iOS開發之非同步載入圖片

比較原始的方法：AsyncImageView.h:

#import <UIKit/UIKit.h> @interface AsyncImageView : UIView {     NSURLConnection* connection;     NSMutableData* data; } - (void)loadImageFromURL:(NSURL*)url; @end

AsyncImageView.m:

#import "AsyncImageView.h" @implementation AsyncImageView    - (id)initWithFrame:(CGRect)frame {     self = [super initWithFrame:frame];     if(self) {         // Initialization code     }     returnself; }    - (void)loadImageFromURL:(NSURL*)url {     if(connection!=nil) { [connection release]; }     if(data!=nil) { [data release]; }     NSURLRequest* request = [NSURLRequest requestWithURL:url                                              cachePolicy:NSURLRequestUseProtocolCachePolicy                                          timeoutInterval:60.0];     connection = [[NSURLConnection alloc]                   initWithRequest:request delegate:self]; }    - (void)connection:(NSURLConnection *)theConnection     didReceiveData:(NSData *)incrementalData {     if(data==nil) {         data =         [[NSMutableData alloc] initWithCapacity:2048];     }     [data appendData:incrementalData]; }    - (void)connectionDidFinishLoading:(NSURLConnection*)theConnection {        [connection release];     connection=nil;        if([[self subviews] count] > 0) {         [[[self subviews] objectAtIndex:0] removeFromSuperview];     }        UIImageView *imageView = [[[UIImageView alloc] initWithImage:[UIImage imageWithData:data]] autorelease];        imageView.contentMode = UIViewContentModeScaleAspectFit;     imageView.autoresizingMask = ( UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight );        [self addSubview:imageView];     imageView.frame = self.bounds;     [imageView setNeedsLayout];     [self setNeedsLayout];     [data release];     data=nil; }    - (UIImage*) image {     UIImageView* iv = [[self subviews] objectAtIndex:0];     return[iv image]; }    - (void)dealloc {     [connection cancel];     [connection release];     [data release];     [super dealloc]; } @end

使用：

AsyncImageView *asyncImage = [[AsyncImageView alloc] init]; asyncImage.frame = CGRectMake(100, point_y, 95, 95) //圓角 [asyncImage.layer setMasksToBounds:YES]; [asyncImage.layer setCornerRadius:15]; [asyncImage loadImageFromURL:[NSURL URLWithString:@"www.istar.name/...."]];

不過發現一個好東東， SDWebImage， 這個實在是太方便了
首頁：https://github.com/rs/SDWebImage
1.下載下來放到project裡面
2. 添加：MapKit.framework
3. #import “UIImageView+WebCache.h”
4. 使用：

UIImageView *asyncImage = [[UIImageView alloc] init]; [asyncImage setImageWithURL:[NSURL URLWithString:@www.istar.name/....]];

 

使用第三方庫

EGOImageLoading是我在項目中用的比較多的一個第三方圖片非同步載入類，你們可以在git上找到並下載它，連結如下。另外提一下，
廣為人知的下拉重新整理EGORefreshTableHeaderView也是就是這個人寫的。

https://github.com/enormego/EGOImageLoading
(下載後運行demo程式XCode會提示找不到EGOCache.h標頭檔，可以在這個地方下載https://github.com/enormego/EGOCache)

使用方法可以參照裡面的demo程式，很簡單，只要把ImageUrl告訴它，剩下的就什麼都不用管了，它會幫你非同步載入，還會做緩衝處理...

?1234     // 設定預設佔位圖片     myEgoimageView.placeholderImage = [UIImage imageNamed:@"placeholder.png"];     // 告訴它圖片的url地址, done     myEgoimageView.imageURL = [NSURL URLWithString:@"http://simg.cocoachina.com/201111220746561330.jpg"];