4_1网络学习第一天后感--网络数据下载
1、网络数据下载包括同步下载和异步下载,一般是使用异步下载,异步下载可以利用NSURLConnection这个类。
2、有关数据格式,有JSON格式(多数)、XML格式。JSON格式如下:
{} 代表字典,[] 代表数组 ,“” 代表字符串 , 100 代表NSNumber
3、分析网络接口
如:@"http://iappfree.candou.com:8080/free/applications/limited?currency=rmb&page=1&category_id="
http:// (地址使用协议) iappfree.candou.com (主机地址) 8080 (主机端口)
free/applications/limited(网络程序文件路径) ?currency=rmb&page=1&category_id= (程序参数)
4、NSURLConnection的同步下载代码:
-(void)testNSURLConnectionSyncDownloadData
{
//限免页面接口
NSString *urlString=@"http://iappfree.candou.com:8080/free/applications/limited?currency=rmb&page=1&category_id=";
//发送同步URL请求
//NSURLRequest URL请求对象
NSURL *url=[NSURL URLWithString:urlString];
NSURLRequest *request=[NSURLRequest requestWithURL:url];
NSError *error=nil;
NSData *data=[NSURLConnection sendSynchronousRequest:request returningResponse:nil error:&error];
if (error==nil) {
NSString *str=[[NSString alloc]initWithData:data encoding:NSUTF8StringEncoding];
NSLog(@"str = %@",str);
}
else {
NSLog(@"下载失败");
}
}
5、NSURLConnection的异步下载代码:
-(void)testNSURLConnectionAsyncDownloadData { _data=[[NSMutableData alloc]init]; //限免页面接口 NSString *urlString=@"http://iappfree.candou.com:8080/free/applications/limited?currency=rmb&page=1&category_id="; //发起一个异步URL请求 //异步:执行了方法之后,开始下载 _connection=[[NSURLConnection alloc]initWithRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:urlString]] delegate:self startImmediately:YES]; } //下面是<NSURLConnectionDataDelegate>代理方法 //接收到服务器响应执行 -(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response { NSLog(@"接收到服务器响应执行"); } //接收到数据的时候执行 //注意:当数据比较大,可能会多次执行 -(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data { [_data appendData:data]; } //当数据下载完成了 -(void)connectionDidFinishLoading:(NSURLConnection *)connection { // NSLog(@"str =%@",[[NSString alloc]initWithData:_data encoding:NSUTF8StringEncoding]); //解析JSON (把JSON转化为NSArray或NSDictionary NSDictionary *dict=[NSJSONSerialization JSONObjectWithData:_data options:NSJSONReadingMutableContainers error:nil]; NSArray *appList=dict[@"applications"]; for (NSDictionary *appDict in appList) { NSLog(@"name = %@",appDict[@"name"]); } } //下载失败 -(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error { NSLog(@"error =%@",error); }
6、封装NSURLConnection(重点)
先创建一个NSObject类,
#import <Foundation/Foundation.h>
@interface ZJHttpRequset : NSObject
//data用来保存下载的数据
@property (nonatomic,copy) NSMutableData *data;
//传人一个网站,下载完成之后,执行target中action的方法
-(void)requestWithUrl:(NSString *)url target:(id)target action:(SEL)action;
@end
#import "ZJHttpRequset.h"
#import "AppModel.h"
//消除performSelector的警告
#pragma clang diagnostic ignored "-Warc-performSelector-leaks"
//类扩展,有些实例变量内部使用,不想放在头文件,就可以放在类扩展里面。
@interface ZJHttpRequset ()<NSURLConnectionDataDelegate>
{
NSURLConnection *_connection;
//用来保存存进来的url target action
NSString *_url;
id _target;
SEL _action;
}
@end
@implementation ZJHttpRequset
-(void)requestWithUrl:(NSString *)url target:(id)target action:(SEL)action
{
//保存存进来的变量
_url=url;
_target=target;
_action=action;
//记住要初始化data!!!
_data=[[NSMutableData alloc]init];
//发起异步URL请求
_connection=[[NSURLConnection alloc]initWithRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:url]] delegate:self startImmediately:YES];
}
//NSURLConnection代理方法
//接收数据
-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
[_data appendData:data];
}
//下载完成了,执行方法
-(void)connectionDidFinishLoading:(NSURLConnection *)connection
{
if (_target&&[_target respondsToSelector:_action]) {
[_target performSelector:_action withObject:self];
}
//这里面的Object就是这个类本身,目的是把接收到的data传递
}
再传入网络接口,利用这个封装好的NSURLConnection类接收
@implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
//数据接口
NSString *urlString=@"http://iappfree.candou.com:8080/free/applications/limited?currency=rmb&page=1&category_id=";
//初始化数组(tabelView的数据总数组)
_dataArray =[NSMutableArray array];
//初始化自封装好的NSURLConnection类
_request=[[ZJHttpRequset alloc]init];
[_request requestWithUrl:urlString target:self action:@selector(dealDownloadFinish:)];
//创建表视图
[self createTableView];
}
//接收完成之后会触发的方法(在自封装的URL类中 使用PerformSelector)
-(void)dealDownloadFinish:(ZJHttpRequset *)request
{
//JSON解析,(获得的是数组还是字典,需要在JASON软件中查看)
NSDictionary *dict=[NSJSONSerialization JSONObjectWithData:request.data
options:NSJSONReadingMutableContainers error:nil];
NSArray *appList=dict[@"applications"];
//利用数据模型保存网络接口下的数据,然后把模型添加到tableView总数组
for (NSDictionary *appDict in appList) {
AppModel *model=[[AppModel alloc]initWithDict:appDict];
[_dataArray addObject:model];
}
//下载完数据,更新了总数组,一定要刷新tableview!!!
[_tableView reloadData];
}
7、作业
scrollView滑动
//第一步:初始化,从网络接口下载数据
-(void)createScrollView
{
_allData1=[NSMutableArray array];
//陈奕迅网络接口
NSString *urlString=@"http://mapi.damai.cn/hot201303/nindex.aspx?cityid=0&source=10099&version=30602";
_request1 =[[LCHttpRequest alloc]init];
[_request1 requestUrl:urlString withTarget:self andAction:@selector(scrollViewDownload:)];
}
//第二步:下载完成后触发的方法,把下载好的data 存入总数组
-(void)scrollViewDownload:(LCHttpRequest *)request
{
NSArray *arr=[NSJSONSerialization JSONObjectWithData:request.data options:NSJSONReadingMutableContainers error:nil];
for (NSDictionary *dict in arr) {
NSString *str=dict[@"Pic"];
[_allData1 addObject:str];
}
[self loadImage];
}
//第三步:根据下载的总数组,改变ScrollView的contenSize 同时设置其imageView
-(void)loadImage
{
_scrollView.contentSize=CGSizeMake(320*_allData1.count, 0);
for (int i=0; i<_allData1.count; i++) {
UIImageView *imageView=[[UIImageView alloc]initWithFrame:CGRectMake(320*i, 0, 320, 165)];
NSString *str= _allData1[i];
[imageView setImageWithURL:[NSURL URLWithString:str]];
[_scrollView addSubview:imageView];
}
//设置pageControl
_pageControl.numberOfPages=_allData1.count;
_pageControl.enabled=NO;
[self.view bringSubviewToFront:_pageControl];
_pageControl.pageIndicatorTintColor=[UIColor redColor];
//启动定时器,让scroView滑动
[NSTimer scheduledTimerWithTimeInterval:3.0 target:self selector:@selector(scrollViewMove) userInfo:nil repeats:YES];
}
//定时器触发的方法
-(void)scrollViewMove
{
CGPoint pp=_scrollView.contentOffset;
if (pp.x==320*(_allData1.count-1)) {
pp.x=0;
_scrollView.contentOffset=pp;
}
else{
pp.x+=320;
[UIView animateWithDuration:2.0 animations:^{
_scrollView.contentOffset=pp;
}];
}
}
//<UIScrllViewDelegate> 代理方法让pageControl跟着移动
-(void)scrollViewDidScroll:(UIScrollView *)scrollView
{
int page =scrollView.contentOffset.x/320;
_pageControl.currentPage=page;
}