Question

我使用了以下代码。在这段代码中，我将展示来自Web服务的图像。为了提高tabelview的滚动速度，我使用UIImageView + WebCache，它可以快速提高滚动速度，但是当我触摸imageview时会显示图像。如何在显示tabelview时显示图像

NSString *str=[self.uploadimagearry objectAtIndex:indexPath.row];
// NSString *str1=[str stringByReplacingOccurrencesOfString:@" " withString:@"%20"];
NSURL *uploadimageURL = [NSURL URLWithString:[str stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];
// NSData *imgdata=[NSData dataWithContentsOfURL:uploadimageURL];

//UIImage * uploadimage = [UIImage imageWithData:imgdata];
cell.imageView.frame=CGRectMake(0, -15, 50, 35);
//[cell.imageView setImageWithURL:uploadimageURL]; 
[cell.imageView setImageWithURL:uploadimageURL];

Answer 1

您必须在不同的运行循环中启动NSUrlConnection，以便在表滚动时接收数据。

请查看以下示例：

<强> LazyTableImages

Lazy loading multiple images on background threads on the iPhone

Answer 2

//JImage.h

#import <Foundation/Foundation.h>


@interface JImage : UIImageView {

    NSURLConnection *connection;

    NSMutableData* data;

    UIActivityIndicatorView *ai;
}

-(void)initWithImageAtURL:(NSURL*)url;  

@property (nonatomic, retain) NSURLConnection *connection;

@property (nonatomic, retain) NSMutableData* data;

@property (nonatomic, retain) UIActivityIndicatorView *ai;

@end



//JImage.m

#import "JImage.h"

@implementation JImage
@synthesize ai,connection, data;

-(void)initWithImageAtURL:(NSURL*)url {


    [UIApplication sharedApplication].networkActivityIndicatorVisible = YES;

    [self setContentMode:UIViewContentModeScaleToFill];

    if (!ai){

        [self setAi:[[UIActivityIndicatorView alloc]   initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge]]; 

        [ai startAnimating];

        [ai setFrame:CGRectMake(27.5, 27.5, 20, 20)];

        [ai setColor:[UIColor blackColor]];

        [self addSubview:ai];
    }
    NSURLRequest* request = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:60];

    connection = [[NSURLConnection alloc] initWithRequest:request delegate:self];    
}


- (void)connection:(NSURLConnection *)theConnection didReceiveData:(NSData *)incrementalData {

    if (data==nil) data = [[NSMutableData alloc] initWithCapacity:5000];

    [data appendData:incrementalData];

    NSNumber *resourceLength = [NSNumber numberWithUnsignedInteger:[data length]];

    NSLog(@"resourceData length: %d", [resourceLength intValue]);

}
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error 
{
    NSLog(@"Connection error...");

    [UIApplication sharedApplication].networkActivityIndicatorVisible = NO;

    [ai removeFromSuperview];

}
- (void)connectionDidFinishLoading:(NSURLConnection*)theConnection 
{
    [UIApplication sharedApplication].networkActivityIndicatorVisible = NO;

    [self setImage:[UIImage imageWithData: data]];

    [ai removeFromSuperview];   
}
@end



//Include the definition in your class where you want to use the image
-(UIImageView*)downloadImage:(NSURL*)url:(CGRect)frame {

   JImage *photoImage=[[JImage alloc] init]; 

   photoImage.backgroundColor = [UIColor clearColor]; 

   [photoImage setFrame:frame];

   [photoImage setContentMode:UIViewContentModeScaleToFill]; 

   [photoImage initWithImageAtURL:url];

    return photoImage;
} 


//How to call the class

UIImageView *imagV=[self downloadImage:url :rect]; 

//you can call the downloadImage function in looping statement and subview the returned  imageview. 
//it will help you in lazy loading of images.


//Hope this will help

在tableview上显示来自webservice的图像

2 个答案: