java - BlackBerry 中的 RSS/XML 解析

Question

我正在开发一个 RSS 阅读器应用程序，我需要在其中读取和显示部分数据。从 url https://twitter.com/statuses/user_timeline/27756405.rss 获取的数据中只需要提取 title 和 link 数据.

我在解析 xml 时遇到问题，需要有关此问题的帮助。

我的代码附在下面。

public class RssMain extends UiApplication {
    RssMain theApp;

    public static void main(String[] args) {
        // create an instance of our app
        RssMain theApp = new RssMain();
        // "run" the app
        theApp.enterEventDispatcher();
    }

    // app constructor
    public RssMain() {
        // create an instance of the main screen of our application
        RssScreen screen = new RssScreen();
        // make the screen visible
        UiApplication.getUiApplication().pushScreen(screen);
    }

    class RssScreen extends MainScreen {

        public RssScreen() {
            String rssUrl = "http://twitter.com/statuses/user_timeline/27756405.rss";
            String[][] urlData = RSSHandler.getURLFromRSS(rssUrl);
            for (int i = 0; i < urlData.length; i++) {
                String title = urlData[0][i];
                String url = urlData[1][i];
                System.out.println("TITLE " + title);
                System.out.println("URL " + url);

            }
        }
    }
}

RSSHandler 的实现

import java.io.IOException;
import java.io.InputStream;
import javax.microedition.io.Connector;
import javax.microedition.io.HttpConnection;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import net.rim.blackberry.api.browser.Browser;
import net.rim.device.api.ui.component.LabelField;
import net.rim.device.api.util.Arrays;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

class RSSHandler extends DefaultHandler {
    boolean isItem = false;
    boolean isTitle = false;
    boolean isLink = false;
    String[] title = new String[] {};
    String[] link = new String[] {};
    String value = "";

    public void startElement(String uri, String localName, String name, Attributes attributes) throws SAXException {
        if (!isItem) {
            if (name.equalsIgnoreCase("item"))
                isItem = true;
        } else {
            if (name.equalsIgnoreCase("title"))
                isTitle = true;
            if (name.equalsIgnoreCase("link"))
                isLink = true;
        }
    }

    public void characters(char[] ch, int start, int length) throws SAXException {
        if (isTitle || isLink) {
            value = value.concat(new String(ch, start, length));
        }
    }

    public void endElement(String uri, String localName, String name) throws SAXException {
        if (isItem && name.equalsIgnoreCase("item")) {
            isItem = false;
        }
        if (isTitle && name.equalsIgnoreCase("title")) {
            isTitle = false;
            Arrays.add(title, value);
            value = "";
        }
        if (isLink && name.equalsIgnoreCase("link")) {
            isLink = false;
            Arrays.add(link, value);
            value = "";
        }
    }

    public static String[][] getURLFromRSS(String url) {
        InputStream is = null;
        HttpConnection connection = null;
        RSSHandler rssHandler = new RSSHandler();
        try {
            connection = (HttpConnection) Connector.open(url);
            is = connection.openInputStream();
            try {
                SAXParser parser = SAXParserFactory.newInstance().newSAXParser();
                parser.parse(is, rssHandler);
            } catch (ParserConfigurationException e) {
                e.printStackTrace();
            } catch (SAXException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (is != null)
                    is.close();
                if (connection != null)
                    connection.close();

            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        String[][] result = new String[2][];
        result[0] = rssHandler.title;
        result[1] = rssHandler.link;
        return result;
    }
}

Answer 1

我使用与您的原理几乎相同的原理构建了一个非常粗略的应用程序，它正确地从以下位置加载数据:http://twitter.com/statuses/user_timeline/27756405.rss

请记住，这只是一个非常粗略的编辑。我目前无法访问黑莓开发工具，因此我已将其转换为独立的 Java 应用程序，但如果您更改它以适应您的黑莓应用程序，它应该可以正常工作。请注意在 parseRssData 方法中从 HttpConnection 切换到 URL，您可能必须将其切换回黑莓。

RssMain

public class RssMain {
    public static final String DEFAULT_URL = "http://twitter.com/statuses/user_timeline/27756405.rss";

    public static void main( String[ ] args ) {
        RssItem[ ] items = parseRssData( DEFAULT_URL );
        for( RssItem item : items ) System.out.println( "Title: " + item.title( ) + " | Link: " + item.link( ) );
    }

    public static RssItem[ ] parseRssData( String url ) {
        URL u;
        InputStream in = null;
        RssHandler handler = new RssHandler( );

        try {
            u = new URL( url );
            in = u.openStream( );

            SAXParser parser = SAXParserFactory.newInstance( ).newSAXParser( );
            parser.parse( in, handler );
        } catch( Exception cause ) {
            cause.printStackTrace( );
        }

        return handler.items.toArray( new RssItem[ 0 ] );
    }
}

RSS处理器

public class RssHandler extends DefaultHandler {
    public final ArrayList< RssItem > items;

    private boolean isItem = false;
    private boolean isTitle = false;
    private boolean isLink = false;

    String value = "";
    RssItem current = null;

    public RssHandler( ) {
        items = new ArrayList< RssItem >( );
    }

    @Override
    public void startElement( String uri, String localName, String name, Attributes attributes ) throws SAXException {
        if( !isItem  && name.equalsIgnoreCase( "item" ) ) isItem = true;
        else {
            if( name.equalsIgnoreCase( "title" ) ) isTitle = true;
            if( name.equalsIgnoreCase( "link" ) ) isLink = true;
        }
    }

    @Override
    public void endElement( String uri, String localName, String name ) {
        if( isItem && name.equalsIgnoreCase( "item" ) ) isItem = false;
        else if( isTitle || isLink ) {
            if( current == null ) current = new RssItem( );

            if( name.equalsIgnoreCase( "title" ) ) {
                isTitle = false;
                current.title( value );
            } else if( name.equalsIgnoreCase( "link" ) ) {
                isLink = false;
                current.link( value );
            }

            value = "";
            if( ( current.title( ) != null ) && ( current.link( ) != null ) ) {
                items.add( current );
                current = null;
            }
        }
    }

    @Override
    public void characters( char[ ] chars, int start, int length ) throws SAXException {
        if( isTitle || isLink ) value = value.concat( new String( chars, start, length ) );
    }
}

RSS 项

public class RssItem {
    private String title;
    private String link;

    public String title( ) {
        return title;
    }

    public RssItem title( String title ) {
        this.title = title;
        return this;
    }

    public String link( ) {
        return link;
    }

    public RssItem link( String link ) {
        this.link = link;
        return this;
    }
}