall(list);
        notifydatasetchanged();
        if (mtimer == null) {
            mtimer = new timer();
        }
        mtimer.schedule(mtask, 0, 1000);
    }

    /**
     * 销毁资源
     */
    public void destroy() {
        mhandler.removemessages(1);
        if (mtimer != null) {
            mtimer.cancel();
            mtimer.purge();
            mtimer = null;
        }
    }

    @nonnull
    @override
    public holder oncreateviewholder(@nonnull viewgroup viewgroup, int i) {
        view view = layoutinflater.from(viewgroup.getcontext()).inflate(r.layout.item_count_down_timer, viewgroup, false);
        return new holder(view);
    }

    @override
    public void onbindviewholder(@nonnull holder holder, int position, @nonnull list<object> payloads) {
        if (payloads.isempty()) {
            onbindviewholder(holder, position);
            return;
        }
        //更新某个控件,比如说只需要更新时间信息，其他不用动
        countdowntimerbean bean = mlist.get(position);
        long day = bean.gettotaltime() / (1000 * 60 * 60 * 24);
        long hour = (bean.gettotaltime() / (1000 * 60 * 60) - day * 24);
        long min = ((bean.gettotaltime() / (60 * 1000)) - day * 24 * 60 - hour * 60);
        long s = (bean.gettotaltime() / 1000 - day * 24 * 60 * 60 - hour * 60 * 60 - min * 60);
        holder.tvtime.settext("剩余时间: " + day + "天" + hour + "小时" + min + "分" + s + "秒");
        holder.btnaction.settext(bean.ispause() ? "开始" : "暂停");
        holder.btnaction.setenabled(bean.gettotaltime() != 0);
    }

    @override
    public void onbindviewholder(@nonnull final holder holder, int position) {
        holder.ivicon.setimageresource(r.mipmap.ic_launcher_round);
        final countdowntimerbean bean = mlist.get(position);
        long day = bean.gettotaltime() / (1000 * 60 * 60 * 24);
        long hour = (bean.gettotaltime() / (1000 * 60 * 60) - day * 24);
        long min = ((bean.gettotaltime() / (60 * 1000)) - day * 24 * 60 - hour * 60);
        long s = (bean.gettotaltime() / 1000 - day * 24 * 60 * 60 - hour * 60 * 60 - min * 60);
        holder.tvtime.settext("剩余时间: " + day + "天" + hour + "小时" + min + "分" + s + "秒");
        holder.btnaction.settext(bean.ispause() ? "开始" : "暂停");
        holder.btnaction.setenabled(bean.gettotaltime() != 0);
        holder.btnaction.setonclicklistener(new view.onclicklistener() {
            @override
            public void onclick(view v) {
                if (bean.ispause()) {
                    bean.setpause(false);
                    holder.btnaction.settext("暂停");
                } else {
                    bean.setpause(true);
                    holder.btnaction.settext("开始");
                }
            }
        });
    }

    @override
    public int getitemcount() {
        return mlist.size();
    }

    class holder extends recyclerview.viewholder {
        private imageview ivicon;
        private textview tvtime;
        private button btnaction;

        holder(@nonnull view itemview) {
            super(itemview);
            ivicon = itemview.findviewbyid(r.id.iv_icon);
            tvtime = itemview.findviewbyid(r.id.tv_time);
            btnaction = itemview.findviewbyid(r.id.btn_action);
        }
    }

    class mytask extends timertask {
        @override
        public void run() {
            if (mlist.isempty()) {
                return;
            }
            int size = mlist.size();
            countdowntimerbean bean;
            long totaltime;
            for (int i = 0; i < size; i++) {
                bean = mlist.get(i);
                if (!bean.ispause()) {//不处于暂停状态
                    totaltime = bean.gettotaltime() - 1000;
                    if (totaltime <= 0) {
                        bean.setpause(true);
                        bean.settotaltime(0);
                    }
                    bean.settotaltime(totaltime);
                    message message = mhandler.obtainmessage(1);
                    message.arg1 = i;
                    mhandler.sendmessage(message);
                }
            }
        }
    }
}

项目地址

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如有问题，欢迎及时沟通。