android - 如何使用 sax 显示 XML 解析

Question

我想使用此 URL 的 SAX 创建 xml 解析

http://news.google.com/?output=rss

但是我得到了错误，请检查并让我知道我在哪里做错了，或者如果我的问题有其他解决方案。

我在 GoogleNewsSaxActivity.class 中的这一行出错

for (int i = 0; i < baseParserData.getTitle().size(); i++) {

我的代码如下。

GoogleNewsSaxActivity.class

public class GoogleNewsSaxActivity extends Activity {

BaseFeedParser baseParserData;

 ArrayList<HashMap<String, String>> items = new ArrayList<HashMap<String, String>>();
    private myAdapter rssadaptor = null;
    ListView lview;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    try {
        SAXParserFactory saxPF = SAXParserFactory.newInstance();
        SAXParser saxP = saxPF.newSAXParser();
        XMLReader xmlR = saxP.getXMLReader();


        URL url = new URL("http://news.google.com/?output=rss");                                                            

        RssHandler myXMLHandler = new RssHandler();
        xmlR.setContentHandler(myXMLHandler);

        xmlR.parse(new InputSource(url.openStream()));


    } catch (Exception e) {
        System.out.println(e);
    }

    baseParserData = RssHandler.baseParserData;

    /** 
     * Run a for loop to set All the TextViews with text until 
     * the size of the array is reached.
     * 
     **/
    for (int i = 0; i < baseParserData.getTitle().size(); i++) {

        System.out.println("value of i==============>" + i);
        HashMap<String, String> map = new HashMap<String, String>();

        map.put("title", baseParserData.getTitle().get(i));
        //map.put("Artist", baseParserData.getArtist().get(i));
        //map.put("Contry", baseParserData.getCountry().get(i));

        items.add(map);

        rssadaptor = new myAdapter(GoogleNewsSaxActivity.this, items);
    }

    lview = (ListView) findViewById(R.id.listView);

    // Getting adapter by passing xml data ArrayList
    rssadaptor = new myAdapter(this, items);
    lview.setAdapter(rssadaptor);

}
} 

RssHandler.class

public class RssHandler extends DefaultHandler{

/*private List<BaseFeedParser> messages;
//private Message currentMessage;
private StringBuilder builder;*/


String elementValue = null;
Boolean elementOn = false;
public static BaseFeedParser baseParserData = null;

public static BaseFeedParser getBaseParserData() {

    return baseParserData;
}
public static void setBaseParserData(BaseFeedParser baseParserData) {

    RssHandler.baseParserData = baseParserData;
}

/*public List<BaseFeedParser> getMessages(){
    return this.messages;
}*/

@Override
public void startElement(String uri, String localName, String name,
        Attributes attributes) throws SAXException {
    elementOn = true;

    System.out.println("Hello this is startElement : =========>");

    if (localName.equals(BaseFeedParser.CHANNEL))
    {
        baseParserData = new BaseFeedParser();
    } else if (localName.equals(BaseFeedParser.ITEM)) {


    }
}

@Override
public void characters(char[] ch, int start, int length)
        throws SAXException {

    if (elementOn) {
        elementValue = new String(ch, start, length);
        elementOn = false;
    }

}


@Override
public void endElement(String uri, String localName, String qName)
        throws SAXException {

    elementOn = false;

    /** 
     * Sets the values after retrieving the values from the XML tags
     * */ 
    if (localName.equalsIgnoreCase(BaseFeedParser.TITLE))
        baseParserData.setTitle(elementValue);
    else if (localName.equalsIgnoreCase(BaseFeedParser.LINK))
        baseParserData.setLink(elementValue);
    else if (localName.equalsIgnoreCase(BaseFeedParser.PUB_DATE))
        baseParserData.setPubDate(elementValue);
    else if (localName.equalsIgnoreCase(BaseFeedParser.DESCRIPTION))
        baseParserData.setDescription(elementValue);

}


}

还有另外两个类 BaseFeedParser.class 和 myAdapter.class，BaseFeedParser 类包含 Getters/Setters 方法，myadapter 是自定义 ListView 的适配器类。

谢谢。

LOGCAT 中显示错误

05-31 09:42:25.693: I/System.out(279): java.net.SocketException: Permission denied
05-31 09:42:25.713: D/AndroidRuntime(279): Shutting down VM
05-31 09:42:25.713: W/dalvikvm(279): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
05-31 09:42:25.752: E/AndroidRuntime(279): FATAL EXCEPTION: main
05-31 09:42:25.752: E/AndroidRuntime(279): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.rahul.android.sax/com.rahul.android.sax.GoogleNewsSaxActivity}: java.lang.NullPointerException
05-31 09:42:25.752: E/AndroidRuntime(279):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
05-31 09:42:25.752: E/AndroidRuntime(279):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
05-31 09:42:25.752: E/AndroidRuntime(279):  at android.app.ActivityThread.access$2300(ActivityThread.java:125)
05-31 09:42:25.752: E/AndroidRuntime(279):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
05-31 09:42:25.752: E/AndroidRuntime(279):  at android.os.Handler.dispatchMessage(Handler.java:99)
05-31 09:42:25.752: E/AndroidRuntime(279):  at android.os.Looper.loop(Looper.java:123)
05-31 09:42:25.752: E/AndroidRuntime(279):  at android.app.ActivityThread.main(ActivityThread.java:4627)
05-31 09:42:25.752: E/AndroidRuntime(279):  at java.lang.reflect.Method.invokeNative(Native Method)
05-31 09:42:25.752: E/AndroidRuntime(279):  at java.lang.reflect.Method.invoke(Method.java:521)
05-31 09:42:25.752: E/AndroidRuntime(279):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
05-31 09:42:25.752: E/AndroidRuntime(279):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
05-31 09:42:25.752: E/AndroidRuntime(279):  at dalvik.system.NativeStart.main(Native Method)
05-31 09:42:25.752: E/AndroidRuntime(279): Caused by: java.lang.NullPointerException
05-31 09:42:25.752: E/AndroidRuntime(279):  at com.rahul.android.sax.GoogleNewsSaxActivity.onCreate(GoogleNewsSaxActivity.java:61)
05-31 09:42:25.752: E/AndroidRuntime(279):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
05-31 09:42:25.752: E/AndroidRuntime(279):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
05-31 09:42:25.752: E/AndroidRuntime(279):  ... 11 more

Answer 1

使用下面的代码。

站点列表.java

public class SitesList {

    /** Variables */
    private ArrayList<String> name = new ArrayList<String>();
    private ArrayList<String> website = new ArrayList<String>();
    private ArrayList<String> pubdate = new ArrayList<String>();
    private ArrayList<String> desc = new ArrayList<String>();

    /**
     * In Setter method default it will return arraylist change that to add
     */

    public ArrayList<String> getName() {
        return name;
    }

    public void setName(String name) {
        this.name.add(name);
    }

    public ArrayList<String> getWebsite() {
        return website;
    }

    public void setWebsite(String website) {
        this.website.add(website);
    }

    public ArrayList<String> getPubdate() {
        return pubdate;
    }

    public void setPubdate(String pubdate) {
        this.pubdate.add(pubdate);
    }

    public ArrayList<String> getDesc() {
        return desc;
    }

    public void setDesc(String desc) {
        this.desc.add(desc);
    }

}

MyXMLHandler.java

public class MyXMLHandler extends DefaultHandler {

    Boolean currentElement = false;
    String currentValue = null;
    public static SitesList sitesList = null;

    public static SitesList getSitesList() {
        return sitesList;
    }

    public static void setSitesList(SitesList sitesList) {
        MyXMLHandler.sitesList = sitesList;
    }

    /**
     * Called when tag starts ( ex:- <name>AndroidPeople</name> -- <name> )
     */
    @Override
    public void startElement(String uri, String localName, String qName,
            Attributes attributes) throws SAXException {

        currentElement = true;

        if (localName.equals("channel")) {
            /** Start */
            sitesList = new SitesList();
        }

    }

    /**
     * Called when tag closing ( ex:- <name>AndroidPeople</name> -- </name> )
     */
    @Override
    public void endElement(String uri, String localName, String qName)
            throws SAXException {

        currentElement = false;

        /** set value */
        if (localName.equalsIgnoreCase("title")) {
            sitesList.setName(currentValue);
        } else if (localName.equalsIgnoreCase("link")) {
            sitesList.setWebsite(currentValue);
        } else if (localName.equalsIgnoreCase("pubDate")) {
            sitesList.setPubdate(currentValue);
        } else if (localName.equalsIgnoreCase("description")) {
            sitesList.setDesc(currentValue);
        }
    }

    /**
     * Called to get tag characters ( ex:- <name>AndroidPeople</name> -- to get
     * AndroidPeople Character )
     */
    @Override
    public void characters(char[] ch, int start, int length)
            throws SAXException {

        if (currentElement) {
            currentValue = new String(ch, start, length);
            currentElement = false;
        }

    }

}

主 Activity .java

public class MainActivity extends Activity {
    SitesList sitesList = null;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        /** Create a new layout to display the view */
        LinearLayout layout = new LinearLayout(this);
        layout.setOrientation(1);

        /** Create a new textview array to display the results */
        TextView name[];
        TextView website[];
        TextView pubdate[];
        TextView desc[];

        try {

            /** Handling XML */
            SAXParserFactory spf = SAXParserFactory.newInstance();
            SAXParser sp = spf.newSAXParser();
            XMLReader xr = sp.getXMLReader();

            /** Send URL to parse XML Tags */
            URL sourceUrl = new URL(
                    "http://news.google.com/?output=rss");

            /** Create handler to handle XML Tags ( extends DefaultHandler ) */
            MyXMLHandler myXMLHandler = new MyXMLHandler();
            xr.setContentHandler(myXMLHandler);
            xr.parse(new InputSource(sourceUrl.openStream()));

        } catch (Exception e) {
            System.out.println("XML Pasing Exception = " + e);
        }

        /** Get result from MyXMLHandler SitlesList Object */
        sitesList = MyXMLHandler.sitesList;

        /** Assign textview array lenght by arraylist size */
        name = new TextView[sitesList.getName().size()];
        website = new TextView[sitesList.getWebsite().size()];
        pubdate = new TextView[sitesList.getPubdate().size()];
        desc = new TextView[sitesList.getDesc().size()];

        System.out.println("Hello Name size is:- " +sitesList.getName().size());
        System.out.println("Hello website size is:- " +sitesList.getWebsite().size());
        System.out.println("Hello pubdate size is:- " +sitesList.getPubdate().size());
        System.out.println("Hello desc size is:- " +sitesList.getDesc().size());


        /** Set the result text in textview and add it to layout */
        for (int i = 0; i < sitesList.getName().size(); i++) {
            name[i] = new TextView(this);
            name[i].setText("Name is = " + sitesList.getName().get(i));
            website[i] = new TextView(this);
            website[i].setText("Link is = " + sitesList.getWebsite().get(i));

            layout.addView(name[i]);
            layout.addView(website[i]);
        }

        /** Set the result text in textview and add it to layout */
        for (int i = 0; i < sitesList.getPubdate().size(); i++) {
            pubdate[i] = new TextView(this);
            pubdate[i].setText("Pub date is = "
                    + sitesList.getPubdate().get(i));

            desc[i] = new TextView(this);
            desc[i].setText("Desc is = "
                    + sitesList.getDesc().get(i));

            layout.addView(pubdate[i]);
            layout.addView(desc[i]);
        }

        /** Set the layout view to display */
        setContentView(layout);

    }
}