uitableview 异步加载image

转一个UITableView中异步加载图片方法

先说使用，再给定义

使用方法：

- (UITableViewCell *)tableView:(UITableView *)tableView
         cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    
    static NSString *CellIdentifier = @"ImageCell";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    
    if (cell == nil) {
        cell = [[[UITableViewCell alloc]
                 initWithFrame:CGRectZero reuseIdentifier:CellIdentifier]
                autorelease];
    } else {
        AsyncImageView* oldImage = (AsyncImageView*)
        [cell.contentView viewWithTag:999];
        [oldImage removeFromSuperview];
    }
    
    CGRect frame;
    frame.size.width=75; frame.size.height=75;
    frame.origin.x=0; frame.origin.y=0;
    AsyncImageView* asyncImage = [[[AsyncImageView alloc]
                                   initWithFrame:frame] autorelease];
    asyncImage.tag = 999;
    NSURL *url = [NSURL URLWithString: @"image url"];

    [asyncImage loadImageFromURL:url];
    [cell.contentView addSubview:asyncImage];

    return cell;
}

 

类的定义：

.h

#import <UIKit/UIKit.h>


@interface AsyncImageView : UIView {
    //could instead be a subclass of UIImageView instead of UIView, depending on what other features you want to 
    // to build into this class?
    
    NSURLConnection* connection; //keep a reference to the connection so we can cancel download in dealloc
    NSMutableData* data; //keep reference to the data so we can collect it as it downloads
    //but where is the UIImage reference? We keep it in self.subviews - no need to re-code what we have in the parent class
    
}

- (void)loadImageFromURL:(NSURL*)url;
- (UIImage*) image;
@end

 

.m

 

#import "AsyncImageView.h"

@implementation AsyncImageView

- (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];
    //TODO error handling, what if connection is nil?
}

- (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