一、效果图

倒计时.png

二、思路

算多少秒，秒数取余60，（满足分后剩下的秒数）
算多少分，秒数除60，再取余60 （总分数满足小时后剩下的分数）
算多少时，秒数除60，除60，再取余24 （总小时满足天后剩下的小时）
算多少天，秒数除60，除60，除24 等到的整数就是天数

三、完整代码：

public static void liveDescCountTime(long ms,TextView tvDays, TextView tvHour,TextView tvMinutes,TextView tvSeconds){
    long totalSeconds = ms / 1000;
    long seconds = totalSeconds % 60;
    long minutes = totalSeconds / 60 % 60;
    long hours = totalSeconds / 60 / 60 % 24;
    long days = totalSeconds / 60 / 60 / 24;

    String dayStr = "";
    if (days > 0){
        if (days > 9) {
            dayStr += days + "";
        } else if (days > 0) {
            dayStr += "0" + days + "";
        } else {
            dayStr += "00";
        }
    } else {
        dayStr = "00";
    }
    tvDays.setText(dayStr);

    String hourStr = "";
    if (hours > 0){
        if (hours > 9) {
            hourStr += hours + "";
        } else if (hours > 0) {
            hourStr += "0" + hours + "";
        } else {
            hourStr += "00";
        }
    } else {
        hourStr = "00";
    }
    tvHour.setText(hourStr);

    String minutesStr = "";
    if (minutes > 9) {
        minutesStr += minutes + "";
    } else if (minutes > 0) {
        minutesStr += "0" + minutes + "";
    } else {
        minutesStr += "00";
    }
    tvMinutes.setText(minutesStr);

    String secondStr = "";
    if (seconds > 9) {
        secondStr += seconds;
    } else if (seconds > 0) {
        secondStr += "0" + seconds;
    } else {
        secondStr += "00";
    }
    tvSeconds.setText(secondStr);
}  

开始倒计时

Observable.interval(1,TimeUnit.MILLISECONDS)
                        .take(saveTime)
                        .observeOn(AndroidSchedulers.mainThread())
                        .subscribe(object :Observer<Long>{
                            override fun onComplete() {
                                
                            }

                            override fun onSubscribe(d: Disposable) {
                                countTimeDisposable = d
                            }

                            override fun onNext(aLong: Long) {
                                TimeUtils.liveDescCountTime(Math.abs(aLong - saveTime),tv_8,tv_2,tv_4,tv_6)
                            }

                            override fun onError(e: Throwable) {

                            }

                        })

注：saveTime就是你的毫秒数