NSTimer定时器

NSTimer顾名思义是定时器，在iOS开发中可以用于设定一定的时间间隔，让其执行一段代码，常用于小游戏中的计时功能或者倒计时功能实现。

一、 初始化定时器（常用的2种）：

<code class="hljs objectivec has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;"><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//(1)</span>
+ (NSTimer *)timerWithTimeInterval:(<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">NSTimeInterval</span>)ti target:(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">id</span>)aTarget selector:(SEL)aSelector userInfo:(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">id</span>)userInfo repeats:(<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">BOOL</span>)yesOrNo;<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//(常用)</span>
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//(2)</span>
+ (NSTimer *)scheduledTimerWithTimeInterval:(<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">NSTimeInterval</span>)ti target:(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">id</span>)aTarget selector:(SEL)aSelector userInfo:(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">id</span>)userInfo repeats:(<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">BOOL</span>)yesOrNo;<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//（常用）</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li></ul>

两种初始化方法的区别：

1、timerWithTimeInterval这个类方法（1）创建出来的对象如果不用 addTimer: forMode方法手动加入主循环池中，将不会循环执行。并且如果不手动调用fair，则定时器不会启动。

2、scheduledTimerWithTimeInterval这个方法（2）不需要手动调用fair，会自动执行，并且自动加入主循环池。

代码：

<code class="hljs java has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;"><span class="hljs-javadoc" style="color: rgb(136, 0, 0); box-sizing: border-box;">/** 参数介绍
*   timerWithTimeInterval： 表示输入一个时间间隔对象，以秒为单位，一个>0的浮点类型的值，如果该值<0,系统会默认为0.1
*   target： 事件代理，一般填self
*   selector： 方法选择器，在时间间隔内，选择调用一个实例方法
*   userInfo： timer携带的信息（可以有timer1.userInfo取出）
*   repeats:是否循环 （YES-循环执行； NO-执行一次停止）
*   注意：当YES时，定时器会不断循环直至失效或被释放，当NO时，定时器会循环发送一次就失效。
*/</span>
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//初始化定时器timer1</span>
NSTimer *timer1 = [NSTimer timerWithTimeInterval:<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span> target:self selector:<span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@selector</span>(myFun:) userInfo:nil repeats:YES];
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//将定时器timer1加入主循环池中</span>
[[NSRunLoop mainRunLoop]addTimer:timer1 forMode:NSDefaultRunLoopMode];
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//开始循环定时器timer1</span>
[timer1 fire];

<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//初始化定时器timer2，并开始循环</span>
NSTimer *timer2 = [NSTimer scheduledTimerWithTimeInterval:<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span> target:self selector:<span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@selector</span>(myFun:) userInfo:@<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"abc"</span> repeats:YES]</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li></ul>

注意：将计数器的repeats设置为YES的时候，self的引用计数会加1。因此可能会导致self（即viewController）不能release，所以，必须在合适的时间或者viewWillAppear的时候，将计数器timer停止，否则可能会导致内存泄露。

二、NSTimer是否准确

答案是否定的，而且有时候你会发现实际的触发时间跟你想象的差距还比较大。NSTimer不是一个实时系统，因此不管是一次性的还是周期性的timer的实际触发事件的时间可能都会跟我们预想的会有出入。差距的大小跟当前我们程序的执行情况有关系，比如可能程序是多线程的，而你的timer只是添加在某一个线程的runloop的某一种指定的runloopmode中，由于多线程通常都是分时执行的，而且每次执行的mode也可能随着实际情况发生变化。

因此 timer不是一种实时的机制，会存在延迟，而且延迟的程度跟当前线程的执行情况有关。

还有一种情况是，将NSTimer添加进主运行循环，当主线程有较多的任务的时候（比如有较多的UI操作），那么主线程可能就会阻塞NSTimer，进而执行UI操作。

这类的解决办法是：将定时器用NSRunLoopCommonModes模式添加到主运行循环中。

<code class="hljs objectivec has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;">NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span> target:<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">self</span> selector:<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">@selector</span>(myLog:) userInfo:<span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">nil</span> repeats:<span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">YES</span>];
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//将其添加到主运行循环，防止阻塞</span>
[[NSRunLoop mainRunLoop] addTimer:timer forMode:NSRunLoopCommonModes];</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul>

三 关于内存释放

<code class="hljs objectivec has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">@property</span> (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">nonatomic</span>, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">strong</span>) NSTimer timer;

-(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span>)dealloc{
<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">NSLog</span>(@<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"dealloc"</span>);
}
- (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span>)viewDidLoad {
[<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">super</span> viewDidLoad];

<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//初始化定时器</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">self</span><span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">.timer</span>= [NSTimer scheduledTimerWithTimeInterval:<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span> target:<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">self</span> selector:<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">@selector</span>(myLog:) userInfo:<span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">nil</span> repeats:<span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">YES</span>];

<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//添加一个返回按钮</span>
<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">UIButton</span> *btn = [[<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">UIButton</span> alloc]initWithFrame:CGRectMake(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">50</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">50</span>)];
btn<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">.backgroundColor</span>=[<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">UIColor</span> blueColor];
[btn addTarget:<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">self</span> action:<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">@selector</span>(btnClick) forControlEvents:UIControlEventTouchUpInside];
[<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">self</span><span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">.view</span> addSubview:btn];
}

<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//监听按钮点击</span>
-(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span>)btnClick{
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//（要在控制器销毁之前将定时器移除，并清空），这样才能避免循环引用，防止内存泄露</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> ([<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">self</span><span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">.timer</span> isValid]) {
[<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">self</span><span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">.timer</span> invalidate];
}
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">self</span><span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">.timer</span>=<span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">nil</span>;
[<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">self</span> dismissViewControllerAnimated:<span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">YES</span> completion:<span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">nil</span>];
}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li></ul>

四 分类

在使用定时器的时候，可以给定时器创建一个分类，方便调用

<code class="hljs java has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;">#<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">import</span> <Foundation/Foundation.h>
<span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@interface</span> NSTimer (Extension)
<span class="hljs-javadoc" style="color: rgb(136, 0, 0); box-sizing: border-box;">/** 暂停定时器 */</span>
- (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span>)pauseTimer;
<span class="hljs-javadoc" style="color: rgb(136, 0, 0); box-sizing: border-box;">/** 重启定时器 */</span>
- (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span>)resumeTimer;
<span class="hljs-javadoc" style="color: rgb(136, 0, 0); box-sizing: border-box;">/** 销毁定时器 */</span>
- (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span>)removeTimer;
<span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@end</span>

<span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@implementation</span> NSTimer (Extension)
<span class="hljs-javadoc" style="color: rgb(136, 0, 0); box-sizing: border-box;">/** 暂停定时器 */</span>
-(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span>)pauseTimer{
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (![self isValid]) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> ;
[self setFireDate:[NSDate distantFuture]];
}

<span class="hljs-javadoc" style="color: rgb(136, 0, 0); box-sizing: border-box;">/** 重启定时器 */</span>
-(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span>)resumeTimer{
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (![self isValid]) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span>;
[self setFireDate:[NSDate date]];
}

<span class="hljs-javadoc" style="color: rgb(136, 0, 0); box-sizing: border-box;">/** 销毁定时器 */</span>
- (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span>)removeTimer{
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (![self isValid]) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span>;
[self invalidate];
self = nil;
}
<span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@end</span></code><code class="hljs java has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;"><span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;"><span style="font-family: 'microsoft yahei'; font-size: 14px;">
</span></span></code><code class="hljs java has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;"><span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;"><span style="font-family: 'microsoft yahei'; font-size: 14px;">
</span></span></code><code class="hljs java has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;"><span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;"><span style="font-family: 'microsoft yahei'; font-size: 14px;">
</span></span></code><code class="hljs java has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;"><span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;"><span style="font-family: 'microsoft yahei'; font-size: 14px;">总结：在使用定时器的时候，需要注意的就是内存释放的问题，关键是在合适的地方销毁定时器，防止其与控制器循环引用。还有就是 timer不是一种实时的机制，会存在延迟</span>
</span></code><code class="hljs java has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;"><span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;"><span style="font-family: 'microsoft yahei'; font-size: 14px;">
</span></span></code><code class="hljs java has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;"><span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;"><span style="font-family: 'microsoft yahei'; font-size: 14px;">
</span></span></code><code class="hljs java has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;"><span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;"><span style="font-family: 'microsoft yahei'; font-size: 14px;">
</span></span></code>