XML processing and online image display in iPhone

XML processing:

In iPhone development, the XML processing method is very different from. net. I personally feel that it is not as convenient as donot. The nsxmlparser class library is provided in the Apple SDK to parse XML. It requires a URL as the input parameter and parses the XML file through the nsxmlparser delegate method. Nsxmlparser mainly has three delegate methods to parse XML:

1. didstartelement

2. didendelement

3. foundcharacters

Didstartelement: This method is called when the parser object encounters the XML start mark.

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

Didstartelement:
This method is called when the parser object encounters an XML end mark.

-(void)parser:(NSXMLParser*)parser didEndElement:(NSString *)elementName     namespaceURI:(NSString*)namespaceURI qualifiedName:(NSString *)qNamefoundCharacters：

This method is called when the parser finds the character between the start mark and the end mark.

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

Display network images on the iPhone:

There are three steps to display an image through a URL:

1. Create an nsurl object through URL

2. Load image data to an nsdata object through the nsurl object

3. Assign the nsdata object to uiimage

NSURL *url = [NSURL URLWithString:@”www.cnblogs.com\images\sample.jpg”];NSData *data = [NSData dataWithContentsOfURL:url];UIImage *image = [[UIImage alloc] intiWithData:data];

Below we save the image address in an XML file on the server, parse the XML, parse the image address, and then display it.

Create a view based application named xmlwebimages

Open xmlwebimagesviewcontroller. h. Add a uiscrollview object property named webscrollview and add the iboutlet identifier.

#import <UIKit/UIKit.h> @interface XMLWebImageViewController : UIViewController {    IBOutlet UIScrollView *webScrollView;        }@property (nonatomic, retain) IBOutlet UIScrollView * webScrollView;@synthesize scrollView;

Create a class named xmlwebview and inherit the class of uiview. In this class, add the uiimageview attribute object, name it imageview, and add the iboutlet identifier.

@interface XMLWebView : UIView {     IBOutlet UIImageView *imageView;}@property (nonatomic, retain) IBOutlet UIImageView *imageView;@synthesize imageView; 

Create a. XIB file and place a uiimageview on it to associate it with the imageview in the code above.

Create an object class with only one attribute to store the image address:

@interface XMLWebElement: NSObject { UIImage *imgXML;}@property (nonatomic, retain) UIImage * imgXML;@end@synthesize image;

Now we create an XML file from the server, parse the XML file, and display the image code. Open xmlwebimagesviewcontroller. h and create an nsxmlparser object.
An array xmlelements that stores linked object objects. A temporary xmlwebelement object.

@interface XMLWebImagesViewController: UIViewController {     IBOutlet UIScrollView *scrollview;    NSXMLParser *xmlParser;    NSMutableString *currentNode;    NSMutableArray *xmlElements;    XMLWebElement *tempElement;} 

In the viewdidload method, allocate memory for xmlelements and initialize the XML address of the parser object:

- (void)viewDidLoad{     [super viewDidLoad];    xmlElements = [[NSMutableArray alloc] init];    xmlParser = [[NSXMLParser alloc] initWithContentsOfURL: [NSURL URLWithString:@"http://www.cnblogs.com/images.xml"]];    [xmlParser setDelegate:self];     [xmlParser parse];}

The XML structure on the server is as follows: the code for parsing the XML three methods is as follows:

<WebImages>   
<image>    
<URL>http://www.cnblogs.com/testimage1.jpg</URL>  
</image> 
<images>     
<URL>http://www.cnblogs.com/testimage2.jpg</URL> 
</images>
</WebImages>

The code for parsing the XML three delegate methods is as follows:

- (void)xmlParser:(NSXMLParser *)xmlParser didStartElement: (NSString *)elementName namespaceURI:(NSString *)namespaceURI  qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict{    if(![elementName compare:@"PictureInfo"])    {        tempElement = [[iCodeBlogXMLElement alloc] init];    }    else if(![elementName compare:@"imageURL"])    {        currentAttribute = [NSMutableString string];    }    else if(![elementName compare:@"imageTitle"])    {        currentAttribute = [NSMutableString string];    }}- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)   elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName{    if(![elementName compare:@"PictureInfo"])    {        [xmlElementObjects addObject:tempElement];    }    else if(![elementName compare:@"imageURL"])    {        NSURL *imageURL = [NSURL URLWithString:currentAttribute];        NSData *data =  [NSData dataWithContentsOfURL:imageURL];        UIImage *image = [[UIImage alloc] initWithData:data];        [tempElement setImage:image];    }    else if(![elementName compare:@"imageTitle"])    {       NSLog(@"The image title is %@", currentAttribute);        [tempElement setImageTitle:currentAttribute];    }    else if(![elementName compare:@"Pictures"])    {        [self layoutSubview];    }}- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string{    if(self.currentAttribute)    {        [self.currentAttribute appendString:string];    }} 

In this way, the image address in XML is parsed. The following code shows the image:

NSURL *url = [NSURL URLWithString：urlString];NSData *data = [NSData dataWithContentsOfURL:url];UIImage *image = [[UIImage alloc] intiWithData:data]; 

Summary:This article uses code to describe XML parsing and network slice display in the iPhone.