Iphone UITableView的异步下载问题&；阿西特

我尝试使用ASIHTT在UITableView上加载一些图像，但遇到了一些问题。首先，我读取一个xml文件（使用tbxml），然后将标题、图像路径和描述保存在字典中，然后保存在数组中，为了进行解析，我使用以下代码：

- (void)loadUnknownXML {    
    // Load and parse the books.xml file
    tbxml = [TBXML tbxmlWithURL:[NSURL URLWithString:@"http://www.xxx.com"]];

    // If TBXML found a root node, process element and iterate all children
    if (tbxml.rootXMLElement){
        [self traverseElement:tbxml.rootXMLElement];
    }
}

- (void) traverseElement:(TBXMLElement *)element {

    TBXMLElement *child = element->firstChild;
    TBXMLElement *items = [TBXML childElementNamed:@"item" parentElement:child];

    do{
        if (items->firstChild) {

            TBXMLElement *titolo = [TBXML childElementNamed:@"title" parentElement:items];
            TBXMLElement *descrizione = [TBXML childElementNamed:@"description" parentElement:items];
            //NSLog(@"Titolo: %@ \n Descrizione: %@",[TBXML textForElement:titolo],[TBXML textForElement:descrizione]);

            self.elemento = [[NSMutableDictionary alloc] init];
            [self.elemento setObject:[TBXML textForElement:titolo] forKey:@"Titolo"];

            NSString *indirizzoImmagine = [TBXML textForElement:descrizione];
            NSRange rangeSRC = [indirizzoImmagine rangeOfString:@"src=\""];
            indirizzoImmagine = [indirizzoImmagine substringFromIndex:NSMaxRange(rangeSRC)];
            NSRange rangeAMP = [indirizzoImmagine rangeOfString:@"&amp"];
            NSRange rangeWidth = [indirizzoImmagine rangeOfString:@"&width"];
            if (rangeAMP.location != NSNotFound) {
                indirizzoImmagine = [indirizzoImmagine substringToIndex:NSMaxRange(rangeAMP)];
            }
            else if (rangeWidth.location != NSNotFound){
                indirizzoImmagine = [indirizzoImmagine substringToIndex:NSMaxRange(rangeWidth)];
            }        
            indirizzoImmagine = [indirizzoImmagine stringByReplacingOccurrencesOfString:@"&amp" withString:@""];
            indirizzoImmagine = [indirizzoImmagine stringByReplacingOccurrencesOfString:@"&width" withString:@""];



            [self.elemento setObject:indirizzoImmagine forKey:@"IndirizzoImmagine"];

            [self.elemento setObject:[TBXML textForElement:descrizione] forKey:@"Descrizione"];
            [self.array addObject:self.elemento];
        }

    }
    while ((items=items->nextSibling));

}

然后我从下载开始

- (void) loadURL:(NSURL *)url index:(int)index
{

    ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];


    ASIDownloadCache *cache = [[ASIDownloadCache alloc] init];

    [request setDownloadCache:cache];
    [request setCacheStoragePolicy:ASICachePermanentlyCacheStoragePolicy];
    [request setCachePolicy:ASIOnlyLoadIfNotCachedCachePolicy];

    [cache setStoragePath:@"/Users/kikko/kikko/xxx"];

    request.userInfo = [NSDictionary dictionaryWithObjectsAndKeys: 
                        [NSNumber numberWithInt:index], @"index",
                        url, @"url", nil];


    [request setDelegate:self];
    [request startAsynchronous];

}


    - (void)requestFinished:(ASIHTTPRequest *)request
    {

        int index = [[request.userInfo valueForKey:@"index"] intValue];

    ASIDownloadCache *cache = [[ASIDownloadCache alloc] init];  
    [cache setStoragePath:@"/Users/kikko/kikko/xxx"];

    [request.userInfo valueForKey:@"url"];

    if ([cache cachedResponseDataForURL:[request.userInfo valueForKey:@"url"]]==nil) {

        NSLog(@"%@",[request.userInfo valueForKey:@"url"]);

        NSIndexPath* indexPath = [NSIndexPath indexPathForRow:index inSection:0];
        NSArray* rows = [NSArray arrayWithObjects:indexPath, nil];
        [table reloadRowsAtIndexPaths:rows withRowAnimation:UITableViewRowAnimationNone];

    }

    }

    - (void)requestFailed:(ASIHTTPRequest *)request
    {
        NSError *error = [request error];
        NSLog(@"Error: %@",error);

    }

最后，我将图像放入cell.imageview中

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {

    return 1;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    return self.array.count;
}

- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
    return 50;
}

-(NSString *) stringByStrippingHTML:(NSString *)stringa {

    NSRange r;

    NSString *str = stringa;
    while ((r = [str rangeOfString:@"<[^>]+>" options:NSRegularExpressionSearch]).location != NSNotFound)
        str = [str stringByReplacingCharactersInRange:r withString:@""];
    return str; 
}

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

UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (!cell) {
    cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier];
}

elemento = [array objectAtIndex:indexPath.row];

NSURL *indirizzoImmagine = [NSURL URLWithString:[elemento objectForKey:@"IndirizzoImmagine"]];

[self loadURL:indirizzoImmagine index:indexPath.row];

ASIDownloadCache *cache = [[ASIDownloadCache alloc] init];
[cache setStoragePath:@"/Users/kikko/kikko/xxx"];

dataImmagine = [cache cachedResponseDataForURL:indirizzoImmagine];

[cell.imageView setImage:[UIImage imageWithData:dataImmagine]];

cell.textLabel.text = [elemento objectForKey:@"Titolo"];

return cell;

-（NSInteger）节数表视图：（UITableView*）表视图{
返回1；
}
-（NSInteger）表视图：（UITableView*）表视图行数节：（NSInteger）节{
返回self.array.count；
}
-（CGFloat）tableView:（UITableView*）表视图行高度索引路径：（NSIndexPath*）索引路径
{
返回50；
}
-（NSString*）stringByStrippingHTML:（NSString*）stringa{
NSRange；
NSString*str=stringa；
while（（r=[str rangeOfString:@“]+>”选项：NSRegularExpressionSearch]）。位置！=NSNotFound）
str=[str STRINGBYREPLAcingCharactersRange:r with string:@''；
返回str；
}
-（UITableViewCell*）tableView:（UITableView*）tableView cellForRowAtIndexPath:（NSIndexPath*）indexPath{
静态NSString*CellIdentifier=@“ItemCell”；
UITableViewCell*单元格=[tableView dequeueReusableCellWithIdentifier:CellIdentifier]；
如果（！单元格）{
cell=[[UITableViewCell alloc]initWithStyle:UITableViewCellStyleSubtitle重用标识符：CellIdentifier]；
}
elemento=[array objectAtIndex:indexath.row]；
NSURL*INDIRIZOIMGINE=[NSURL URLWithString:[elemento objectForKey:@“INDIRIZOIMGINE”]；
[self-loadURL:IndirizzoimEngine索引：indexPath.row]；
ASIDownloadCache*cache=[[ASIDownloadCache alloc]init]；
[缓存设置存储路径：@”/Users/kikko/kikko/xxx]；
DataImEngine=[cache CachedResponsaForUrl:IndirizzoImEngine]；
[cell.imageView setImage:[UIImage-imageWithData:dataImmagine]]；
cell.textlab.text=[elemento objectForKey:@“Titolo”]；
返回单元；

---

}

苹果公司给出了一个下载和显示图像的最佳例子

---

同时，我也将检查您的代码

有很多方法可以做到这一点，但对现有代码最简单的方法是将userinfo字典附加到您的请求对象

在遍历方法中，请执行以下操作：

//...
while ((items=items->nextSibling));
for (int i = 0; i < [self.array count]; i++)
{
    [arrayData addObject:[NSNull null]];
}

在单元格代码中，执行以下操作：

if ([arrayData objecAtIndex:indexPath.row] != [NSNull null]) {
         UIImage *img = [UIImage imageWithData:[self.arrayData objectAtIndex:indexPath.row]];
         imageView.image = img;
         [cell.imageView setImage:img];        
    } else {

        imageView.image = nil;
    }

---

非常感谢，我还有另一个问题，用这种方式获取图像我必须向下滚动然后向上滚动，如何在下载图像时重新加载显示图像的表格数据？编辑答案。在requestFinished方法中，您需要调用reloadRowsAtIndexPath:：根据列表的大小，您将遇到内存问题。而不是将图像存储在数组中。。。您应该直接从cellForRowAtIndexPath方法调用loadUrl:index:method，并在返回时使用ReloadRowSatineXPath调用。您可以完全跳过将其添加到arrayData。你缓存了图像，所以第二次应该会很快。事实上，我花了很多内存，：（我有大约200/300个项目，我不明白我该怎么做你说的？我还有一个问题，表格有200/300个项目，但是当我破坏表格时，我只显示10/15个项目，然后我显示e“加载更多…”如果我在创建和单击“加载更多”时重新加载一个表，这可能是一个好主意？完全去掉arrayData，而是从ASI下载缓存中获取图像。有一种方法可以直接从缓存中获取图像文件。

if ([arrayData objecAtIndex:indexPath.row] != [NSNull null]) {
         UIImage *img = [UIImage imageWithData:[self.arrayData objectAtIndex:indexPath.row]];
         imageView.image = img;
         [cell.imageView setImage:img];        
    } else {

        imageView.image = nil;
    }