iOS下载之NSURLSessionDownloadTask

下载管理

DownloadManager.h

#import <Foundation/Foundation.h>

NS_ASSUME_NONNULL_BEGIN

typedef void(^DownloadProgressBlock)(float progress);
typedef void(^DownloadCompleteBlock)(BOOL success, NSString * _Nullable filePath, NSError * _Nullable error);

@interface DownloadManager : NSObject

- (void)downloadWithUrl:(NSURL *)url toPath:(NSString *)toPath progress:(DownloadProgressBlock)progress complete:(DownloadCompleteBlock)complete;

- (void)cancel;
- (void)suspend;
- (void)resume;

@end

DownloadManager.m

#import "DownloadManager.h"

@interface DownloadManager () <NSURLSessionDelegate>

@property (nonatomic, strong) NSURLSessionConfiguration *sessionConfiguration;
@property (nonatomic, strong) NSURLSession *session;
@property (nonatomic, strong) NSURLSessionDownloadTask *downloadTask;

@property (nonatomic, copy) DownloadProgressBlock progress;
@property (nonatomic, copy) DownloadCompleteBlock complete;

@property (nonatomic, strong) NSURL *fileUrl;
@property (nonatomic, strong) NSString *toPath;

@end

@implementation DownloadManager

#define ImageURL @"http://p3.so.qhimg.com/t01bddfda09bdfc39a3.jpg" //test

- (void)downloadWithUrl:(NSURL *)url toPath:(NSString *)toPath progress:(DownloadProgressBlock)progress complete:(DownloadCompleteBlock)complete
{
    NSURLSessionConfiguration *sessionConfiguration = [NSURLSessionConfiguration defaultSessionConfiguration];
    self.sessionConfiguration = sessionConfiguration;
        
    NSURLSession *downloadSession = [NSURLSession sessionWithConfiguration:self.sessionConfiguration delegate:self delegateQueue:[NSOperationQueue mainQueue]];
    self.session = downloadSession;
    
    //test
//    url = [NSURL URLWithString:ImageURL];
    
    NSURLRequest *request = [NSURLRequest requestWithURL:url];
    NSURLSessionDownloadTask *downloadTask =  [downloadSession downloadTaskWithRequest:request];
    self.downloadTask = downloadTask;
    
    self.fileUrl = url;
    self.toPath = toPath;
    self.progress = progress;
    self.complete = complete;
    
    [downloadTask resume];
}

- (void)cancel
{
    if (self.downloadTask) {
        [self.downloadTask cancel];
    }
}

- (void)suspend
{
    if (self.downloadTask) {
        [self.downloadTask suspend];
    }
}

- (void)resume
{
    if (self.downloadTask) {
        [self.downloadTask resume];
    }
}

#pragma mark - NSURLSessionDelegate

- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didWriteData:(int64_t)bytesWritten totalBytesWritten:(int64_t)totalBytesWritten totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite
{
    NSLog(@"app: bytesWritten=%@,totalBytesWritten=%@,totalBytesExpectedToWrite=%@",@(bytesWritten),@(totalBytesWritten),@(totalBytesExpectedToWrite));
    float progress = (float)totalBytesWritten/totalBytesExpectedToWrite;
    
    if (self.progress) {
        self.progress(progress);
    }
}

- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didFinishDownloadingToURL:(NSURL *)location
{
    NSLog(@"任务下载完成");
    if (self.progress) {
        self.progress(1.0);
    }
    
    //1 拼接文件全路径
    if (self.toPath.length) {
        if (self.toPath.lastPathComponent.length) {
            //do nothing
        } else {
            self.toPath = [self.toPath stringByAppendingPathComponent:downloadTask.response.suggestedFilename];
        }
    } else {
        //默认下载到/Library/Cache/SavedFiles
        NSString *cacheDir = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) firstObject];
        NSString *appDir = [cacheDir stringByAppendingPathComponent:@"SavedFiles"];
        self.toPath = [appDir stringByAppendingPathComponent:downloadTask.response.suggestedFilename];
    }
    
    //2 必须要剪切文件, 因为系统默认会删除
    if ([[NSFileManager defaultManager] fileExistsAtPath:self.toPath]) {
        [[NSFileManager defaultManager] removeItemAtPath:self.toPath error:nil];
    }
    //创建文件夹
    NSString *dir = [self.toPath stringByDeletingLastPathComponent];
    BOOL isDir = YES;
    if (![[NSFileManager defaultManager] fileExistsAtPath:dir isDirectory:&isDir]) {
        [[NSFileManager defaultManager] createDirectoryAtPath:dir withIntermediateDirectories:YES attributes:nil error:nil];
    }
    [[NSFileManager defaultManager]moveItemAtURL:location toURL:[NSURL fileURLWithPath:self.toPath] error:nil];
    NSLog(@"app: download ok, path:%@", self.toPath);
}

//无论是数据任务还是上传任务执行完之后都会执行该回调
- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error
{
    NSLog(@"整个任务完成");
    NSLog(@"app: download complete, error:%@", error);
    if (error) {
        // check if resume data are available
        if ([error.userInfo objectForKey:NSURLSessionDownloadTaskResumeData]) {
            NSData *resumeData = [error.userInfo objectForKey:NSURLSessionDownloadTaskResumeData];
            //通过之前保存的resumeData，获取断点的NSURLSessionTask，调用resume恢复下载
//            self.resumeData = resumeData;
            //弹出提示框，如果需要重新下载，则调用[download taskwithResumeData]
        }
    } else {
       //下载完成处理
    }
    
    if (self.complete) {
        self.complete(error ? NO : YES, error ? nil : self.toPath, error);
    }
}

@end

下载调用

SYDownloadManager *manager = [[SYDownloadManager alloc] init];
    [manager downloadWithUrl:[NSURL URLWithString:url] toPath:toPath progress:^(float progress) {
         //other things
    } complete:^(BOOL success, NSString * _Nullable filePath, NSError * _Nullable error) {
        if (self.completeCallback) {
            NSDictionary *dic = error ? @{
                @"code" : @(error.code),
                @"success" : @(success),
                @"errMsg" : error.userInfo.description ? error.userInfo.description : @""
            } : @{
                @"success" : @(success),
                @"filePath" : filePath,
            };

          //other things
        }
    }];