我可以从URL加载UIImage吗？ [英] Can I load a UIImage from a URL?

问题描述

我有一个图像的URL（从UIImagePickerController获取）但我不再拥有内存中的图像（该URL是从以前的应用程序运行中保存的）。我可以再次从URL重新加载UIImage吗？

I have a URL for an image (got it from UIImagePickerController) but I no longer have the image in memory (the URL was saved from a previous run of the app). Can I reload the UIImage from the URL again?

我看到UIImage有一个imageWithContentsOfFile：但我有一个URL。我可以使用NSData的dataWithContentsOfURL：来读取URL吗？

I see that UIImage has a imageWithContentsOfFile: but I have a URL. Can I use NSData's dataWithContentsOfURL: to read the URL?

根据@ Daniel的回答，我尝试了以下代码，但它不起作用...

based on @Daniel's answer I tried the following code but it doesn't work...

NSLog(@"%s %@", __PRETTY_FUNCTION__, photoURL);     
if (photoURL) {
    NSURL* aURL = [NSURL URLWithString:photoURL];
    NSData* data = [[NSData alloc] initWithContentsOfURL:aURL];
    self.photoImage = [UIImage imageWithData:data];
    [data release];
}

当我运行时，控制台显示：

When I ran it the console shows:

-[PhotoBox willMoveToWindow:] file://localhost/Users/gary/Library/Application%20Support/iPhone%20Simulator/3.2/Media/DCIM/100APPLE/IMG_0004.JPG
*** -[NSURL length]: unrecognized selector sent to instance 0x536fbe0
*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[NSURL length]: unrecognized selector sent to instance 0x536fbe0'

查看调用堆栈，我正在调用URLWithString，调用URLWithString：relativeToURL：，然后是initWithString：relativeToURL：，然后是_CFStringIsLegalURLString，然后是CFStringGetLength，然后是 forwarding_prep_0 ，然后是转发，然后是 - [NSObject doesNotRecognizeSelector]。

Looking at the call stack, I'm calling URLWithString, which calls URLWithString:relativeToURL:, then initWithString:relativeToURL:, then _CFStringIsLegalURLString, then CFStringGetLength, then forwarding_prep_0, then forwarding, then -[NSObject doesNotRecognizeSelector].

为什么我的NSString（photoURL的地址是0x536fbe0）没有响应长度？为什么它说它不响应 - [NSURL长度]？难道不知道param是NSString而不是NSURL吗？

Any ideas why my NSString (photoURL's address is 0x536fbe0) doesn't respond to length? Why does it say it doesn't respond to -[NSURL length]? Doesn't it know that param is an NSString, not a NSURL?

好的，代码的唯一问题是字符串到URL的转换。如果我硬编码字符串，其他一切工作正常。所以我的NSString有问题，如果我无法弄清楚，我想这应该是另一个问题。插入此行（我从上面的控制台日志粘贴路径），它工作正常：

OK, the only problem with the code is the string to URL conversion. If I hardcode the string, everything else works fine. So something is wrong with my NSString and if I can't figure it out, I guess that should go in as a different question. With this line inserted (I pasted the path from the console log above), it works fine:

photoURL = @"file://localhost/Users/gary/Library/Application%20Support/iPhone%20Simulator/3.2/Media/DCIM/100APPLE/IMG_0004.JPG";

推荐答案

你可以这样做（同步，但紧凑）：

You can do it this way (synchronously, but compact):

UIImage *image = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:MyURL]]];

更好的方法是使用Apple的LazyTableImages来保持交互性。

A much better approach is to use Apple's LazyTableImages to preserve interactivity.

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