iPhone dev - performSelector:withObject:afterDelay或NSTimer? [英] iPhone dev -- performSelector:withObject:afterDelay or NSTimer?
问题描述
要重复方法调用(或消息发送,我猜适当的术语是每个 x 秒),最好使用NSTimer(NSTimer的scheduledTimerWithTimeInterval:target:selector:userInfo:repeats:或者让方法在结尾处递归调用自身(使用performSelector:withObject:afterDelay)?后者不使用对象,但可能不太清晰/可读?另外,为了让您了解我正在做什么,它只是一个带有标签的视图,倒计时到午夜12点,当它变为0时,它会闪烁时间(00:00:00)并且永远发出哔哔声。
To repeat a method call (or message send, I guess the appropriate term is) every x seconds, is it better to use an NSTimer (NSTimer's scheduledTimerWithTimeInterval:target:selector:userInfo:repeats:) or to have the method recursively call itself at the end (using performSelector:withObject:afterDelay)? The latter doesn't use an object, but maybe its less clear/readable? Also, just to give you an idea of what I'm doing, its just a view with a label which counts down to 12:00 midnight, and when it gets to 0, it will blink the time (00:00:00) and play a beep sound forever.
谢谢。
编辑:同样,最好的方法是什么反复播放SystemSoundID(永远)?
编辑:我最终使用它来永远播放SystemSoundID:
also, what would be the best way to repeatedly play a SystemSoundID (forever) ? I ended up using this to play the SystemSoundID forever:
// Utilities.h
#import <Foundation/Foundation.h>
#import <AudioToolbox/AudioServices.h>
static void soundCompleted(SystemSoundID soundID, void *myself);
@interface Utilities : NSObject {
}
+ (SystemSoundID)createSystemSoundIDFromFile:(NSString *)fileName ofType:(NSString *)type;
+ (void)playAndRepeatSystemSoundID:(SystemSoundID)soundID;
+ (void)stopPlayingAndDisposeSystemSoundID;
@end
// Utilities.m
#import "Utilities.h"
static BOOL play;
static void soundCompleted(SystemSoundID soundID, void *interval) {
if(play) {
[NSThread sleepForTimeInterval:(NSTimeInterval)interval];
AudioServicesPlaySystemSound(soundID);
} else {
AudioServicesRemoveSystemSoundCompletion(soundID);
AudioServicesDisposeSystemSoundID(soundID);
}
}
@implementation Utilities
+ (SystemSoundID)createSystemSoundIDFromFile:(NSString *)fileName ofType:(NSString *)type {
NSString *path = [[NSBundle mainBundle] pathForResource:fileName ofType:type];
SystemSoundID soundID;
NSURL *filePath = [NSURL fileURLWithPath:path isDirectory:NO];
AudioServicesCreateSystemSoundID((CFURLRef)filePath, &soundID);
return soundID;
}
+ (void)playAndRepeatSystemSoundID:(SystemSoundID)soundID interval:(NSTimeInterval)interval {
play = YES
AudioServicesAddSystemSoundCompletion(soundID, NULL, NULL,
soundCompleted, (void *)interval);
AudioServicesPlaySystemSound(soundID);
}
+ (void)stopPlayingAndDisposeSystemSoundID {
play = NO
}
@end
似乎工作正常..对于标签闪烁我会使用NSTimer我猜。
Seems to work fine.. And for the label blinking I'll use an NSTimer I guess.
推荐答案
计时器更适合严格定义的间隔。如果您的函数调用本身有延迟,则会失去准确性,因为它实际上并非同步到一个时间间隔。总是有时间运行实际的方法本身也会把时间间隔排除。
A timer is more suited to a strictly defined interval. You will lose accuracy if you have your function call itself with a delay because its not really synced to a time interval. There's always the time taken to run the actual method itself as well which puts the interval out.
坚持使用NSTimer,我会说。
Stick with an NSTimer, I'd say.
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