前言
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
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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);
}
}
}
}
}
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总结
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