iOS断点续传

说明:本文介绍大文件的断点下载,并没有讲述多线程断点下载,项目中使用了苹果自带的类。

实现思路：下载开始，创建一个和要下载的文件大小相同的文件（如果要下载的文件为100M，那么就在沙盒中创建一个100M的文件，然后每次从服务器下载的文件,依次写入创建好的文件中）。

这里贴上封装的进度条的代码 DACircularProgressView.h

#import <UIKit/UIKit.h>

@interface DACircularProgressView : UIView

@property(nonatomic, strong) UIColor *trackTintColor;
@property(nonatomic, strong) UIColor *progressTintColor;
@property (nonatomic) float progress;

@end

DACircularProgressView.m

#import "DACircularProgressView.h"

#define DEGREES_2_RADIANS(x) (0.0174532925 * (x))

@implementation DACircularProgressView

@synthesize trackTintColor = _trackTintColor;
@synthesize progressTintColor =_progressTintColor;
@synthesize progress = _progress;

- (id)init
{
    self = [super initWithFrame:CGRectMake(0.0f, 0.0f, 40.0f, 40.0f)];
    if (self)
    {
        self.backgroundColor = [UIColor clearColor];
    }
    return self;
}

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self)
    {
        self.backgroundColor = [UIColor clearColor];
    }
    return self;
}

- (id)initWithCoder:(NSCoder *)aDecoder
{
    self = [super initWithCoder:aDecoder];
    if (self)
    {
        self.backgroundColor = [UIColor clearColor];
    }
    return self;
}

- (void)drawRect:(CGRect)rect
{    
    CGPoint centerPoint = CGPointMake(rect.size.height / 2, rect.size.width / 2);
    CGFloat radius = MIN(rect.size.height, rect.size.width) / 2;
    
    CGFloat pathWidth = radius * 0.3f;
    
    CGFloat radians = DEGREES_2_RADIANS((self.progress*359.9)-90);
    CGFloat xOffset = radius*(1 + 0.85*cosf(radians));
    CGFloat yOffset = radius*(1 + 0.85*sinf(radians));
    CGPoint endPoint = CGPointMake(xOffset, yOffset);
    
    CGContextRef context = UIGraphicsGetCurrentContext();
    
    [self.trackTintColor setFill];
    CGMutablePathRef trackPath = CGPathCreateMutable();
    CGPathMoveToPoint(trackPath, NULL, centerPoint.x, centerPoint.y);
    CGPathAddArc(trackPath, NULL, centerPoint.x, centerPoint.y, radius, DEGREES_2_RADIANS(270), DEGREES_2_RADIANS(-90), NO);
    CGPathCloseSubpath(trackPath);
    CGContextAddPath(context, trackPath);
    CGContextFillPath(context);
    CGPathRelease(trackPath);
    
    [self.progressTintColor setFill];
    CGMutablePathRef progressPath = CGPathCreateMutable();
    CGPathMoveToPoint(progressPath, NULL, centerPoint.x, centerPoint.y);
    CGPathAddArc(progressPath, NULL, centerPoint.x, centerPoint.y, radius, DEGREES_2_RADIANS(270), radians, NO);
    CGPathCloseSubpath(progressPath);
    CGContextAddPath(context, progressPath);
    CGContextFillPath(context);
    CGPathRelease(progressPath);
    
    CGContextAddEllipseInRect(context, CGRectMake(centerPoint.x - pathWidth/2, 0, pathWidth, pathWidth));
    CGContextFillPath(context);
    
    CGContextAddEllipseInRect(context, CGRectMake(endPoint.x - pathWidth/2, endPoint.y - pathWidth/2, pathWidth, pathWidth));
    CGContextFillPath(context);
    
    CGContextSetBlendMode(context, kCGBlendModeClear);;
    CGFloat innerRadius = radius * 0.7;
    CGPoint newCenterPoint = CGPointMake(centerPoint.x - innerRadius, centerPoint.y - innerRadius);    
    CGContextAddEllipseInRect(context, CGRectMake(newCenterPoint.x, newCenterPoint.y, innerRadius*2, innerRadius*2));
    CGContextFillPath(context);
}

#pragma mark - Property Methods

- (UIColor *)trackTintColor
{
    if (!_trackTintColor)
    {
        _trackTintColor = [UIColor colorWithRed:1.0f green:1.0f blue:1.0f alpha:0.3f];
    }
    return _trackTintColor;
}

- (UIColor *)progressTintColor
{
    if (!_progressTintColor)
    {
        _progressTintColor = [UIColor whiteColor];
    }
    return _progressTintColor;
}

- (void)setProgress:(float)progress
{
    _progress = progress;
    [self setNeedsDisplay];
}

@end

控制器中的代码:

#import "ViewController.h"
#import "DACircularProgressView.h"

@interface ViewController ()<NSURLConnectionDataDelegate>

/**
 *  用来写数据的文件句柄对象
 */
@property (nonatomic, strong) NSFileHandle *writeHandle;
/**
 *  文件的总大小
 */
@property (nonatomic, assign) long long totalLength;
/**
 *  当前已经写入的文件大小
 */
@property (nonatomic, assign) long long currentLength;

/**
 *  连接对象
 */
@property (nonatomic, strong) NSURLConnection *conn;

/**
 *  自定义的进度条
 */
@property (nonatomic, weak) DACircularProgressView *circleView;

@end

创建一个显示进度的进度条

- (void)viewDidLoad
{
    NSLog(@"%@",NSHomeDirectory());
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    DACircularProgressView *circleView = [[DACircularProgressView alloc] init];
    circleView.frame = CGRectMake(100, 50, 100, 100);
    circleView.progressTintColor = [UIColor redColor];
    circleView.trackTintColor = [UIColor greenColor];
    circleView.progress = 0.0000001;
    [self.view addSubview:circleView];
    self.circleView = circleView;
}

#pragma mark - NSURLConnectionDataDelegate代理方法
/**
 *  请求失败时调用（请求超时、网络异常）
 *
 *  @param error      错误原因
 */
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    NSLog(@"didFailWithError");
}

/**
 *  1.接收到服务器的响应就会调用
 *
 *  @param response   响应
 */
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    if (self.currentLength) return;
    
    // 文件路径
    NSString *caches = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject];
    NSString *filepath = [caches stringByAppendingPathComponent:@"videosssssss.zip"];
    
    // 创建一个空的文件 到 沙盒中
    NSFileManager *mgr = [NSFileManager defaultManager];
    [mgr createFileAtPath:filepath contents:nil attributes:nil];
    
    // 创建一个用来写数据的文件句柄
    self.writeHandle = [NSFileHandle fileHandleForWritingAtPath:filepath];
    
    // 获得文件的总大小
    self.totalLength = response.expectedContentLength;
}
   /**
 *  2.当接收到服务器返回的实体数据时调用（具体内容，这个方法可能会被调用多次）
 *
 *  @param data       这次返回的数据
 */
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    // 移动到文件的最后面
    [self.writeHandle seekToEndOfFile];
    
    // 将数据写入沙盒
    [self.writeHandle writeData:data];
    
    // 累计文件的长度
    self.currentLength += data.length;
    
    self.circleView.progress = (double)self.currentLength/ self.totalLength;
    NSLog(@"%lld",self.currentLength);
}

/**
 *  3.加载完毕后调用（服务器的数据已经完全返回后）
 */
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    self.currentLength = 0;
    self.totalLength = 0;
    
    // 关闭文件
    [self.writeHandle closeFile];
    self.writeHandle = nil;
//    NSLog(@"%@")
}

- (IBAction)download:(UIButton *)sender {
    // 状态取反
    sender.selected = !sender.isSelected;
    
    // 断点续传
    // 断点下载
    
    if (sender.selected) { // 继续（开始）下载
        // 1.URL
        NSURL *url = [NSURL URLWithString:@"http://m1.music.126.net/xN7iliJNnWqt7DGdznES-A==/7936274929998920.mp3"];
        
        // 2.请求
        NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
        
        // 设置请求头
        NSString *range = [NSString stringWithFormat:@"byte=%lld-", self.currentLength];
        [request setValue:range forHTTPHeaderField:@"Range"];
        
        // 3.下载(创建完conn对象后，会自动发起一个异步请求)
        self.conn = [NSURLConnection connectionWithRequest:request delegate:self];
    } else { // 暂停
        [self.conn cancel];
        self.conn = nil;
    }
}

@end