資料下載 - delegate 形式的非同步請求

標籤：非同步   delegate   資料   下載   ios開發   

下載資料可以使用同步請求，非同步請求

之前有講到NSString 、 NSData 類型的同步請求

有NSURLConnection 形式的同步請求

非同步請求有block 形式的非同步請求,我們需要建立一個隊列 在block 內部實現

但是我們最常用的是 delegate 形式的非同步請求

#import "ViewController.h"@interface ViewController ()<NSURLConnectionDataDelegate>@property(nonatomic,weak)IBOutlet UIButton *button;@property(nonatomic,weak)IBOutlet UIImageView *imageView;@property(nonatomic,weak)IBOutlet UIProgressView *progressView;@property(nonatomic,retain)NSString *myURLStr;@property(nonatomic,retain)NSMutableData *result;@property(nonatomic,assign)float totalSize;@end@implementation ViewController//懶載入-(NSMutableData *)result{    if(_result == nil)    {        //_result = [[NSMutableData alloc]init];        _result = [NSMutableData data];    }    return _result;}- (void)viewDidLoad {    [super viewDidLoad];    // Do any additional setup after loading the view, typically from a nib.}-(IBAction)downloadBegin:(id)sender{    self.myURLStr = @"http://farm3.staticflickr.com/2846/9823925914_78cd653ac9_b_d.jpg";    //self.myURLStr = @"http://photo.candou.com/i/114/826ea823e8ffe792a6fda9e126f6c404";        //[self syncDownloadWithConnection];    //[self asyncDownloadWithBlock];    [self asyncDownloadWithDelegate];}//串連有相應，開始下載-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response{    [UIApplication sharedApplication].networkActivityIndicatorVisible = YES;        self.progressView.hidden = NO;    //擷取資料的總長度    self.totalSize = response.expectedContentLength;        NSLog(@"%@",NSStringFromSelector(_cmd));}//調用表示正在接受資料 根據大小反覆不間斷接受-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{    [self.result appendData:data];        float pv = self.result.length /self.totalSize;        self.progressView.progress = pv;        NSLog(@"下載進度%f",pv);    NSLog(@"%@",NSStringFromSelector(_cmd));    }//調用證明下載完畢-(void)connectionDidFinishLoading:(NSURLConnection *)connection{    [UIApplication sharedApplication].networkActivityIndicatorVisible = NO;        self.progressView.hidden = YES;        self.imageView.image = [UIImage imageWithData:self.result];    NSLog(@"%@",NSStringFromSelector(_cmd));}//串連發生錯誤 下載失敗//1.斷網了//2.網址出錯了-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error{    [UIApplication sharedApplication].networkActivityIndicatorVisible = NO;        self.progressView.hidden = YES;        NSLog(@"%@",NSStringFromSelector(_cmd));    NSLog(@"下載失敗");}#pragma mark -NSURLConnection非同步請求-//Delegate 形式的非同步請求-(void)asyncDownloadWithDelegate{    NSURL *url = [NSURL URLWithString:self.myURLStr];        NSURLRequest *request = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestReloadIgnoringCacheData timeoutInterval:10];        self.result.length = 0;        [NSURLConnection connectionWithRequest:request delegate:self];        }

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資料下載 - delegate 形式的非同步請求