UIImageView和drawInRect有什么区别？ [英] what is the difference between UIImageView and drawInRect?

问题描述

我想在表格单元格中显示如此多的图像。我知道两种显示图像的方法。

一个是为UIImageView创建一个实例并显示它

  CGRect RECT = CGRectMake（X，Y，宽度，高度）; 
 UIImageView * image = [[UIImageView alloc] initWithFrame：rect]; 
 [image setImage：[UIImage imageNamed：@sample.jpg]]; 
  

另一种方法是，

  CGRect rect = CGRectMake（x，y，width，height）; 
 [[UIImage imageNamed：@sample.jpg] drawInRect：rect]; 
  

现在，我的问题是，这两者有什么区别？哪一个有效？还是其他一些功能比这更好？

提前致谢....

解决方案

使用 drawInRect：方法，CoreGraphics使用CPU将图像绘制到活动的 CGContext 中。假设你在 UIView 的 drawRect：方法中，这会将图像绘制到视图的缓冲区中。 / p>

UIImageView 使用分配给它的任何图像，因为它是后备缓冲区而不是使用较慢的的drawRect：。然后，当通过QuartzCore合成屏幕时，GPU直接引用此缓冲区。

I want to display so many images in table cells. I knew two methods to show an image.

One is creating an instance to UIImageView and show it

CGRect rect=CGRectMake(x,y,width,height);
UIImageView *image=[[UIImageView alloc]initWithFrame:rect];
[image setImage:[UIImage imageNamed:@"sample.jpg"]];

Another method is,

CGRect rect=CGRectMake(x,y,width,height);
[[UIImage imageNamed:@"sample.jpg"] drawInRect:rect];

Now, my question is, what is the difference between these two? Which one is efficient? Or someother function is available better than this?

Thanks in advance....

解决方案

Using the drawInRect: method has CoreGraphics draw the image into the active CGContext using the CPU. Assuming you're in a UIView's drawRect: method, this will paint the image into the view's buffer.

UIImageView uses whichever image is assigned to it as it's backing buffer instead of using the slower drawRect:. The GPU then references this buffer directly when the screen is composited via QuartzCore.

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