UILabel+AFNetworking 显示下载百分比

原文地址：UILabel+AFNetworking 显示下载百分比

用处：

利用AFNetworking做下载操作的时候，利用UILabel动态显示下载百分比，显示格式如下：百分比%。

如何实现：

我们调用AFNetworking做下载的时候，一般会创建一个NSURLSessionDownloadTask对象，调用AFURLSessionManager的方法：

- (NSURLSessionDownloadTask *)downloadTaskWithRequest:(NSURLRequest *)request
                                             progress:(NSProgress * __autoreleasing *)progress
                                          destination:(NSURL * (^)(NSURL *targetPath, NSURLResponse *response))destination
                                    completionHandler:(void (^)(NSURLResponse *response, NSURL *filePath, NSError *error))completionHandler;

NSURLSessionDownloadTask继承于NSURLSessionTask，我们向捕获下载进度，实际就是监听NSURLSessionTask上的countOfBytesReceived和state属性，实时改变UILabel的显示文案即可。

源码：

UILabel+AFNetworking.h

#import 

@interface UILabel (AFNetworking)

- (void)setProgressWithDownloadProgressOfTask:(NSURLSessionDownloadTask *)task;

- (void)removeProgressOfTaskInfo:(NSURLSessionDownloadTask *)task;

@end

UILabel+AFNetworking.m

#import "UILabel+AFNetworking.h"

static void * AFTaskCountOfBytesReceivedContext = &AFTaskCountOfBytesReceivedContext;

@implementation UILabel (AFNetworking)

- (void)setProgressWithDownloadProgressOfTask:(NSURLSessionDownloadTask *)task
{
    [task addObserver:self forKeyPath:@"state" options:(NSKeyValueObservingOptions)0 context:AFTaskCountOfBytesReceivedContext];
    [task addObserver:self forKeyPath:@"countOfBytesReceived" options:(NSKeyValueObservingOptions)0 context:AFTaskCountOfBytesReceivedContext];
}

- (void)removeProgressOfTaskInfo:(NSURLSessionDownloadTask *)task {
    if (task) {
        @try {
            [task removeObserver:self forKeyPath:@"state"];
            [task removeObserver:self forKeyPath:@"countOfBytesReceived"];
        } @catch (NSException *exception) {
            
        }
    }
}

#pragma mark - NSKeyValueObserving

- (void)observeValueForKeyPath:(NSString *)keyPath
                      ofObject:(id)object
                        change:(__unused NSDictionary *)change
                       context:(void *)context
{
    if (context == AFTaskCountOfBytesReceivedContext) {
        if ([keyPath isEqualToString:NSStringFromSelector(@selector(countOfBytesReceived))]) {
            if ([object countOfBytesExpectedToReceive] > 0) {
                dispatch_async(dispatch_get_main_queue(), ^{
                    CGFloat progressValue = (CGFloat)[object countOfBytesReceived] / (CGFloat)[object countOfBytesExpectedToReceive] * 100.0;
                    
                    NSString *progress = [NSString stringWithFormat:@"%lld%%", (int64_t)progressValue];
                    self.text = progress;
                });
            }
        }
        
        if ([keyPath isEqualToString:NSStringFromSelector(@selector(state))]) {
            if ([(NSURLSessionTask *)object state] == NSURLSessionTaskStateCompleted) {
                @try {
                    [object removeObserver:self forKeyPath:NSStringFromSelector(@selector(state))];
                    
                    if (context == AFTaskCountOfBytesReceivedContext) {
                        [object removeObserver:self forKeyPath:NSStringFromSelector(@selector(countOfBytesReceived))];
                    }
                }
                @catch (NSException * __unused exception) {}
            }
        }
    }
}
@end

用法：

[yourLabel setProgressWithDownloadProgressOfTask:yourDownloadTask];

监听到下载完成，会自动移除掉obersver，如果想在下载到一半的时候移除监听，调用：

[yourLabel removeProgressOfTaskInfo:yourDownloadTask];

项目需要，所以写了这样的一个Category，其实相应的还可以做上传的动态监测，AFNetworkging自己也有一个UIKit+AFNetworking的group下实现了很多UIKit下控件关于AFNetworking的Category，大家可以去看下啦~~