当我们使用GCD的dispatch_after的时候，我们是没办法手动终止的，这样如果想提前终止一段时间后的方法执行，就要我们进行重写这个方法， 直接上代码
在controller.m里
#import "MainViewController.h"
#import "SecondViewController.h"
typedef void(^PDDelayedBlockHandle)(BOOL cancel);
@interface MainViewController ()
@property (nonatomic, assign) PDDelayedBlockHandle delayedBlockHandle;
@end
dispatch_after重写的方法
staticPDDelayedBlockHandleperform_block_after_delay(CGFloatseconds,dispatch_block_tblock) {
if(block ==nil) {
returnnil;
}
__blockdispatch_block_tblockToExecute = [blockcopy];
__blockPDDelayedBlockHandledelayHandleCopy =nil;
PDDelayedBlockHandledelayHandle = ^(BOOLcancel) {
if(!cancel && blockToExecute) {
blockToExecute();
}
blockToExecute =nil;
delayHandleCopy =nil;
};
delayHandleCopy = [delayHandlecopy];
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, seconds * NSEC_PER_SEC), dispatch_get_main_queue(), ^{
if(nil!= delayHandleCopy) {
delayHandleCopy(NO);
}
});
returndelayHandleCopy;
}
dispatch_after终止方法
staticvoidcancel_delayed_block(PDDelayedBlockHandledelayedHandle) {
if(nil== delayedHandle) {
return;
}
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
delayedHandle(YES);
});
}
例子引用
- (void)viewDidLoad {
[super viewDidLoad];
self.title=@"111";
self.view.backgroundColor = [UIColor grayColor];
UIButton *btn = [UIButton buttonWithType:UIButtonTypeCustom];
btn.frame=CGRectMake(30,100,80,40);
btn.backgroundColor = [UIColor grayColor];
[btnaddTarget:self action:@selector(click) forControlEvents:UIControlEventTouchUpInside];
[btnsetTitle:@"我同意" forState:UIControlStateNormal];
[self.view addSubview:btn];
}
- (void)click{
_delayedBlockHandle = perform_block_after_delay(8, ^{
SecondViewController *sec = [[SecondViewController alloc] init];
[self.navigationController pushViewController:sec animated:NO];
});
UIButton *btn1 = [UIButton buttonWithType:UIButtonTypeCustom];
btn1.frame = CGRectMake(30, 200, self.view.frame.size.width - 60, 40);
btn1.backgroundColor = [UIColor grayColor];
[btn1addTarget:self action:@selector(toSecond) forControlEvents:UIControlEventTouchUpInside];
[btn1setTitle:@"8s后跳转页面，也可以点我跳转" forState:UIControlStateNormal];
[self.view addSubview:btn1];
}
- (void)toSecond{
cancel_delayed_block(_delayedBlockHandle);
SecondViewController *sec = [[SecondViewController alloc] init];
[self.navigationController pushViewController:sec animated:NO];
}
