前言:最近在做一个项目中有一个邮箱认证的功能,发送短信后,60秒后才能重新再次点击认证,如果在倒计时的过程中,退出了当前页面,过一会再返回来看的时候,需要知道之前的倒计时有没有结束,后来想了想,应该用单例可以解决,于是就动手做了一个demo.
image.png
点击进入下一个需要倒计时的页面
image.png
点击开始倒计时
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然后再倒计时到6秒的时候,点back返回,默念3秒钟再进来当前页面,查看倒计时效果
image.png
大概就是这么个效果了,over
下面贴一下代码,时间紧凑,随便写的两个页面,勿见怪哈...
#import <Foundation/Foundation.h>
typedef NS_ENUM(NSInteger, wherefrom){
from1 = 1,
from2 = 2,
from3 = 3,
};
NS_ASSUME_NONNULL_BEGIN
@interface BMWNSTimer : NSObject
{
dispatch_source_t _timer;
}
@property (nonatomic,assign)__block int timeLeft;
@property (nonatomic,assign) wherefrom from; //用于区别哪个倒计时
+ (id)sharedTimerManager;
- (void)countDown;
@end
NS_ASSUME_NONNULL_END
#import "BMWNSTimer.h"
@implementation BMWNSTimer
+ (id)sharedTimerManager{
static BMWNSTimer *manager =nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
if (manager ==nil) {
manager = [[self alloc] init];
}
});
return manager;
}
- (void)countDown{
if (_timeLeft >0) {
if (_timer) {
dispatch_source_cancel(_timer);
}
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT,0);
_timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER,0, 0,queue);
dispatch_source_set_timer(_timer,dispatch_walltime(NULL,0),1.0*NSEC_PER_SEC,0); //每秒执行
dispatch_source_set_event_handler(_timer, ^{
if(_timeLeft<=0){//倒计时结束，关闭
dispatch_source_cancel(_timer);
}else{
_timeLeft--;
}
});
dispatch_resume(_timer);
}
}
@end
然后主要是用计时器的那个页面的代码:
#import "VC2.h"
#import "BMWNSTimer.h"
@interface VC2 ()
@property (nonatomic,strong) UIButton *timeBtn;
@property (nonatomic,assign) int timeout;
@property (nonatomic,strong) dispatch_source_t timer;
@end
@implementation VC2
- (void)viewDidLoad {
[super viewDidLoad];
self.view.backgroundColor = [UIColor whiteColor];
// Do any additional setup after loading the view.
_timeBtn = [[UIButton alloc]initWithFrame:CGRectMake(100, 100, 100, 40)];
[_timeBtn addTarget:self action:@selector(cutdown) forControlEvents:UIControlEventTouchUpInside];
[_timeBtn setTitle:@"开始倒计时" forState:UIControlStateNormal];
[_timeBtn setTitleColor:[UIColor whiteColor] forState:UIControlStateNormal];
_timeBtn.backgroundColor = [UIColor redColor];
[self.view addSubview:_timeBtn];
}
-(void)cutdown{
_timeout = 10;
_timeBtn.userInteractionEnabled=NO;
[self startTime];
}
-(void)startTime{
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
_timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0,queue);
dispatch_source_set_timer(_timer, DISPATCH_TIME_NOW, 1.0 * NSEC_PER_SEC, 1.0 * NSEC_PER_SEC);
dispatch_source_set_event_handler(_timer, ^{
if (self->_timeout <= 0) {
dispatch_source_cancel(self->_timer);
dispatch_async(dispatch_get_main_queue(), ^{
[self->_timeBtn setTitle:@"重新获取" forState:UIControlStateNormal];
self->_timeBtn.userInteractionEnabled = YES;
self->_timeBtn.backgroundColor = [UIColor blueColor];
});
}else {
dispatch_async(dispatch_get_main_queue(), ^{
[self->_timeBtn setTitle:[NSString stringWithFormat:@"%d秒",self->_timeout] forState:UIControlStateNormal];
self->_timeBtn.enabled = YES;
self->_timeBtn.backgroundColor = [UIColor lightGrayColor];
});
self->_timeout--;
NSLog(@"%d",self->_timeout);
}
});
dispatch_resume(_timer);
}
- (void)viewWillDisappear:(BOOL)animated
{
if (_timeout > 0) {
BMWNSTimer *timer = [BMWNSTimer sharedTimerManager];
timer.timeLeft = _timeout;
timer.from = from1;
[timer countDown];
}
}
- (void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
BMWNSTimer *timer = [BMWNSTimer sharedTimerManager];
int time = timer.timeLeft;
if (time >0 && (timer.from == from1)) {
_timeout = time;
_timeBtn.userInteractionEnabled=NO;
[self startTime];
} else {
_timeBtn.enabled=YES;
}
}
@end
大概就是这些了,这里面需要用到GCD计时器的知识,之前也没用过,看到别人这么用,就自己亲自试了一下,模仿是学习的第一步.
