在NSUserDefaults中保存图像？ [英] Save images in NSUserDefaults?

问题描述

是否可以将图像保存为 NSUserDefaults 作为对象，然后检索以供进一步使用？

Is it possible to save images into NSUserDefaults as an object and then retrieve for further use?

推荐答案

注意！如果您在iOS8 / XCODE6下工作，请查看我的更新

对于那些仍在寻找答案的人来说，这是保存图像的可取方式的代码在NSUserDefaults中。您不应该将图像数据直接保存到NSUserDefaults中！

For those who still looking for answer here is code of "advisable" way to save image in NSUserDefaults. You SHOULD NOT save image data directly into NSUserDefaults!

写入数据：

// Get image data. Here you can use UIImagePNGRepresentation if you need transparency
NSData *imageData = UIImageJPEGRepresentation(image, 1);

// Get image path in user's folder and store file with name image_CurrentTimestamp.jpg (see documentsPathForFileName below)
NSString *imagePath = [self documentsPathForFileName:[NSString stringWithFormat:@"image_%f.jpg", [NSDate timeIntervalSinceReferenceDate]]];

// Write image data to user's folder
[imageData writeToFile:imagePath atomically:YES];

// Store path in NSUserDefaults
[[NSUserDefaults standardUserDefaults] setObject:imagePath forKey:kPLDefaultsAvatarUrl];

// Sync user defaults
[[NSUserDefaults standardUserDefaults] synchronize];

读取数据：

NSString *imagePath = [[NSUserDefaults standardUserDefaults] objectForKey:kPLDefaultsAvatarUrl];
if (imagePath) {
    self.avatarImageView.image = [UIImage imageWithData:[NSData dataWithContentsOfFile:imagePath]];
}

documentsPathForFileName：

- (NSString *)documentsPathForFileName:(NSString *)name {
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsPath = [paths objectAtIndex:0];

    return [documentsPath stringByAppendingPathComponent:name];
}

适用于iOS8 / XCODE6
As下面的评论中提到的tmr和DevC存在xcode6 / ios8的问题。 xcode5和xcode 6安装过程之间的区别在于xcode6 在xcode中每次运行后更改应用程序UUID （请参阅路径中的高亮部分：/ var / mobile / Containers / Data / Application / B0D49CF5- 8FBE-4F14-87AE-FA8C16A678B1 /Documents/image.jpg）。

For iOS8/XCODE6 As tmr and DevC mentioned in comments below there is a problem with xcode6/ios8. The difference between xcode5 and xcode 6 installation process is that xcode6 changes apps UUID after each run in xcode (see hightlighted part in path: /var/mobile/Containers/Data/Application/B0D49CF5-8FBE-4F14-87AE-FA8C16A678B1/Documents/image.jpg).

所以有2种解决方法：

1. 跳过这个问题，因为一旦安装在真实设备上的应用程序，它永远不会改变UUID（事实上它确实如此，但它是新的应用程序）


2. 保存所需文件夹的相对路径（在我们的例子中是应用程序的根目录）

这是快速版本的代码作为奖励（第二种方法） ）：

Here is swift version of code as a bonus (with 2nd approach):

写入数据：

let imageData = UIImageJPEGRepresentation(image, 1)
let relativePath = "image_\(NSDate.timeIntervalSinceReferenceDate()).jpg"
let path = self.documentsPathForFileName(relativePath)
imageData.writeToFile(path, atomically: true)
NSUserDefaults.standardUserDefaults().setObject(relativePath, forKey: "path")
NSUserDefaults.standardUserDefaults().synchronize()

读取数据：

let possibleOldImagePath = NSUserDefaults.standardUserDefaults().objectForKey("path") as String?
if let oldImagePath = possibleOldImagePath {
    let oldFullPath = self.documentsPathForFileName(oldImagePath)
    let oldImageData = NSData(contentsOfFile: oldFullPath)
    // here is your saved image:
    let oldImage = UIImage(data: oldImageData)
}

documentsPathForFileName：

func documentsPathForFileName(name: String) -> String {
    let paths = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true);
    let path = paths[0] as String;
    let fullPath = path.stringByAppendingPathComponent(name)

    return fullPath
}

这篇关于在NSUserDefaults中保存图像？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！