iOS之实现倒计时功能

倒计时在发送验证码是常见的功能，怎么实现这个功能。正所谓会者不难，难者不会。在此遍博客来实现一下。具体代码可以参考 倒计时Demo

一、实现思路

倒计时功能的实现：

当触发倒计时的button时，才进行倒计时功能

倒计时完毕时，使button可用即可以再次点击来重新发送

二、具体代码的实现

EDCountdown.h

//
//  EDCountdown.h
//  Countdown
//
//  Created by humor on 15/12/31.
//  Copyright © 2015年 onefiter. All rights reserved.
//

#import <Foundation/Foundation.h>

@class EDCountdown;

@protocol EDCountdownDelegate <NSObject>

/**
*  周期性的通知外界，自创建计时器到当前时间差值
*
*  @param sender     计时器
*  @param timeOffset 自创建计时器到当前时间差值
*/

- (void)notifyCountTimeCallBack:(id)sender withTimeOffset:(NSTimeInterval)timeOffset;

@end

@interface EDCountdown : NSObject

@property(nonatomic, weak  )   id<EDCountdownDelegate> delegate;
@property(nonatomic, assign)   BOOL isOpen;
@property(nonatomic, assign)   NSTimeInterval timeInterval;

- (void)handleCountTimerEvent:(id)sender;

@end

EDCountdown.m

//
//  EDCountdown.m
//  Countdown
//
//  Created by humor on 15/12/31.
//  Copyright © 2015年 onefiter. All rights reserved.
//

#import "EDCountdown.h"

@interface EDCountdown ()

@property (nonatomic, strong) NSTimer *timer;
@property (nonatomic, assign) NSTimeInterval startTime;

@end

@implementation EDCountdown

- (instancetype)init
{
if (self = [super init]) {

_timeInterval = 1;

}

return self;

}

- (void)dealloc
{
self.isOpen = NO;
}

- (void)setIsOpen:(BOOL)isOpen
{

_isOpen = isOpen;

__block dispatch_block_t mainBlock = NULL;

if (_isOpen) {

mainBlock = ^{

if (_timer.isValid) {

[_timer invalidate];

}

_timer = [NSTimer scheduledTimerWithTimeInterval:_timeInterval target:self selector:@selector(handleCountTimerEvent:) userInfo:nil repeats:YES];

_startTime = CFAbsoluteTimeGetCurrent();

};
}

else
{
mainBlock = ^{

if (_timer.isValid) {
[_timer invalidate];
}

_timer = nil;
};

}

if ([NSThread isMainThread]) {
mainBlock();
}
else
{
dispatch_async(dispatch_get_main_queue(), mainBlock);
}

}

- (void)handleCountTimerEvent:(id)sender
{

if ([_delegate respondsToSelector:@selector(notifyCountTimeCallBack:withTimeOffset:)]) {
NSTimeInterval  deltaTime = CFAbsoluteTimeGetCurrent() - _startTime;

[_delegate notifyCountTimeCallBack:self withTimeOffset:deltaTime];
}
}

@end