1、RunLoop基础知识
首先我们先简单的来说一下，我们都知道程序启动的时候去走进main函数，在main用AppDelegate作为入口并遵守代理，这样就会进入AppDelegate的代理方法中，如didFinishLaunchingWithOptions等方法。当走进main函数的时候，系统默认会开启一个运行循环并且是死循环也就是我们这节要说的RunLoop。
那RunLoop它干了什么事？
1、负责监听事件(网络、时钟、触摸等)
2、如果没有事件发生，它会进入休眠状态
3、渲染界面，在一次循环中进行所有的渲染
1、NSTimer
NSTimer是苹果官方封装的一个倒计时类，使用起来比较简单。
//
// ViewController.m
// RAC_Timer
//
// Created by JM on 2018/4/21.
// Copyright © 2018年 JM. All rights reserved.
//
#import "ViewController.h"
@interface ViewController ()
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
[NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(timerDown) userInfo:nil repeats:YES];
}
- (void)timerDown {
static int i = 0;
i++;
NSLog(@"%d", i);
}
@end
控制台打印结果
2018-04-21 23:42:12.800474+0800 RAC_Timer[49953:2092718] 1
2018-04-21 23:42:13.801108+0800 RAC_Timer[49953:2092718] 2
2018-04-21 23:42:14.800973+0800 RAC_Timer[49953:2092718] 3
2018-04-21 23:42:15.800927+0800 RAC_Timer[49953:2092718] 4
2018-04-21 23:42:16.800965+0800 RAC_Timer[49953:2092718] 5
2018-04-21 23:42:17.800378+0800 RAC_Timer[49953:2092718] 6
2018-04-21 23:42:18.800847+0800 RAC_Timer[49953:2092718] 7
2018-04-21 23:42:19.799809+0800 RAC_Timer[49953:2092718] 8
2018-04-21 23:42:20.800715+0800 RAC_Timer[49953:2092718] 9
2018-04-21 23:42:21.799573+0800 RAC_Timer[49953:2092718] 10
2、NSTimer(RunLoop)
下面我们用RunLoop的方式来添加一下
下面有一个侧重点
1、NSDefaultRunLoopMode 为默认模式
2、UITrackingRunLoopMode 为UI模式，也就是说如果你创建该类型的RunLoop，它就只能被UI事件唤醒
3、NSRunLoopCommonModes 为占位模式，也就是说只要设置了该模式它就会同时通知默认模式以及UI模式
//
// ViewController.m
// RAC_Timer
//
// Created by JM on 2018/4/21.
// Copyright © 2018年 JM. All rights reserved.
//
#import "ViewController.h"
@interface ViewController ()
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
// [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(timerDown) userInfo:nil repeats:YES];
NSTimer *timer = [NSTimer timerWithTimeInterval:1.0 target:self selector:@selector(timerDown) userInfo:nil repeats:YES];
[[NSRunLoop currentRunLoop] addTimer:timer forMode:NSDefaultRunLoopMode];
}
- (void)timerDown {
static int i = 0;
i++;
NSLog(@"%d", i);
}
@end
控制台打印结果
2018-04-22 01:19:16.039742+0800 RAC_Timer[51955:2174228] 1
2018-04-22 01:19:17.039835+0800 RAC_Timer[51955:2174228] 2
2018-04-22 01:19:18.039767+0800 RAC_Timer[51955:2174228] 3
2018-04-22 01:19:19.039715+0800 RAC_Timer[51955:2174228] 4
2018-04-22 01:19:20.039490+0800 RAC_Timer[51955:2174228] 5
2018-04-22 01:19:21.038807+0800 RAC_Timer[51955:2174228] 6
2018-04-22 01:19:22.039854+0800 RAC_Timer[51955:2174228] 7
2018-04-22 01:19:23.038787+0800 RAC_Timer[51955:2174228] 8
2018-04-22 01:19:24.039777+0800 RAC_Timer[51955:2174228] 9
2018-04-22 01:19:25.039236+0800 RAC_Timer[51955:2174228] 10
在开发中我们常常会把耗时操作放到子线程，像定时器这种东西我们也一般都是放在子线程的，但是会发现NSTimer在子线程中无效，我们对创建定时器的代码做如下修改:
//创建子线程
NSThread *thread = [[NSThread alloc] initWithBlock:^{
NSLog(@"%@",[NSThread currentThread]);
NSTimer *timer = [NSTimer timerWithTimeInterval:1.0 target:self selector:@selector(timerDown) userInfo:nil repeats:YES];
[[NSRunLoop currentRunLoop] addTimer:timer forMode:NSDefaultRunLoopMode];
}];
//启动线程
[thread start];
控制台打印
2018-04-22 01:32:10.741969+0800 RAC_Timer[52318:2191101] <NSThread: 0x60400046e740>{number = 3, name = (null)}
在上述代码中我们发现并没有执行定时器方法，这是为什么呢！因为在子线程代码块结束的时候该线程被销毁了，所以就不会进入定时器方法也就是timerDown中。
那么该如何解决？
在上面的代码中我们发现有把定时器放在RunLoop中，但为什么还是失效呢！因为手动创建RunLoop默认是不运行的，我们需要运行RunLoop，如下
//创建子线程
NSThread *thread = [[NSThread alloc] initWithBlock:^{
NSLog(@"%@",[NSThread currentThread]);
NSTimer *timer = [NSTimer timerWithTimeInterval:1.0 target:self selector:@selector(timerDown) userInfo:nil repeats:YES];
[[NSRunLoop currentRunLoop] addTimer:timer forMode:NSDefaultRunLoopMode];
//开启RunLoop循环
[[NSRunLoop currentRunLoop] run];
}];
//启动线程
[thread start];
控制台打印
2018-04-22 01:41:14.998636+0800 RAC_Timer[52531:2203640] <NSThread: 0x604000272040>{number = 3, name = (null)}
2018-04-22 01:41:16.002548+0800 RAC_Timer[52531:2203640] 1
2018-04-22 01:41:17.000635+0800 RAC_Timer[52531:2203640] 2
2018-04-22 01:41:18.000488+0800 RAC_Timer[52531:2203640] 3
2018-04-22 01:41:19.001231+0800 RAC_Timer[52531:2203640] 4
2018-04-22 01:41:20.003273+0800 RAC_Timer[52531:2203640] 5
2018-04-22 01:41:21.001323+0800 RAC_Timer[52531:2203640] 6
2018-04-22 01:41:22.001346+0800 RAC_Timer[52531:2203640] 7
2018-04-22 01:41:23.001389+0800 RAC_Timer[52531:2203640] 8
2018-04-22 01:41:24.004123+0800 RAC_Timer[52531:2203640] 9
2018-04-22 01:41:25.001335+0800 RAC_Timer[52531:2203640] 10
3、GCD实现倒计时
//
// ViewController.m
// RAC_Timer
//
// Created by JM on 2018/4/21.
// Copyright © 2018年 JM. All rights reserved.
//
#import "ViewController.h"
@interface ViewController ()
/** timer */
@property (nonatomic, strong) dispatch_source_t timer;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
//GCD设置timer
dispatch_source_t timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, dispatch_get_global_queue(0, 0));
//GCD时间
dispatch_source_set_timer(timer, DISPATCH_TIME_NOW, 1.0 * NSEC_PER_SEC, 0);
dispatch_source_set_event_handler(timer, ^{
NSLog(@"%@", [NSThread currentThread]);
});
//启动
dispatch_resume(timer);
_timer = timer;
}
@end
控制台打印
2018-04-22 23:33:26.233998+0800 RAC_Timer[57174:2326547] <NSThread: 0x600000467180>{number = 3, name = (null)}
2018-04-22 23:33:27.234961+0800 RAC_Timer[57174:2326550] <NSThread: 0x604000467680>{number = 4, name = (null)}
2018-04-22 23:33:28.234041+0800 RAC_Timer[57174:2326550] <NSThread: 0x604000467680>{number = 4, name = (null)}
2018-04-22 23:33:29.234098+0800 RAC_Timer[57174:2326550] <NSThread: 0x604000467680>{number = 4, name = (null)}
2018-04-22 23:33:30.234248+0800 RAC_Timer[57174:2326550] <NSThread: 0x604000467680>{number = 4, name = (null)}
4、RAC实现倒计时
//rac实现倒计时
[[RACSignal interval:1.0 onScheduler:[RACScheduler scheduler]] subscribeNext:^(NSDate * _Nullable x) {
NSLog(@"%@", [NSThread currentThread]);
}]
控制台打印
2018-04-22 23:33:26.233998+0800 RAC_Timer[57174:2326547] <NSThread: 0x600000467180>{number = 3, name = (null)}
2018-04-22 23:33:27.234961+0800 RAC_Timer[57174:2326550] <NSThread: 0x604000467680>{number = 4, name = (null)}
2018-04-22 23:33:28.234041+0800 RAC_Timer[57174:2326550] <NSThread: 0x604000467680>{number = 4, name = (null)}
2018-04-22 23:33:29.234098+0800 RAC_Timer[57174:2326550] <NSThread: 0x604000467680>{number = 4, name = (null)}
2018-04-22 23:33:30.234248+0800 RAC_Timer[57174:2326550] <NSThread: 0x604000467680>{number = 4, name = (null)}
demo源代码已放置GitHub地址https://github.com/JunAILiang/RAC_Demo
联系我:
qq: 1245424073
微信: liujunmin6980
