drawViewHierarchyInRect导致VM CG图像内存泄漏

Question

我有一个函数，它接受界面的屏幕截图并将其保存到实例属性（称为self.interfaceScreenshot）。

-(void)takeInterfaceScreenshot{
   // Iterate over every window from back to front

   for (UIWindow *window in [[UIApplication sharedApplication] windows])
   {
       if (![window respondsToSelector:@selector(screen)] || [window screen] == [UIScreen mainScreen])
       {
           UIGraphicsBeginImageContext([window bounds].size);
           [[self view] drawViewHierarchyInRect:[window bounds] afterScreenUpdates:YES];
      }
  }

  UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
  UIGraphicsEndImageContext();

  if(self.interfaceScreenshot != nil){
      self.interfaceScreenshot = nil;
  }

  self.interfaceScreenshot = image;
}

但是我在Instruments Profiler中看到，每次调用此函数时，都会有一个额外的持久化实例泄漏在VM：CG Image部分的分配统计信息中：

我正在使用iOS7。

Answer 1

经过一些试验后，我发现错误是错误是在循环中有UIGraphicsBeginImageContext([window bounds].size);。这很好用：

-(void)takeInterfaceScreenshot{

  UIGraphicsBeginImageContext([window bounds].size);

  // Iterate over every window from back to front
  for (UIWindow *window in [[UIApplication sharedApplication] windows])
  {
      if (![window respondsToSelector:@selector(screen)] || [window screen] == [UIScreen mainScreen])
      {
         [[self view] drawViewHierarchyInRect:[window bounds] afterScreenUpdates:YES];
      }
   }

   UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
   UIGraphicsEndImageContext();

   if(self.interfaceScreenshot != nil){
       self.interfaceScreenshot = nil;
   }

   self.interfaceScreenshot = image;
}