Question

来自此代码

#import "AsyncImageView.h"
#import "ImageCache.h"
#import "ImageCacheObject.h"

static ImageCache *imageCache = nil;

@implementation AsyncImageView


- (id)initWithFrame:(CGRect)frame {
    if (self = [super initWithFrame:frame]) {
    }
    return self;
}


- (void)drawRect:(CGRect)rect {
    // Drawing code
}


- (void)dealloc {
    [connection cancel];
    [connection release];
    [data release];
    [super dealloc];
}

-(void)loadImageFromURL:(NSURL*)url {
    if (connection != nil) {
        [connection cancel];
        [connection release];
        connection = nil;
    }
    if (data != nil) {
        [data release];
        data = nil;
    }

    if (imageCache == nil) 
        imageCache = [[ImageCache alloc] initWithMaxSize:2*1024*1024]; 

    [urlString release];
    urlString = [[url absoluteString] copy];
    UIImage *cachedImage = [imageCache imageForKey:urlString];
    if (cachedImage != nil) 
    {   NSLog(@"get in");
        if ([[self subviews] count] > 0) 
        {
            [[[self subviews] objectAtIndex:0] removeFromSuperview];
        }
        UIImageView *imageView = [[[UIImageView alloc] initWithImage:cachedImage] autorelease];
        imageView.contentMode = UIViewContentModeScaleAspectFit;
        imageView.autoresizingMask = 
        UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
        [self addSubview:imageView];
        imageView.frame = self.bounds;
        [imageView setNeedsLayout]; 
        [self setNeedsLayout];
        return;
    }

#define SPINNY_TAG 5555   

    UIActivityIndicatorView *spinny = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
    spinny.tag = SPINNY_TAG;
    spinny.center = self.center;
    [spinny startAnimating];
    [self addSubview:spinny];
    [spinny release];

    NSURLRequest *request = [NSURLRequest requestWithURL:url 
                                             cachePolicy:NSURLRequestUseProtocolCachePolicy 
                                         timeoutInterval:60.0];
    connection = [[NSURLConnection alloc] initWithRequest:request delegate:self];
}

- (void)connection:(NSURLConnection *)connection 
    didReceiveData:(NSData *)incrementalData {
    if (data==nil) {
        data = [[NSMutableData alloc] initWithCapacity:2048];
    }
    [data appendData:incrementalData];
}

- (void)connectionDidFinishLoading:(NSURLConnection *)aConnection {
    [connection release];
    connection = nil;

    UIView *spinny = [self viewWithTag:SPINNY_TAG];
    [spinny removeFromSuperview];

    if ([[self subviews] count] > 0) {
        [[[self subviews] objectAtIndex:0] removeFromSuperview];
    }

    UIImage *image = [UIImage imageWithData:data];

    [imageCache insertImage:image withSize:[data length] forKey:urlString];

    UIImageView *imageView = [[[UIImageView alloc] 
                               initWithImage:image] autorelease];
    imageView.contentMode = UIViewContentModeScaleAspectFit;
    imageView.autoresizingMask = 
    UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
    [self addSubview:imageView];
    imageView.frame = self.bounds;
    [imageView setNeedsLayout]; // is this necessary if superview gets setNeedsLayout?
    [self setNeedsLayout];
    [data release];
    data = nil;
}

@end

如果我想从app源获取图片，如果url为空，我应该添加什么代码？

以下是来自xyz.m的更多代码

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"Cell";

    UITableViewCell *cell = [self.newsTable dequeueReusableCellWithIdentifier:
                             CellIdentifier];
    if (cell == nil) {
        //cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
        cell = [self getCellContentView:CellIdentifier];
    }
    else{
        AsyncImageView *oldImage = (AsyncImageView *)[cell.contentView viewWithTag:999];
        [oldImage removeFromSuperview];
    }
    int index = [indexPath indexAtPosition: [indexPath length] - 1];

    //Get Picture
    CGRect frame;
    frame.size.width=50; frame.size.height=50;
    frame.origin.x=10; frame.origin.y=0;
    AsyncImageView* asyncImage = [[[AsyncImageView alloc] initWithFrame:frame] autorelease];
    asyncImage.tag = 999;

    NSString *string = [jsonPic objectAtIndex:index];
    NSString *url=[string stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
    NSURL *imageURL = [NSURL URLWithString:url];
    if([string isEqualToString:@""]){
     NSLog(@"Not found");

在这里我不知道如何从源头获取图片

        AsyncImageView * NoImage = [[[AsyncImageView alloc] initWithFrame:frame] autorelease];
        NoImage.tag = 999;
        NoImage.image = [UIImage imageNamed:@"bl-noImg.gif"];
        [cell.contentView addSubview:NoImage];
    }
    else
    {   NSLog(@"image  URL %@",imageURL);
       [asyncImage loadImageFromURL:imageURL];
        [cell.contentView addSubview:asyncImage];

我可以从asyncImage获取图片

请帮助我或指导我这样做。谢谢。。。。现在一切都完成了，这是我的结果代码

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"Cell";

    UITableViewCell *cell = [self.newsTable dequeueReusableCellWithIdentifier:
                             CellIdentifier];
    if (cell == nil) {
        //cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
        cell = [self getCellContentView:CellIdentifier];
    }
    else{
        AsyncImageView *oldImage = (AsyncImageView *)[cell.contentView viewWithTag:999];
        [oldImage removeFromSuperview];
    }
    int index = [indexPath indexAtPosition: [indexPath length] - 1];

    //Get Picture
    CGRect frame;
    frame.size.width=50; frame.size.height=50;
    frame.origin.x=10; frame.origin.y=0;
    AsyncImageView* asyncImage = [[[AsyncImageView alloc] initWithFrame:frame] autorelease];
    asyncImage.tag = 999;

    NSString *string = [jsonPic objectAtIndex:index];
     if([string isEqualToString:@""]){
     //NSLog(@"Not found");
        UIImageView * NoImg = [[[UIImageView alloc] initWithFrame:frame] autorelease];
        NoImg.tag = 999;
        [NoImg setImage:[UIImage imageWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"bg-noImg" ofType:@"gif"]]];
        [cell.contentView addSubview:NoImg];
    }
    else
    {   //NSLog(@"image  URL %@",imageURL);
        NSString *url=[string stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
        NSURL *imageURL = [NSURL URLWithString:url];
        [asyncImage loadImageFromURL:imageURL];
        [cell.contentView addSubview:asyncImage];
    }

谢谢大家：）

Answer 1

如果要检查空URL，则应在调用loadImageFromURL之前检查它，甚至在创建NSURL对象之前。如果它不为空，那么你应该创建NSURL对象并调用loadImageFromURL方法。

代码中的某个地方......你从那里调用loadImageFromURL：

    if(urlString !=nil || [urlString length]>0)
    {
     create NSURL object
     now again check NSURL object whether its nil or not
     we are checking it because if the urlString has incorrect url pattern then no
 NSURLObject would be created, so if there is no NSURLObject then we should not call
 your method.
     if(NSURLObject !=nil)
     {
        call loadImageFromURL method and so on
     }
     else
     {
       //load some default image. which will convey no URL Found
     }

    }
    else
     {
       //load some default image. which will convey no URL Found
     }

谢谢，

AsyncImage从程序源获取图片？

1 个答案: