Question

我有一个将视频用作AVURLAsset并按时间间隔剪切视频的功能。我也有UIImageview IBOutlet叫做previewImageView，我想在执行函数时更改图像。在viewDidLoad中调用此函数。在函数执行完毕后，似乎只设置了previewImageView。我的代码在下面

NameError: name 'utf8' is not defined

我尝试按资源enter link description here

中的建议进行操作

Answer 1

您需要使图像无效才能立即刷新。只需调用UIView的setNeedsDisplay()函数。

dispatch_async(dispatch_get_main_queue()) 
{
  self.previewImageView.image = image
  self.previewImageView.setNeedsDisplay()
}

Answer 2

改为使用// call this method when you want to start updates - (void)startUpdates { _displayLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(doFrame)]; _displayLink.frameInterval = 1; [_displayLink addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode]; } // I'll let you guess - (void)stopUpdates { [_displayLink invalidate]; _displayLink = nil; } // In this method, do any needed updates. // Note that it will not necessarily be called every single frame, // so check actual time to decide what to display - (void)doFrame { }，它会尝试与屏幕刷新同步。

这是一些Objective-C代码，我将把它作为练习让读者将其转换为Swift。

<link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap.min.css" rel="stylesheet" />
<div class="container">
  <h3>With Reordering</h3>
  <div class="row">
    <div class="col-sm-4">
      <div class="alert alert-warning">UPPER 1
      </div>
    </div>
    <div class="col-sm-8">
      <div class="alert alert-danger">LOWER 1
      </div>
    </div>
  </div>
  <div class="row">
    <div class="col-sm-4 col-sm-push-8">


      <div class="alert alert-info">LOWER 2
      </div>
    </div>
    <div class="col-sm-8 col-sm-pull-4">
      <div class="alert alert-danger">UPPER 2

      </div>
    </div>
  </div>
</div>
<hr>
<div class="container">
  <h3>
    Without Reordering
  </h3>
  <div class="row">
    <div class="col-sm-4">
      <div class="alert alert-warning">UPPER 1
      </div>

    </div>
    <div class="col-sm-8">
      <div class="alert alert-danger">LOWER 1
      </div>
    </div>
  </div>
  <div class="row">
    <div class="col-sm-8">
      <div class="alert alert-danger">UPPER 2
      </div>
    </div>
    <div class="col-sm-4">
      <div class="alert alert-info">LOWER 2

      </div>
    </div>
  </div>
</div>

Answer 3

我通过在viewDidLoad中的后台线程中调用我的getImageAtInterval方法并调用＆＃34; previewImageView.image = image＆＃34;来解决了这个问题。在UIThread：）

在循环执行期间更改UIImageView UIImage

3 个答案: