网络编程---将网络上的大文件下载到本地，并打印其进度。
点击“开始传输”按钮，将网络上的大文件先下载下来，下载完成后，保存到本地。
UI效果图如下：
具体代码如下：
// ViewController.m
// 0611---数据请求+滚动条
#import "ViewController.h"
unsigned
long tempLength;
@interface
ViewController () <NSURLConnectionDataDelegate>
{
NSMutableData * resultData;
UISlider * _slider;
}
@end
@implementation ViewController
- (void)viewDidLoad {
[super
viewDidLoad];
[self
_loadView];
}
- (void) _loadView
{
self.view.backgroundColor=[UIColor
colorWithRed:0
green:1
blue:1
alpha:0.7];
UISlider * slider=[[UISlider
alloc]initWithFrame:CGRectMake(0,
200, self.view.frame.size.width,
40)];
slider.backgroundColor=[UIColor
colorWithRed:0.1
green:0.1
blue:0.7
alpha:0.2];
slider.minimumValue=0;
//设置最小值
slider.maximumValue=1;
//设置最大值
slider.value=0;
//设置起始值
slider.enabled=YES;
_slider=slider;
[self.view
addSubview:slider];
// NSLog(@"%f",self.view.frame.size.width); 375
// NSLog(@"%f",self.view.frame.size.height); 667
UIButton * button=[[UIButton
alloc]initWithFrame:CGRectMake(0,
0, 120,
50)];
button.center=self.view.center;
[button setTitle:@"开始传输"
forState:UIControlStateNormal];
[button setTitleColor:[UIColor
redColor] forState:UIControlStateNormal];
button.backgroundColor=[UIColor
colorWithRed:0.1
green:0.1
blue:0.1
alpha:0.4];
[button addTarget:self
action:@selector(startTransition)
forControlEvents:UIControlEventTouchUpInside];
[self.view
addSubview: button];
}
- (void)startTransition
{
NSLog(@"点击了按钮~");
//通过URL建立请求对象
NSURL * url=[NSURL
URLWithString:@"http://192.168.2.106/hahaha.zip"];
NSURLRequest * request=[NSURLRequest
requestWithURL:url];
//创建NSURLConnection
对象用来连接服务器并且发送请求
NSURLConnection * conn=[[NSURLConnection
alloc]initWithRequest:request
delegate:self];
[conn
start];
}
#pragma mark - 代理方法
//接受到响应
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse
*)response
{
NSLog(@"-------%lu",(unsigned
long)response.expectedContentLength);
tempLength=(unsigned
long)response.expectedContentLength;
resultData =[NSMutableData
data];
}
//接收到数据
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData
*)data
{
[resultData
appendData:data];
_slider.value=(float)resultData.length/(float)tempLength;
NSLog(@"%lu ***** %f",(unsigned
long)resultData.length,_slider.value);
}
//结束下载
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
NSLog(@"下载结束，保存到本地文件");
//创建一个文件
NSFileManager * manager=[NSFileManager
defaultManager];
//用path保存路径
NSString * path = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory,
NSUserDomainMask, YES)
firstObject];
path=[path stringByAppendingPathComponent:@"hahaha1.zip"];
NSLog(@"%@", path);
//在路径下创建文档并将数据写入文档
[manager createFileAtPath:path
contents:resultData
attributes:nil];
}
//请求失败
- (void) connection:(NSURLConnection *)connection didFailWithError:(NSError
*)error
{
NSLog(@"didFailWithError");
}
@end
需要注意的是，slider的值是两个数之比，要保证两个数是float类型。