Question

我知道有一些解决方案可以在iPhone上保存和加载图像。但是没有一个对我有用。

例如，下面的链接有一个很棒的代码块，可以让你用一个唯一的密钥加载和保存UIImage，但是如果在该密钥下的图像，我无法知道如何使用此代码加载图像已经存在与否。

http://www.friendlydeveloper.com/2010/02/using-nsfilemanager-to-save-an-image-to-or-loadremove-an-image-from-documents-directory-coding/

//saving an image
- (void)saveImage:(UIImage*)image:(NSString*)imageName {
     NSData *imageData = UIImagePNGRepresentation(image); //convert image into .png format.
     NSFileManager *fileManager = [NSFileManager defaultManager];//create instance of NSFileManager
     NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); //create an array and store result of our search for the documents directory in it
     NSString *documentsDirectory = [paths objectAtIndex:0]; //create NSString object, that holds our exact path to the documents directory
     NSString *fullPath = [documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.png", imageName]]; //add our image to the path
     [fileManager createFileAtPath:fullPath contents:imageData attributes:nil]; //finally save the path (image)
     NSLog(@"image saved");
}

//removing an image
- (void)removeImage:(NSString*)fileName {
     NSFileManager *fileManager = [NSFileManager defaultManager];
     NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
     NSString *documentsDirectory = [paths objectAtIndex:0];
     NSString *fullPath = [documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.png", fileName]];
     [fileManager removeItemAtPath: fullPath error:NULL];
     NSLog(@"image removed");
}

//loading an image
- (UIImage*)loadImage:(NSString*)imageName {
     NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
     NSString *documentsDirectory = [paths objectAtIndex:0];
     NSString *fullPath = [documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.png", imageName]];
     return [UIImage imageWithContentsOfFile:fullPath];
}

如果你可以帮我解决这个问题，那将非常感激。我需要保存多个图像，并根据给定的密钥是否已存在加载它们。

Answer 1

如果您想获取具有唯一键的图像，请尝试使用UUID。这将始终为您提供具有唯一键的图像。例如，这里是使用UUID的示例..

- (NSString *)pathForImageFileWithPrefix:(NSString *)Prefix
{
    CFUUIDRef   uuid;
    CFStringRef uuidStr;
    uuid = CFUUIDCreate(NULL);
    uuidStr = CFUUIDCreateString(NULL, uuid);
    NSData *imageData = UIImageJPEGRepresentation(chosenImage, 1.0);
    NSArray* paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);   
    NSString* documentsDirectory = [paths objectAtIndex:0]; 
    result = [documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:@"%@_%@.png",Prefix, uuidStr]];
    [imageData writeToFile:result atomically:NO];
    CFRelease(uuidStr);
    CFRelease(uuid);
    return result;
}

Answer 2

如果我的问题正确，您想知道具有给定图像名称的文件是否已存在？然后你可以使用

bool fileExists = [NSFileManager defaultManager] fileExistsAtPath:filePath];

iPhone使用唯一键加载并保存多个图像？

2 个答案: