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

问题描述

是否可以将图像作为对象保存到 NSUserDefaults 中，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，请在下面查看我的更新

对于那些仍然在这里寻找答案的人来说，这是在 NSUserDefaults 中保存图像的建议"方式的代码.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];
}

对于 iOS8/XCODE6正如 tmr 和 DevC 在下面的评论中提到的，xcode6/ios8 存在问题.xcode5 和 xcode 6 安装过程的区别在于 xcode6 每次在 xcode 中运行后更改应用程序 UUID(请参阅路径中突出显示的部分:/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).

所以有两种解决方法:

1. 跳过这个问题，因为一旦应用安装在真实设备上，它就永远不会改变 UUID(实际上它会改变，但它是新应用)
2. 保存所需文件夹的相对路径(在我们的例子中是应用的根目录)

这是作为奖励的 swift 代码版本(使用第二种方法):

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！