ios大文件下载封装

#import <Foundation/Foundation.h>

@interface HMFileDownloader : NSObject
/**
 * 所需要下载文件的远程URL(连接服务器的路径)
 */
@property (nonatomic, copy) NSString *url;
/**
 * 文件的存储路径(文件下载到什么地方)
 */
@property (nonatomic, copy) NSString *destPath;

/**
 * 是否正在下载(有没有在下载, 只有下载器内部才知道)
 */
@property (nonatomic, readonly, getter = isDownloading) BOOL downloading;

/**
 * 用来监听下载进度
 */
@property (nonatomic, copy) void (^progressHandler)(double progress);
/**
 * 用来监听下载完毕
 */
@property (nonatomic, copy) void (^completionHandler)();
/**
 * 用来监听下载失败
 */
@property (nonatomic, copy) void (^failureHandler)(NSError *error);

/**
 * 开始(恢复)下载
 */
- (void)start;

/**
 * 暂停下载
 */
- (void)pause;

@end



#import "HMFileDownloader.h"

@interface HMFileDownloader() <NSURLConnectionDataDelegate>
/**
 * 连接对象
 */
@property (nonatomic, strong) NSURLConnection *conn;

/**
 *  写数据的文件句柄
 */
@property (nonatomic, strong) NSFileHandle *writeHandle;
/**
 *  当前已下载数据的长度
 */
@property (nonatomic, assign) long long currentLength;
/**
 *  完整文件的总长度
 */
@property (nonatomic, assign) long long totalLength;
@end

@implementation HMFileDownloader

/**
 * 开始(恢复)下载
 */
- (void)start
{
    NSURL *url = [NSURL URLWithString:self.url];
    // 默认就是GET请求
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
    // 设置请求头信息
    NSString *value = [NSString stringWithFormat:@"bytes=%lld-", self.currentLength];
    [request setValue:value forHTTPHeaderField:@"Range"];
    self.conn = [NSURLConnection connectionWithRequest:request delegate:self];
    
    _downloading = YES;
}

/**
 * 暂停下载
 */
- (void)pause
{
    [self.conn cancel];
    self.conn = nil;
    
    _downloading = NO;
}

#pragma mark - NSURLConnectionDataDelegate 代理方法
/**
 *  1. 当接受到服务器的响应(连通了服务器)就会调用
 */
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
#warning 一定要判断
    if (self.totalLength) return;
    
    // 1.创建一个空的文件到沙盒中
    NSFileManager *mgr = [NSFileManager defaultManager];
    // 刚创建完毕的大小是0字节
    [mgr createFileAtPath:self.destPath contents:nil attributes:nil];
    
    // 2.创建写数据的文件句柄
    self.writeHandle = [NSFileHandle fileHandleForWritingAtPath:self.destPath];
    
    // 3.获得完整文件的长度
    self.totalLength = response.expectedContentLength;
}

/**
 *  2. 当接受到服务器的数据就会调用(可能会被调用多次, 每次调用只会传递部分数据)
 */
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    // 累加长度
    self.currentLength += data.length;
    
    // 显示进度
    double progress = (double)self.currentLength / self.totalLength;
    if (self.progressHandler) { // 传递进度值给block
        self.progressHandler(progress);
    }
    
    // 移动到文件的尾部
    [self.writeHandle seekToEndOfFile];
    // 从当前移动的位置(文件尾部)开始写入数据
    [self.writeHandle writeData:data];
}

/**
 *  3. 当服务器的数据接受完毕后就会调用
 */
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    // 清空属性值
    self.currentLength = 0;
    self.totalLength = 0;
    
    if (self.currentLength == self.totalLength) {
        // 关闭连接(不再输入数据到文件中)
        [self.writeHandle closeFile];
        self.writeHandle = nil;
    }
    
    if (self.completionHandler) {
        self.completionHandler();
    }
}

/**
 *  请求错误(失败)的时候调用(请求超时\断网\没有网, 一般指客户端错误)
 */
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    if (self.failureHandler) {
        self.failureHandler(error);
    }
}

@end

 

#import "HMViewController.h"
#import "HMFileDownloader.h"

@interface HMViewController ()
@property (weak, nonatomic) IBOutlet UIProgressView *progressView;
@property (nonatomic, strong) HMFileDownloader *fileDownloader;

- (IBAction)start:(UIButton *)button;
@end

@implementation HMViewController

- (HMFileDownloader *)fileDownloader
{
    if (!_fileDownloader) {
        _fileDownloader = [[HMFileDownloader alloc] init];
        // 需要下载的文件远程URL
        _fileDownloader.url = @"http://192.168.1.200:8080/MJServer/resources/jre.zip";
        // 文件保存到什么地方
        NSString *caches = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject];
        NSString *filepath = [caches stringByAppendingPathComponent:@"jre.zip"];
        _fileDownloader.destPath = filepath;
//        typeof(10) a = 20; // int a = 20;
        
        __weak typeof(self) vc = self;
        _fileDownloader.progressHandler = ^(double progress) {
            vc.progressView.progress = progress;
        };
        
        _fileDownloader.completionHandler = ^{
            NSLog(@"------下载完毕");
        };
        
        _fileDownloader.failureHandler = ^(NSError *error){
        
        };
    }
    return _fileDownloader;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    
}

// 按钮文字: "开始", "暂停"
- (IBAction)start:(UIButton *)button { // self.currentLength == 200
    if (self.fileDownloader.isDownloading) { // 暂停下载
        [self.fileDownloader pause];
        
        [button setTitle:@"恢复" forState:UIControlStateNormal];
    } else { // 开始下载
        [self.fileDownloader start];
        
        [button setTitle:@"暂停" forState:UIControlStateNormal];
    }
}

@end