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iPhone开发-性能选择器:带对象:延迟后还是NSTimer?

repeat tail-recursion nstimer iphone

mk12 · 技术社区 · 17 年前

// 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

似乎工作得很好。。对于标签闪烁,我想我会使用NSTimer。

3 回复 | 直到 17 年前

Nick Bedford 17 年前

我会说,坚持使用NSTimer。

Kendall Helmstetter Gelner 17 年前

为了对其他答案稍作补充,递归调用的情况是,调用可能需要未知的时间——比如你正在用少量数据重复调用一个web服务,直到完成。每次调用可能需要一些未知的时间,因此您可以让代码在web调用返回之前什么都不做,然后发送下一批,直到没有更多数据需要发送,并且代码不会再次调用自己。

Elliot 17 年前

由于您的应用程序依赖于时间精度(即它需要每秒执行一次),因此NSTimer会更好。方法本身需要一些时间来执行,NSTimer也可以(只要你的方法每秒调用一次,时间不到1秒)。

要反复播放声音,您可以设置一个完成回调并在那里重放声音:

SystemSoundID tickingSound;

...

AudioServicesAddSystemSoundCompletion(tickingSound, NULL, NULL, completionCallback, (void*) self);

...

static void completionCallback(SystemSoundID mySSID, void* myself) {
  NSLog(@"completionCallback");

  // You can use this when/if you want to remove the completion callback
  //AudioServicesRemoveSystemSoundCompletion(mySSID);

  // myself is the object that called set the callback, because we set it up that way above
  // Cast it to whatever object that is (e.g. MyViewController, in this case)
  [(MyViewController *)myself playSound:mySSID];
}