网编基础（4）网络下载音乐和视频

代码正文：

#import "ViewController.h"@interface ViewController ()<NSURLSessionDownloadDelegate>{    NSURLSessionDownloadTask *task;    NSURLSession *session;    NSData *savedData;}@property (weak, nonatomic) IBOutlet UIProgressView *progressBar;@end@implementation ViewController- (void)viewDidLoad {    [super viewDidLoad];}- (IBAction)downloadURLMp3:(UIButton *)sender {    //创建URL    NSURL *url = [NSURL URLWithString:@"http://www.itinge.com/music/3/9158.mp3"];    //创建网络请求    NSURLRequest *request = [NSURLRequest requestWithURL:url];    //创建网络会话    session = [NSURLSession sharedSession];    //创建网络会话加载任务    task = [session downloadTaskWithRequest:request completionHandler:^(NSURL * _Nullable location, NSURLResponse * _Nullable response, NSError * _Nullable error) {        //文件管理创建        NSFileManager *manager = [NSFileManager defaultManager];        //拼接本地沙盒路径存储地址        NSString *filePath = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents/music.mp3"];        //将下载的文件保存到本地路径        [manager moveItemAtURL:location toURL:[NSURL fileURLWithPath:filePath] error:NULL];        if (error) {            NSLog(@"下载歌曲出现错误");        }else {            NSLog(@"歌曲下载成功");        }    }];    //发起网络请求    [task resume];}- (IBAction)downloadURLMp4:(UIButton *)sender {    //创建URL    NSURL *url = [NSURL URLWithString:@"http://vf1.mtime.cn/Video/2012/04/23/mp4/120423212602431929.mp4"];    //创建网络请求    NSURLRequest *request = [[NSURLRequest alloc] initWithURL:url];    //创建网络会话配置对象    NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration];    //创建网络会话    session = [NSURLSession sessionWithConfiguration:configuration delegate:self delegateQueue:[NSOperationQueue mainQueue]];    //创建网络会话任务对象    task = [session downloadTaskWithRequest:request];    //发起网络请求    [task resume];}//开始下载就调用(不断的调用)- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didWriteData:(int64_t)bytesWritten totalBytesWritten:(int64_t)totalBytesWritten totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite {    /*     这个方法在下载的时候不断的调用     bytesWritten:本次传输下载了多少个字节     totalBytesWritten：目前已经下载了多少个字节     totalBytesExpectedToWrite：文件的总大小     */    //获取下载的百分比，计算进度条的值    CGFloat myValue = totalBytesWritten/(CGFloat)totalBytesExpectedToWrite;    _progressBar.progress = myValue;}- (IBAction)pauseAction:(UIButton *)sender {    //取消的时候，保存数据    [task cancelByProducingResumeData:^(NSData * _Nullable resumeData) {        savedData = resumeData;        task = nil;    }];}- (IBAction)continueAction:(UIButton *)sender {    //点击继续按钮，将暂停的时候保存的数据恢复下载    task = [session downloadTaskWithResumeData:savedData];    //再次发起网络请求    [task resume];}- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didFinishDownloadingToURL:(NSURL *)location {    NSLog(@"%@", location);    NSLog(@"下载成功");}@end