NSTimer 和runloop的问题，将timer加入到runloop----同时注意在viewwilldisappear里面设置为空和无效

timer创建之后，需要将timer加入到mainrunloop当中去，而不是加入到currentrunloop.虽然两者都能实现在timer运行的时候拖动界面或者进行其他的操作不会停止timer，但是currentrunloop会影响到当前控制器的比如代理方法的执行。而mainrunloop不会影响。==深层原因得慢慢看资料。

-(void)startTimer{
currentTime = 0;
timer =[NSTimer scheduledTimerWithTimeInterval:0.01 target:self selector:@selector(timeTick) userInfo:nil repeats:YES];

[[NSRunLoop mainRunLoop]addTimer:timer forMode:NSRunLoopCommonModes];
[timer fire];

//    NSRunLoop *runloop = [NSRunLoop currentRunLoop];
//    [runloop addTimer:timer forMode:NSRunLoopCommonModes];
//    [runloop run];

//    [NSRunLoop currentRunLoop]来获得当前线程的Runloop，并且调用
//    [runloop addTimer:timer forMode:NSDefaultRunLoopMode]方法将定时器添加到runloop中，最后一定不要忘记调用runloop的run
}

//这边不能忘记-----否则。。。。就哔了狗。

<p class="p1"><span class="s1">#pragma mark - </span><span class="s2">停止录音</span></p><p class="p2"><span class="s1">- (</span><span class="s3">void</span><span class="s1">)stopRecord{</span></p><p class="p3"><span class="s4">    [</span><span class="s5">timer</span><span class="s4"> </span><span class="s1">invalidate</span><span class="s4">];</span></p><p class="p2"><span class="s1">    </span><span class="s5">timer</span><span class="s1"> = </span><span class="s3">nil</span><span class="s1">;</span></p><p class="p4"><span class="s4">    [</span><span class="s1">recorder</span><span class="s4"> </span><span class="s1">stop</span><span class="s4">];</span></p><p class="p2"><span class="s1">}</span></p><p class="p5"><span class="s1"></span></p><p class="p2"><span class="s1">-(</span><span class="s3">void</span><span class="s1">)viewWillDisappear:(</span><span class="s3">BOOL</span><span class="s1">)animated{</span></p><p class="p5"><span class="s1">   </span></p><p class="p4"><span class="s4">    [</span><span class="s3">self</span><span class="s4"> </span><span class="s1">stopRecord</span><span class="s4">];</span></p><p class="p2"><span class="s1">}</span></p>