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
