ios - 设置下载 NSData 的进度条

Question

NSURL *url = [NSURL URLWithString:@"http://i0.kym-cdn.com/entries/icons/original/000/005/545/OpoQQ.jpg?1302279173"]; 
NSData *data = [NSData dataWithContentsOfURL:url]; 
imageView.image = [[[UIImage imageWithData:data];

我想在下载时设置进度条。

Answer 1

举一个更详细的例子：

在你的 .h 文件中做

@interface YourClass : YourSuperclass<NSURLConnectionDataDelegate>

在你的 .m 文件中做

@property (nonatomic) NSMutableData *imageData;
@property (nonatomic) NSUInteger totalBytes;
@property (nonatomic) NSUInteger receivedBytes;

在某处打电话

NSURL *url = [NSURL URLWithString:@"http://i0.kym-cdn.com/entries/icons/original/000/005/545/OpoQQ.jpg?1302279173"];
NSURLRequest *request = [NSURLRequest requestWithURL:url];
NSURLConnection *connection = [[NSURLConnection alloc] initWithRequest:request delegate:self startImmediately:YES];

并实现委托方法

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *) urlResponse;
    NSDictionary *dict = httpResponse.allHeaderFields;
    NSString *lengthString = [dict valueForKey:@"Content-Length"];
    NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];
    NSNumber *length = [formatter numberFromString:lengthString];
    self.totalBytes = length.unsignedIntegerValue;

    self.imageData = [[NSMutableData alloc] initWithCapacity:self.totalBytes];
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    [self.imageData appendData:data];
    self.receivedBytes += data.length;

    // Actual progress is self.receivedBytes / self.totalBytes
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    imageView.image = [UIImage imageWithData:self.imageData];
}

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    //handle error
}

Answer 2

使用该方法无法获得进度回调。

您需要使用NSURLConnectionand NSURLConnectionDataDelegate。

NSURLConnectionthen 异步运行并将回调发送给它的委托。

主要看的是...

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response;
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error;
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data;

和

- (void)connectionDidFinishLoading:(NSURLConnection *)connection;

这些都用于获取连接以完成您已经在做的事情。

编辑

实际上，请参阅下面的 Marc 的回答。它是正确的。

Answer 3

您可以使用 MBProgress Hud 类来加载视图。您只能从此处下载两个类：- https://github.com/jdg/MBProgressHUD 在您要加载数据的类中编写此代码后示例：在您的 viewDidLoad 中您编写此代码

- (void) viewDidLoad
{
    MBProgressHud *spinner =  [MBProgressHUD showHUDAddedTo:self.view animated:YES];

        spinner.mode = MBProgressHUDModeCustomView;

        [spinner setLabelText:@"Loading....."];

        [spinner setLabelFont:[UIFont systemFontOfSize:15]];

        [spinner show:YES];

        [self performSelectorInBackground:@selector(getData) withObject:nil];
}

- (void) getData
{
     NSURL *url = [NSURL URLWithString:@"http://i0.kym-cdn.com/entries/icons/original/000/005/545/OpoQQ.jpg?1302279173"]; 

        NSData *data = [NSData dataWithContentsOfURL:url]; 

        imageView.image = [[[UIImage imageWithData:data];

        [spinner hide:YES];

        [spinner removeFromSuperViewOnHide];
}