首先这个要涉及到NSRunLoop和概念，我就简单的说一下。一个主线程，它在调用自己或其他类的函数的时候需要NSRunLoop，而主线程则默认有NSRunLoop。但是子线程没有，所以当子线程调用其他函数的时候会失效，如果我们开启NSRunLoop就能使用，这个NSRunLoop并不是我们创建出来的，而是去借用主线程的。
先上代码，再说一下
//
// ViewController.m
// BmobTest
//
// Created by shanreal-iOS on 2017/12/9.
// Copyright © 2017年 shanreal.LongZhenHao. All rights reserved.
//
#import "ViewController.h"
#import "TestBean.h"
#import "MyTableViewCell.h"
#import "DetailTableViewCell.h"
@interface ViewController ()
@property(nonatomic,strong)UIButton* btn;
@property(nonatomic,strong)UIButton* btn2;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
_btn = [[UIButton alloc]initWithFrame:CGRectMake(20, 20, 100, 30)];
[_btn setTitle:@"button" forState:UIControlStateNormal];
[_btn setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
_btn.font = [UIFont systemFontOfSize:20];
[_btn addTarget:self action:@selector(btnClick) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:_btn];
_btn2 = [[UIButton alloc]initWithFrame:CGRectMake(20, 60, 100, 30)];
[_btn2 setTitle:@"two" forState:UIControlStateNormal];
[_btn2 setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
_btn2.font = [UIFont systemFontOfSize:20];
[_btn2 addTarget:self action:@selector(btn2Click) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:_btn2];
}
-(void)btnClick{
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
[self performSelector:@selector(backGroundThread) onThread:[NSThread currentThread] withObject:nil waitUntilDone:NO];
NSRunLoop *runLoop = [NSRunLoop currentRunLoop];
[runLoop run];
});
}
- (void)backGroundThread{
NSLog(@"%u",[NSThread isMainThread]);
NSLog(@"execute %s",__FUNCTION__);
}
-(void)btn2Click{
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
NSTimer *myTimer = [NSTimer scheduledTimerWithTimeInterval:0.5 target:self selector:@selector(timerAction) userInfo:nil repeats:YES];
[myTimer fire];
NSRunLoop *runLoop = [NSRunLoop currentRunLoop];
[runLoop run];
});
}
- (void)timerAction{
NSLog(@"timer action");
}
@end
这个NSRunLoop一定要放在执行的函数后面，如果不这样做，可能不会执行函数。我在想可能是跳转函数后，才会需要NSRunLoop，而不是跳转前去准备。