我正在尝试从网址http://a3.twimg.com/profile_images/414797877/05052008321_bigger.jpg
下载图片我使用以下代码，但图片未保存在设备中。我想知道我做错了什么。
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:@"http://a3.twimg.com/profile_images/414797877/05052008321_bigger.jpg"]];
[NSURLConnection connectionWithRequest:request delegate:self];
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *localFilePath = [documentsDirectory stringByAppendingPathComponent:@"pkm.jpg"];
NSData *thedata = NULL;
[thedata writeToFile:localFilePath atomically:YES];
UIImage *img = [[UIImage alloc] initWithData:thedata];
答案 0 :(得分：101)
我碰巧找到了你想要的东西。
从网址获取图片
-(UIImage *) getImageFromURL:(NSString *)fileURL {
UIImage * result;
NSData * data = [NSData dataWithContentsOfURL:[NSURL URLWithString:fileURL]];
result = [UIImage imageWithData:data];
return result;
}
保存图片
-(void) saveImage:(UIImage *)image withFileName:(NSString *)imageName ofType:(NSString *)extension inDirectory:(NSString *)directoryPath {
if ([[extension lowercaseString] isEqualToString:@"png"]) {
[UIImagePNGRepresentation(image) writeToFile:[directoryPath stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.%@", imageName, @"png"]] options:NSAtomicWrite error:nil];
} else if ([[extension lowercaseString] isEqualToString:@"jpg"] || [[extension lowercaseString] isEqualToString:@"jpeg"]) {
[UIImageJPEGRepresentation(image, 1.0) writeToFile:[directoryPath stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.%@", imageName, @"jpg"]] options:NSAtomicWrite error:nil];
} else {
NSLog(@"Image Save Failed\nExtension: (%@) is not recognized, use (PNG/JPG)", extension);
}
}
加载图片
-(UIImage *) loadImage:(NSString *)fileName ofType:(NSString *)extension inDirectory:(NSString *)directoryPath {
UIImage * result = [UIImage imageWithContentsOfFile:[NSString stringWithFormat:@"%@/%@.%@", directoryPath, fileName, extension]];
return result;
}
如何对
//Definitions
NSString * documentsDirectoryPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
//Get Image From URL
UIImage * imageFromURL = [self getImageFromURL:@"http://www.yourdomain.com/yourImage.png"];
//Save Image to Directory
[self saveImage:imageFromURL withFileName:@"My Image" ofType:@"png" inDirectory:documentsDirectoryPath];
//Load Image From Directory
UIImage * imageFromWeb = [self loadImage:@"My Image" ofType:@"png" inDirectory:documentsDirectoryPath];
答案 1 :(得分：35)
如果将theData设置为nil，您希望它写入磁盘的内容是什么？
您可以使用NSData* theData = [NSData dataWithContentsOfURL:yourURLHere];从磁盘加载数据，然后使用writeToFile:atomically:保存数据。如果您需要更多地控制加载过程或将其置于后台，请查看NSURLConnection的文档和相关指南。
答案 2 :(得分：9)
这是从网址下载图片并将该图片保存在设备中的代码，this是参考链接。
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:@"http://a3.twimg.com/profile_images/414797877/05052008321_bigger.jpg"]];
[NSURLConnection connectionWithRequest:request delegate:self];
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *localFilePath = [documentsDirectory stringByAppendingPathComponent:@"pkm.jpg"];
NSData *thedata = [NSData dataWithContentsOfURL:[NSURL URLWithString:@"http://a3.twimg.com/profile_images/414797877/05052008321_bigger.jpg"]];
[thedata writeToFile:localFilePath atomically:YES];
答案 3 :(得分：4)
从网址获取图片
-(UIImage *) getImageFromURL:(NSString *)fileURL { UIImage * result; NSData * data = [NSData dataWithContentsOfURL:[NSURL URLWithString:fileURL]]; result = [UIImage imageWithData:data]; return result; }
这对我很有用，但我遇到了CFData（商店）的内存问题。用autoreleasepool修复它：
-(UIImage *) getImageFromURL:(NSString *)fileURL {
@autoreleasepool {
UIImage * result;
NSData * data = [NSData dataWithContentsOfURL:[NSURL URLWithString:fileURL]];
result = [UIImage imageWithData:data];
return result;
}
}
答案 4 :(得分：2)
嗨很明显，您正在将NULL数据写入文件。
在你的代码语句NSData * thedata = NULL;表示您为数据分配NULL值。
您也正在将NULL数据写入文件。
请再次检查您的代码。
答案 5 :(得分：2)
由于我们现在使用的是IOS6，因此您不再需要将图像写入磁盘 从iOS5开始，您现在可以在coredata二进制属性上设置“允许外部存储”。 根据苹果发行说明，它意味着以下内容：
图像缩略图等小数据值可以有效地存储在 数据库，但大型照片或其他媒体最好直接处理 文件系统。您现在可以指定托管的值 对象属性可以存储为外部记录 - 请参阅setAllowsExternalBinaryDataStorage: 启用后，核心数据启发式决定是否按值计算 它应该直接在数据库中保存数据或将URI存储到 它为您管理的单独文件。你无法根据查询 如果使用此选项，则为二进制数据属性的内容。
答案 6 :(得分：2)
-(IBAction)BtnDwn:(id)sender
{
[self.actvityIndicator startAnimating];
NSURL *URL = [NSURL URLWithString:self.dataaArray];
NSURLRequest *request = [NSURLRequest requestWithURL:URL];
NSURLSession *session = [NSURLSession sharedSession];
NSURLSessionDownloadTask *downloadTask = [session downloadTaskWithRequest:request completionHandler:^(NSURL *location, NSURLResponse *response, NSError *error)
{
NSString *documentsPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) firstObject];
NSURL *documentsDirectoryURL = [NSURL fileURLWithPath:documentsPath];
NSURL *documentURL = [documentsDirectoryURL URLByAppendingPathComponent:[response suggestedFilename]];
BOOL exists = [[NSFileManager defaultManager] fileExistsAtPath:[documentURL path]];
if (exists)
{
NSLog(@"not created");
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Download"
message:@"sory,file already exists"
delegate:nil
cancelButtonTitle:@"cancel"
otherButtonTitles:nil];
[alert show];
}
else
{
[[NSFileManager defaultManager] moveItemAtURL:location toURL:documentURL error:nil];
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Download"
message:@"Succesfully downloaded"
delegate:nil
cancelButtonTitle:@"OK"
otherButtonTitles:nil];
[self.actvityIndicator stopAnimating];
NSLog(@"wait downloading......");
[alert show];
}
}];
[downloadTask resume];
}
答案 7 :(得分：1)
以下是在Swift中异步保存图像的方法：
requestImage("http://www.asdf.com/89asdf.gif") { (image) -> Void in
let myImage = image
}
func requestImage(url: String, success: (UIImage?) -> Void) {
requestURL(url, success: { (data) -> Void in
if let d = data {
success(UIImage(data: d))
}
})
}
func requestURL(url: String, success: (NSData?) -> Void, error: ((NSError) -> Void)? = nil) {
NSURLConnection.sendAsynchronousRequest(
NSURLRequest(URL: NSURL (string: url)!),
queue: NSOperationQueue.mainQueue(),
completionHandler: { response, data, err in
if let e = err {
error?(e)
} else {
success(data)
}
})
}
它作为我的仓库中的标准功能包括在内：
答案 8 :(得分：0)
以下是我如何向我的应用下载横幅的示例。我在后台下载图像，我的大多数应用程序都没有使用引用计数，所以我发布了对象。
- (void)viewDidLoad {
[super viewDidLoad];
[NSThread detachNewThreadSelector:@selector(loadImageInBackground) toTarget:self withObject:nil];
}
- (void) loadImageInBackground {
NSURL *url = [[NSURL alloc] initWithString:@"http://yourImagePath.png"];
NSData *data = [[NSData alloc] initWithContentsOfURL:url];
[url release];
UIImage *result = [[UIImage alloc] initWithData:data];
[data release];
UIImageView *banner_ImageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 320, 50)];
[self.view addSubview:banner_ImageView];
banner_ImageView.image = result;
[result release];
}