廢話不多說直接上程式碼

private fun countDown() {
        btn_send_code_activity_login.isEnabled = false
        disPose = Flowable.intervalRange(0,
                120,
                0,
                1,
                TimeUnit.SECONDS)
                .observeOn(AndroidSchedulers.mainThread())
                .doOnNext
 
 {
                    btn_send_code_activity_login
                            .text = String.format(getString(R.string.label_code_time), 120 - it)
                }
                .doOnComplete {
                    btn_send_code_activity_login.isEnabled = true
                    btn_send_code_activity_login.text
 
 = getString(R.string.label_get_code)
                }
                .`as`(AutoDispose.autoDisposable(AndroidLifecycleScopeProvider.from(this)))
                .subscribe()
    }

這裡利用intervalRange引數意思如下

 /**
     * Signals a range of long values, the first after some initial delay and the rest periodically after
 
.
     * <p>
     * The sequence completes immediately after the last value (start + count - 1) has been reached.
     * <dl>
     *  <dt><b>Backpressure:</b></dt>
     *  <dd>The operator signals a {@code MissingBackpressureException} if the downstream can't keep up.</dd>
     *  <dt><b>Scheduler:</b></dt>
     *  <dd>{@code intervalRange} by default operates on the {@link Schedulers#computation() computation} {@link Scheduler}.</dd>
     * </dl>
     * @param start that start value of the range
     * @param count the number of values to emit in total, if zero, the operator emits an onComplete after the initial delay.
     * @param initialDelay the initial delay before signaling the first value (the start)
     * @param period the period between subsequent values
     * @param unit the unit of measure of the initialDelay and period amounts
     * @return the new Flowable instance
     */
    @CheckReturnValue
    @BackpressureSupport(BackpressureKind.ERROR)
    @SchedulerSupport(SchedulerSupport.COMPUTATION)
    public static Flowable<Long> intervalRange(long start, long count, long initialDelay, long period, TimeUnit unit) {
        return intervalRange(start, count, initialDelay, period, unit, Schedulers.computation());
    }