我试图在“启动”它后 2 秒运行一段代码。
我认为 NSTimer 可以做到这一点,但无法弄清楚。
可以使用 NSTimer,但另一种选择是使用performSelector:withObject:afterDelay: 它基本上就像稍后发生的方法调用(消息发送)。
此示例将在延迟后发送 doStuff: 消息:
[self performSelector:@selector(doStuff:) withObject:self afterDelay:2];
这会导致此方法在 2.0 秒后被调用:
-(void)doStuff:(id)sender
{
/// do something
}
以下将满足您的需要:
NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval: 2
target:self
selector:@selector(handleTimer:)
userInfo:nil
repeats:NO];
然后委托函数:
-(void)handleTimer: (NSTimer *) timer
{
//code
}
您还可以使用一些方便的代码:
NSObject+PerformBlock.h
@interface NSObject (PerformBlock)
- (void)performBlock:(void(^)(void))block waitUntilDone:(BOOL)wait;
- (void)performBlock:(void(^)(void))block afterDelay:(NSTimeInterval)delay;
- (void)performBlock:(void(^)(void))block repeatCount:(NSUInteger)repeatCount timeInteval:(NSTimeInterval)timeInterval;
@end
NSObject+PerformBlock.m
@interface NSObject (PerformBlockHidden)
- (void)performBlock:(void(^)(void))block;
@end
@implementation NSObject (PerformBlock)
- (void)performBlock:(void(^)(void))block {
block();
}
- (void)performBlock:(void(^)(void))block waitUntilDone:(BOOL)wait {
[self performSelector:@selector(performBlock:) onThread:nil withObject:[[block copy] autorelease] waitUntilDone:wait];
}
- (void)performBlock:(void(^)(void))block afterDelay:(NSTimeInterval)delay {
[self performSelector:@selector(performBlock:) withObject:[[block copy] autorelease] afterDelay:delay];
}
- (void)performBlock:(void(^)(void))block repeatCount:(NSUInteger)repeatCount timeInteval:(NSTimeInterval)timeInterval {
for (NSInteger repetition = 0; repetition < repeatCount; repetition++)
[self performBlock:block afterDelay:(repetition*timeInterval)];
}
@end
然后只需导入 NSObject+PerformBlock.h 并调用:
[myObject performBlock:^{
// Code you want to perform after 2secs
} afterDelay:2];
您应该能够将 设置NSTimeInterval
为 2.0 秒,并且它应该会在该时间后触发。你在看什么?您用来调用计时器的代码是什么?