Question

我在不同的网页上有UILabel和UIButton，我想从xml文件中读取他们的标题，但是我获得了NULL价值，在XML parser课程中，当我使用NSLOG时，我得到了答案，但是当我想要设置它们时，我有NULL，请你帮助我在这个实现中？

提前致谢！

我的XML解析器：

- (Presentation1NameXML *) initXMLParser {

appDelegate = (testAppDelegate *)[[UIApplication sharedApplication] delegate];

return self;
}

- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName
namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qualifiedName
attributes:(NSDictionary *)attributeDict {


if ([elementName isEqualToString:@"Presentation1Name"]) {
    appDelegate.books = [[NSMutableArray alloc] init];
    NSLog(@"The Prices Count");
}
else if ([elementName isEqualToString:@"Presentation"]) {
    presentation = [[Presentation alloc] init];
    presentation.pLabel = [attributeDict objectForKey:@"label"];
    NSLog(@"khengggg %@",presentation.pLabel);
//    }else if ([elementName isEqualToString:@"Slides"]){
//        slides = [[Slide alloc] init];
}

if([elementName isEqualToString:@"slide"]) {

            slid = [[Slide alloc] init];
            NSLog(@"Processing Element: %@", elementName);

            slid.index = [[attributeDict objectForKey:@"index"] integerValue];
           NSLog(@"Reading index value :%i", slid.index);


            slid.sLabel = [attributeDict objectForKey:@"label"];
            NSLog(@"Reading label value :%@", slid.sLabel);

            slid.identifier = [attributeDict objectForKey:@"identifier"];
        NSLog(@"Reading identifier value :%@", slid.identifier);

       }
      NSLog(@"Processing Element: %@", elementName);
    }


- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string {

if(!currentElementValue)
    currentElementValue = [[NSMutableString alloc] initWithString:string];
else
    [currentElementValue appendString:string];

NSLog(@"Processing Value: %@", currentElementValue);

}

- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName
 namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName {
if([elementName isEqualToString:@"Presentation1Name"]){
    return;

}

if([elementName isEqualToString:@"Presentation"]) {
    [appDelegate.books addObject:presentation];
    presentation = nil;

}

//    if ([elementName isEqualToString:@"Slides"]){
//        [appDelegate.books addObject:slides];
//        slides = nil;
//        return;
//    }

if ([elementName isEqualToString:@"slide"]){
    [appDelegate.books addObject:slid];
    slid = nil;

}else
    [presentation setValue:currentElementValue forKey:@"pLabel"];
    //[presentation setValue:currentElementValue forKey:elementName];
currentElementValue = nil;
}

我的标签代码：我得到了（null）

appDelegate = (testAppDelegate *)[[UIApplication sharedApplication] delegate];
label.textColor = [UIColor greenColor];
Presentation *p1 = [appDelegate.books objectAtIndex:0];
NSLog(@"aaaaaaaaa aaaa %@", p1);
label.text = p1.pLabel;

我的按钮代码：我得到了（null）

 UIButton *btn = [UIButton buttonWithType:UIButtonTypeCustom];
    Slide *s1 = [appDelegate.books objectAtIndex:0];
    NSLog(@" test %@", s1.sLabel);

我的对象类演示文稿link

我的对象类幻灯片link

My XML file

Answer 1

问题出在这里

if ([elementName isEqualToString:@"Presentation1Name"]) {
    appDelegate.books = [[NSMutableArray alloc] init];
    NSLog(@"The Prices Count");
}

没有这样的标签（Presentation1Name），永远不会创建数组。

Answer 2

如果要检查NULL值，可以使用此代码

[str isEqual:[NSNull null]

如果Web服务中的值为NULL，则返回此值。

希望这能帮到你！

Answer 3

在函数didStartElement中修改你的代码，没有这个标签'Presentation1Name'

if ([elementName isEqualToString:@"Presentation"]) {
    appDelegate.books = [[NSMutableArray alloc] init];
    NSLog(@"The Prices Count");
}

和在函数didEndElement中你应该删除这一行：

[presentation setValue:currentElementValue forKey:@"pLabel"];

还有一些内存泄漏，你应该在addObject

之后发布

if([elementName isEqualToString:@"Presentation"]) {
    [appDelegate.books addObject:presentation];
    [presentation release];
    presentation = nil;

}
if ([elementName isEqualToString:@"slide"]){
    [appDelegate.books addObject:slid];
    [slid release];
    slid = nil;
}

你应该释放希望它有用..

在读取xml文件时，NULL值而不是UILabel和UIButton标题（Objective-C）

3 个答案: