iOS中一句代码解决倒计时问题

////  ViewController.m//  HWCountdownDemo////  Created by HenryCheng on 16/1/4.//  Copyright © 2016年 www.igancao.com. All rights reserved.//#import "ViewController.h"#import "UIButton+countDown.h"@interface ViewController ()@property (weak, nonatomic) IBOutlet UIButton *countdownBtn;@end@implementation ViewController- (void)viewDidLoad {    [super viewDidLoad];}- (IBAction)countdownBtnClick:(UIButton *)sender {    [_countdownBtn startWithTime:5 title:@"获取验证码" countDownTitle:@"s" mainColor:[UIColor colorWithRed:84/255.0 green:180/255.0 blue:98/255.0 alpha:1.0f] countColor:[UIColor lightGrayColor]];}- (void)didReceiveMemoryWarning {    [super didReceiveMemoryWarning];    // Dispose of any resources that can be recreated.}@end

这里主要的就是xib拉了一个button然后连接了它的属性和方法，我们可以看到就调用了

[_countdownBtn startWithTime:5 title:@"获取验证码" countDownTitle:@"s" mainColor:[UIColor colorWithRed:84/255.0 green:180/255.0 blue:98/255.0 alpha:1.0f] countColor:[UIColor lightGrayColor]];}

这一句代码，就完成了倒计时功能。
这里我写了一个category，里面代码是这样的

////  UIButton+countDown.m//  LiquoriceDoctorProject////  Created by HenryCheng on 15/12/4.//  Copyright © 2015年 iMac. All rights reserved.//#import "UIButton+countDown.h"@implementation UIButton (countDown)- (void)startWithTime:(NSInteger)timeLine title:(NSString *)title countDownTitle:(NSString *)subTitle mainColor:(UIColor *)mColor countColor:(UIColor *)color {    //倒计时时间    __block NSInteger timeOut = timeLine;    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);    dispatch_source_t _timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queue);    //每秒执行一次    dispatch_source_set_timer(_timer, dispatch_walltime(NULL, 0), 1.0 * NSEC_PER_SEC, 0);    dispatch_source_set_event_handler(_timer, ^{        //倒计时结束，关闭        if (timeOut <= 0) {            dispatch_source_cancel(_timer);            dispatch_async(dispatch_get_main_queue(), ^{                self.backgroundColor = mColor;                [self setTitle:title forState:UIControlStateNormal];                self.userInteractionEnabled = YES;            });        } else {            int allTime = (int)timeLine + 1;            int seconds = timeOut % allTime;                 NSString *timeStr = [NSString stringWithFormat:@"%0.2d", seconds];            dispatch_async(dispatch_get_main_queue(), ^{                self.backgroundColor = color;                [self setTitle:[NSString stringWithFormat:@"%@%@",timeStr,subTitle] forState:UIControlStateNormal];                self.userInteractionEnabled = NO;            });            timeOut--;        }    });    dispatch_resume(_timer);}@end

关于这个方法的定义

////  UIButton+countDown.h//  LiquoriceDoctorProject////  Created by HenryCheng on 15/12/4.//  Copyright © 2015年 iMac. All rights reserved.//#import <UIKit/UIKit.h>@interface UIButton (countDown)/** *  倒计时按钮 * *  @param timeLine 倒计时总时间 *  @param title    还没倒计时的title *  @param subTitle 倒计时中的子名字，如时、分 *  @param mColor   还没倒计时的颜色 *  @param color    倒计时中的颜色 */- (void)startWithTime:(NSInteger)timeLine title:(NSString *)title countDownTitle:(NSString *)subTitle mainColor:(UIColor *)mColor countColor:(UIColor *)color;@end

在对应的ViewController.m文件中引入

#import "UIButton+countDown.h"

即可使用。还需要设置对应的按钮类型为Custom避免闪烁。