大文件下载，我们不能像下载小文件那样直接使用一个变量来接受，因为这样会加载内存。所以我们的解决思路应该是下载一点数据就向文件中写入一点。另外，在下载过程中暂停下载后，如何做到从某一地方开始继续下载，这时就需要我们在发请求时，将下载的开始信息包装到请求头中。
方式一：使用NSFileHandle创建文件句柄来写数据
#import "ViewController.h"
@interface ViewController ()<NSURLConnectionDataDelegate>
@property (weak, nonatomic) IBOutlet UIProgressView *progressView;
@property (nonatomic, assign) NSInteger totalSize;
@property (nonatomic, assign) NSInteger currentSize;
/** 文件句柄*/
@property (nonatomic, strong)NSFileHandle *handle;
/** 沙盒路径 */
@property (nonatomic, strong) NSString *fullPath;
/** 连接对象 */
@property (nonatomic, strong) NSURLConnection *connect;
@end
@implementation ViewController
- (IBAction)startBtnClick:(id)sender {
[self download];
}
- (IBAction)cancelBtnClick:(id)sender {
[self.connect cancel];
}
- (IBAction)goOnBtnClick:(id)sender {
[self download];
}
//内存飙升
-(void)download
{
//1.url
NSURL *url = [NSURL URLWithString:@"http://www.33lc.com/article/UploadPic/2012-10/2012102514201759594.jpg"];
//2.创建请求对象
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
//设置请求头信息,告诉服务器值请求一部分数据range
/*
bytes=0-100
bytes=-100
bytes=0- 请求100之后的所有数据
*/
NSString *range = [NSString stringWithFormat:@"bytes=%zd-",self.currentSize];
[request setValue:range forHTTPHeaderField:@"Range"];
NSLog(@"+++++++%@",range);
//3.发送请求
NSURLConnection *connect = [[NSURLConnection alloc]initWithRequest:request delegate:self];
self.connect = connect;
}
#pragma mark ----------------------
#pragma mark NSURLConnectionDataDelegate
-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
NSLog(@"didReceiveResponse");
//1.得到文件的总大小(本次请求的文件数据的总大小 != 文件的总大小)
// self.totalSize = response.expectedContentLength + self.currentSize;
if (self.currentSize >0) {
return;
}
self.totalSize = response.expectedContentLength;
//2.写数据到沙盒中
self.fullPath = [[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject]stringByAppendingPathComponent:response.suggestedFilename];
NSLog(@"%@",self.fullPath);
//3.创建一个空的文件
[[NSFileManager defaultManager] createFileAtPath:self.fullPath contents:nil attributes:nil];
//NSDictionary *dict = [[NSFileManager defaultManager]attributesOfItemAtPath:self.fullPath error:nil];
//4.创建文件句柄(指针)
self.handle = [NSFileHandle fileHandleForWritingAtPath:self.fullPath];
}
-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
//1.移动文件句柄到数据的末尾
[self.handle seekToEndOfFile];
//2.写数据
[self.handle writeData:data];
//3.获得进度
self.currentSize += data.length;
//进度=已经下载/文件的总大小
NSLog(@"%f",1.0 * self.currentSize/self.totalSize);
self.progressView.progress = 1.0 * self.currentSize/self.totalSize;
//NSLog(@"%@",self.fullPath);
}
-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
}
-(void)connectionDidFinishLoading:(NSURLConnection *)connection
{
//1.关闭文件句柄
[self.handle closeFile];
self.handle = nil;
NSLog(@"connectionDidFinishLoading");
NSLog(@"%@",self.fullPath);
}
@end
方式二：使用NSOutputStream输出流来写数据
#import "ViewController.h"
@interface ViewController ()<NSURLConnectionDataDelegate>
@property (weak, nonatomic) IBOutlet UIProgressView *progressView;
@property (nonatomic, assign) NSInteger totalSize;
@property (nonatomic, assign) NSInteger currentSize;
/** 沙盒路径 */
@property (nonatomic, strong) NSString *fullPath;
/** 连接对象 */
@property (nonatomic, strong) NSURLConnection *connect;
/** 输出流*/
@property (nonatomic, strong) NSOutputStream *stream;
@end
@implementation ViewController
- (IBAction)startBtnClick:(id)sender {
[self download];
}
- (IBAction)cancelBtnClick:(id)sender {
[self.connect cancel];
}
- (IBAction)goOnBtnClick:(id)sender {
[self download];
}
//内存飙升
-(void)download
{
//1.url
// NSURL *url = [NSURL URLWithString:@"http://imgsrc.baidu.com/forum/w%3D580/sign=54a8cc6f728b4710ce2ffdc4f3cec3b2/d143ad4bd11373f06c0b5bd1a40f4bfbfbed0443.jpg"];
NSURL *url = [NSURL URLWithString:@"http://www.33lc.com/article/UploadPic/2012-10/2012102514201759594.jpg"];
//2.创建请求对象
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
//设置请求头信息,告诉服务器值请求一部分数据range
/*
bytes=0-100
bytes=-100
bytes=0- 请求100之后的所有数据
*/
NSString *range = [NSString stringWithFormat:@"bytes=%zd-",self.currentSize];
[request setValue:range forHTTPHeaderField:@"Range"];
NSLog(@"+++++++%@",range);
//3.发送请求
NSURLConnection *connect = [[NSURLConnection alloc]initWithRequest:request delegate:self];
self.connect = connect;
}
#pragma mark ----------------------
#pragma mark NSURLConnectionDataDelegate
-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
NSLog(@"didReceiveResponse");
//1.得到文件的总大小(本次请求的文件数据的总大小 != 文件的总大小)
// self.totalSize = response.expectedContentLength + self.currentSize;
if (self.currentSize >0) {
return;
}
self.totalSize = response.expectedContentLength;
//2.写数据到沙盒中
self.fullPath = [[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject]stringByAppendingPathComponent:response.suggestedFilename];
NSLog(@"%@",self.fullPath);
//3.创建输出流
// NSOutputStream
// NSInputStream
/*
第一个参数:文件的路径
第二个参数:YES 追加
特点:如果该输出流指向的地址没有文件,那么会自动创建一个空的文件
*/
NSOutputStream *stream = [[NSOutputStream alloc]initToFileAtPath:self.fullPath append:YES];
//打开输出流
[stream open];
self.stream = stream;
}
-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
//写数据
[self.stream write:data.bytes maxLength:data.length];
//3.获得进度
self.currentSize += data.length;
//进度=已经下载/文件的总大小
NSLog(@"%f",1.0 * self.currentSize/self.totalSize);
self.progressView.progress = 1.0 * self.currentSize/self.totalSize;
//NSLog(@"%@",self.fullPath);
}
-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
}
-(void)connectionDidFinishLoading:(NSURLConnection *)connection
{
//关闭流
[self.stream close];
self.stream = nil;
NSLog(@"connectionDidFinishLoading");
NSLog(@"%@",self.fullPath);
}
@end
