NSTimer在IOS開(kāi)發(fā)中會(huì)經(jīng)常用到,尤其是小型游戲撤蟆,然而對(duì)于初學(xué)者時(shí)常會(huì)注意不到其中的內(nèi)存釋放問(wèn)題,將其基本用法總結(jié)如下:
一、初始化方法:有五種初始化方法斑响,分別是
+ (NSTimer *)timerWithTimeInterval:(NSTimeInterval)ti invocation:(NSInvocation *)invocation repeats:(BOOL)yesOrNo;
- (void)viewDidLoad {
[super viewDidLoad];
//初始化一個(gè)Invocation對(duì)象
NSInvocation * invo = [NSInvocation invocationWithMethodSignature:[[self class] instanceMethodSignatureForSelector:@selector(init)]];
[invo setTarget:self];
[invo setSelector:@selector(myLog)];
NSTimer * timer = [NSTimer timerWithTimeInterval:1 invocation:invo repeats:YES];
//加入主循環(huán)池中
[[NSRunLoop mainRunLoop]addTimer:timer forMode:NSDefaultRunLoopMode];
//開(kāi)始循環(huán)
[timer fire];
}
+ (NSTimer *)scheduledTimerWithTimeInterval:(NSTimeInterval)ti invocation:(NSInvocation *)invocation repeats:(BOOL)yesOrNo;
NSTimer * timer = [NSTimer scheduledTimerWithTimeInterval:1 invocation:invo repeats:YES];
+ (NSTimer *)timerWithTimeInterval:(NSTimeInterval)ti target:(id)aTarget selector:(SEL)aSelector userInfo:(id)userInfo repeats:(BOOL)yesOrNo;
NSTimer * timer = [NSTimer timerWithTimeInterval:1 target:self selector:@selector(myLog) userInfo:nil repeats:NO]
+ (NSTimer *)scheduledTimerWithTimeInterval:(NSTimeInterval)ti target:(id)aTarget selector:(SEL)aSelector userInfo:(id)userInfo repeats:(BOOL)yesOrNo;
NSTimer * timer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(myLog:) userInfo:@"123" repeats:YES]
- (instancetype)initWithFireDate:(NSDate *)date interval:(NSTimeInterval)ti target:(id)t selector:(SEL)s userInfo:(id)ui repeats:(BOOL)rep
NSTimer * timer = [[NSTimer alloc]initWithFireDate:[NSDate distantPast] interval:1 target:self selector:@selector(myLog:) userInfo:nil repeats:YES];
[[NSRunLoop mainRunLoop]addTimer:timer forMode:NSDefaultRunLoopMode];
注意:這五種初始化方法的異同:
1、參數(shù)repeats是指定是否循環(huán)執(zhí)行钳榨,YES將循環(huán)舰罚,NO將只執(zhí)行一次。
2薛耻、timerWithTimeInterval這兩個(gè)類方法創(chuàng)建出來(lái)的對(duì)象如果不用 addTimer: forMode方法手動(dòng)加入主循環(huán)池中营罢,將不會(huì)循環(huán)執(zhí)行。并且如果不手動(dòng)調(diào)用fair昭卓,則定時(shí)器不會(huì)啟動(dòng)。
3瘟滨、scheduledTimerWithTimeInterval這兩個(gè)方法不需要手動(dòng)調(diào)用fair候醒,會(huì)自動(dòng)執(zhí)行,并且自動(dòng)加入主循環(huán)池杂瘸。
4倒淫、init方法需要手動(dòng)加入循環(huán)池,它會(huì)在設(shè)定的啟動(dòng)時(shí)間啟動(dòng)败玉。
二敌土、成員變量
@property (copy) NSDate *fireDate;
這是設(shè)置定時(shí)器的啟動(dòng)時(shí)間,常用來(lái)管理定時(shí)器的啟動(dòng)與停止
//啟動(dòng)定時(shí)器
timer.fireDate = [NSDate distantPast];
//停止定時(shí)器
timer.fireDate = [NSDate distantFuture];
@property (readonly) NSTimeInterval timeInterval;
這個(gè)是一個(gè)只讀屬性运翼,獲取定時(shí)器調(diào)用間隔時(shí)間返干。
@property NSTimeInterval tolerance;
這是7.0之后新增的一個(gè)屬性,因?yàn)镹STimer并不完全精準(zhǔn)血淌,通過(guò)這個(gè)值設(shè)置誤差范圍矩欠。
@property (readonly, getter=isValid) BOOL valid;
獲取定時(shí)器是否有效
@property (readonly, retain) id userInfo;
獲取參數(shù)信息
三财剖、關(guān)于內(nèi)存釋放
如果我們啟動(dòng)了一個(gè)定時(shí)器,在某個(gè)界面釋放前癌淮,將這個(gè)定時(shí)器停止躺坟,甚至置為nil,都不能是這個(gè)界面釋放乳蓄,原因是系統(tǒng)的循環(huán)池中還保有這個(gè)對(duì)象咪橙。所以我們需要這樣做:
-(void)dealloc{
NSLog(@"dealloc:%@",[self class]);
}
- (void)viewDidLoad {
[super viewDidLoad];
timer= [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(myLog:) userInfo:nil repeats:YES];
UIButton *btn = [[UIButton alloc]initWithFrame:CGRectMake(0, 0, 100, 100)];
btn.backgroundColor=[UIColor redColor];
[btn addTarget:self action:@selector(btn) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:btn];
}
-(void)btn{
if (timer.isValid) {
[timer invalidate];
}
timer=nil;
[self dismissViewControllerAnimated:YES completion:nil];
}
在官方文檔中我們可以看到 [timer invalidate]是唯一的方法將定時(shí)器從循環(huán)池中移除。