原文网址：http://blog.csdn.net/m_changgong/article/details/8238093 作者：张燕广
实现的功能：1）演示多线程NSOperation&NSOperationQueue开发；2）子线程中执行下载图片工作，图片下载完成前显示等待框和下载进度条；
关键词：多线程 NSOperation NSOperationQueue 等待框
1、新建视图控制器ViewController（不带xib），作为根视图控制器，通过ViewController的-(void)loadView方法构建UI。
2、新建继承自NSOperation且实现协议NSURLConnectionDelegate的类DownLoadImageTask，DownLoadImageTask.h如下：
#import <Foundation/Foundation.h>
@protocol DownLoadImageDelegate;
@interface DownLoadImageTask : NSOperation<NSURLConnectionDelegate>{
int operationId;
long long totalLength;
BOOL done;
}
@property int operationId;
@property(nonatomic,assign) id<DownLoadImageDelegate>downloadImageDelegate;
@property(nonatomic,retain) NSMutableData *buffer;
@property(nonatomic,retain) NSURLRequest *request;
@property(nonatomic,retain) NSURLConnection *connection;
- (id)initWithURLString:(NSString *)url;
@end
@protocol DownLoadImageDelegate
//图片下载完成的委托
-(void)imageDownLoadFinished:(UIImage *)img;
//更新图片下载进度条的值
-(void)updateDownProgress:(double) value;
@end
DownLoadImageTask.m如下：
#import "DownLoadImageTask.h"
@implementation DownLoadImageTask
@synthesize operationId;
@synthesize downloadImageDelegate;
@synthesize buffer;
@synthesize request;
@synthesize connection;
- (id)initWithURLString:(NSString *)url{
NSLog(@"url=%@",url);
self = [super init];
if(self){
request = [NSURLRequest requestWithURL:[NSURL URLWithString:url]];
buffer = [NSMutableData data];
}
return self;
}
//主要处理方法
-(void)start{ //或者main
NSLog(@"DownLoadImageTask-start");
if(![self isCancelled]){
//暂停一下
[NSThread sleepForTimeInterval:1];
//设置connection及其代理
connection = [[NSURLConnection alloc]initWithRequest:request delegate:self];
if(connection!=nil){
while(!done){
[[NSRunLoop currentRunLoop]runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];
}
}
}
}
-(void)httpConnectEndWithError{
//[self hiddenWaiting];
NSLog(@"httpConnectEndWithError");
}
-(void)dealloc{
buffer = nil;
connection = nil;
request = nil;
downloadImageDelegate = nil;
}
#pragma NSURLConnection delegate methods
//不执行缓存
-(NSCachedURLResponse *)connection:(NSURLConnection *)connection willCacheResponse:(NSCachedURLResponse *)cachedResponse{
return nil;
}
//连接发生错误
-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error{
[self performSelectorOnMainThread:@selector(httpConnectEndWithError) withObject:self waitUntilDone:NO];
[buffer setLength:0];
}
//收到响应
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response{
NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *)response;
if(httpResponse && [httpResponse respondsToSelector:@selector(allHeaderFields)]){
NSDictionary *httpResponseHeaderFields = [httpResponse allHeaderFields];
totalLength = [[httpResponseHeaderFields objectForKey:@"Content-Length"] longLongValue];
NSLog(@"totalLength is %lld",totalLength);
}
}
//接收数据
-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{
//NSLog(@"didReceiveData...");
[buffer appendData:data];
double progressValue = totalLength==0?0:((double)([buffer length])/(double)totalLength);
//更新进度条值
[downloadImageDelegate updateDownProgress:progressValue];
}
//下载完毕
-(void)connectionDidFinishLoading:(NSURLConnection *)connection{
done = YES;
UIImage *img = [[UIImage alloc] initWithData:buffer];
[downloadImageDelegate imageDownLoadFinished:img];
}
-(BOOL)isConcurrent {
//返回yes表示支持异步调用，否则为支持同步调用
return YES;
}
- (BOOL)isExecuting{
return connection == nil;
}
- (BOOL)isFinished{
return connection == nil;
}
@end
DownLoadImageTask中定义了协议DownLoadImageDelegate，ViewController需要实现协议DownLoadImageDelegate；DownLoadImageTask下载工作完成后，会回调ViewController实现的DownLoadImageDelegate协议中的方法。
2、ViewController.h如下：
#import <UIKit/UIKit.h>
#import "DownLoadImageTask.h"
@interface ViewController:UIViewController<DownLoadImageDelegate>{
}
@property(strong,nonatomic)NSOperationQueue *queue;
@property(strong,nonatomic)UIImageView *appImgView;
@end
ViewController.m如下：
#import "ViewController.h"
#import "DownLoadImageTask.h"
@implementation ViewController
@synthesize queue;
@synthesize appImgView;
-(void)loadView{
//初始化视图
[self initViews];
//显示等待框
[self showWaiting];
NSString *url = @"http://hiphotos.baidu.com/newwen666666/pic/item/01ec7750863e49600cf3e3cc.jpg";
int index = 1;
DownLoadImageTask *task = [[DownLoadImageTask alloc]initWithURLString:url];
task.downloadImageDelegate = self;
task.operationId = index++;
queue = [[NSOperationQueue alloc]init];
[queue addOperation:task];
}
//初始化视图组件
-(void)initViews{
CGRect frame = [UIScreen mainScreen].applicationFrame;
UIView *appView = [[UIView alloc]initWithFrame:frame];
self.view = appView;
[self.view setBackgroundColor:[UIColor colorWithWhite:1.0 alpha:1.0]];
frame = CGRectMake(0, 0, frame.size.width, frame.size.height);
appImgView = [[UIImageView alloc]initWithFrame:frame];
[self.view addSubview:appImgView];
}
//展示等待框
-(void)showWaiting{
CGRect frame = CGRectMake(0, -20, 320, 480);
int x = frame.size.width;
int progressWidth = 150;
int progressHeight = 32;
frame = CGRectMake((x-progressWidth)/2, 100, progressWidth, progressHeight);
UIProgressView *progress = [[UIProgressView alloc]initWithProgressViewStyle:UIProgressViewStyleBar];
progress.frame = frame;
progress.progress = 0.0;
progress.backgroundColor = [UIColor whiteColor];
UILabel *showValue = [[UILabel alloc]init];
frame = showValue.frame;
frame.origin.x = CGRectGetMaxX(progress.frame)+10;
frame.origin.y = CGRectGetMinY(progress.frame);
frame.size.width = 45;
frame.size.height = 15;
showValue.frame = frame;
showValue.backgroundColor = [UIColor redColor];
showValue.text = @"0.0";
int progressIndWidth = 32;
int progressIndHeight = 32;
frame = CGRectMake((x-progressIndWidth)/2, 100+32, progressIndWidth, progressIndHeight);
UIActivityIndicatorView *progressInd = [[UIActivityIndicatorView alloc]initWithFrame:frame];
[progressInd startAnimating];
progressInd.activityIndicatorViewStyle = UIActivityIndicatorViewStyleWhiteLarge;
frame = CGRectMake((x-70)/2, 100+32+32, 80, 20);
UILabel *waitinglabel = [[UILabel alloc]initWithFrame:frame];
waitinglabel.text = @"正在下载应用程序图片...";
waitinglabel.textColor = [UIColor redColor];
waitinglabel.font = [UIFont systemFontOfSize:15];
waitinglabel.backgroundColor = [UIColor clearColor];
frame = CGRectMake(0, -20, 320, 480);
UIView *theView = [[UIView alloc]initWithFrame:frame];
theView.backgroundColor = [UIColor blackColor];
theView.alpha = 0.7;
[progress setTag:100];
[theView addSubview:progress];
[showValue setTag:101];
[theView addSubview:showValue];
[theView addSubview:progressInd];
[theView addSubview:waitinglabel];
[theView setTag:110];
[self.view addSubview:theView];
}
//隐藏等待框
-(void)hiddenWaiting{
[[self.view viewWithTag:110]removeFromSuperview];
}
- (void)viewDidUnload
{
[super viewDidUnload];
// Release any retained subviews of the main view.
}
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
}
#pragma mark DownLoadImageDelegate methods
//展示下载完毕的图片
-(void)imageDownLoadFinished:(UIImage *)img{
//退出等待框
[self hiddenWaiting];
[appImgView setImage:img];
}
//更新进度条的值
-(void)updateDownProgress:(double) value{
UIProgressView *progresss = (UIProgressView *)[self.view viewWithTag:100];
UILabel *showValue = (UILabel*)[self.view viewWithTag:101];
progresss.progress = value;
showValue.text = [NSString stringWithFormat:@"%.1f%",(double)(value*100)];
}
@end
3、效果如下：
