单击列表视图中的项目，以调出新视图

Question

我目前正在制作一个解析RSS Feed的应用程序。 我使用了XML拉式解析器，以便将Feed中的信息显示到Listview 。 我想创建一个新活动，当用户单击ListView中的任何已分析标题时启动。 在新活动中，我希望从RSS feed中解析出更多信息，这些信息与刚刚单击的项目有关。

我尝试了几种尝试来尝试显示新视图，但不幸的是，该应用程序一直崩溃。 单击列表中的项目后，可以在对话框中显示所需的其他信息。

这是我的代码，底部的最后一部分是我试图将其链接到新视图的位置。

      public class RssFeed extends ListActivity {


  List titles;
  List description;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.rss);

    titles = new ArrayList();
    description = new ArrayList();

    try {
        URL url = new        URL("www.sample.com");

        XmlPullParserFactory factory = XmlPullParserFactory.newInstance();
        factory.setNamespaceAware(false);
        XmlPullParser xpp = factory.newPullParser();
        xpp.setInput(getInputStream(url), "UTF_8");
        boolean insideItem = false;

        /** While the rss feed has not displayed end_document, pull the title and description information */
        int eventType = xpp.getEventType();
        while (eventType != XmlPullParser.END_DOCUMENT) {
            if (eventType == XmlPullParser.START_TAG) {

                if (xpp.getName().equalsIgnoreCase("item")) {
                    insideItem = true;
                } else if (xpp.getName().equalsIgnoreCase("title")) {
                    if (insideItem)
                        titles.add(xpp.nextText()); 
                } else if (xpp.getName().equalsIgnoreCase("description")) {
                    if (insideItem)
                        description.add(xpp.nextText()); 
                }
            }else if(eventType==XmlPullParser.END_TAG && xpp.getName().equalsIgnoreCase("item")){
                insideItem=false;
            }

            eventType = xpp.next(); 
        }


    } catch (MalformedURLException e) {
        e.printStackTrace();
    } catch (XmlPullParserException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }


    ArrayAdapter adapter = new ArrayAdapter(this,
            android.R.layout.simple_list_item_1, titles);
    setListAdapter(adapter);



        }

        public InputStream getInputStream(URL url) {
                   try {
                       return url.openConnection().getInputStream();
                   } catch (IOException e) {
                       return null;
                     }
                }

      //When the user clicks on a list this runs
     protected void onListItemClick(ListView l, View v, int position, long id) {
     Intent intent = new Intent(getActivity(), Descriptions.class);
                startActivity(intent);

新活动仅包含用于设置视图的代码。

    import android.os.Bundle;
    import android.app.Activity;


    public class Descriptions extends Activity {


        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
             setContentView(R.layout.description);
}
    }

原木猫-

04-03 19:31:03.446: D/dalvikvm(564): GC freed 8121 objects / 330568 bytes in 85ms
04-03 19:31:09.856: D/AndroidRuntime(564): Shutting down VM
04-03 19:31:09.856: W/dalvikvm(564): threadid=3: thread exiting with uncaught exception (group=0x4001b188)
04-03 19:31:09.856: E/AndroidRuntime(564): Uncaught handler: thread main exiting due to uncaught exception
04-03 19:31:09.876: E/AndroidRuntime(564): java.lang.NullPointerException
04-03 19:31:09.876: E/AndroidRuntime(564):  at android.content.ComponentName.<init>(ComponentName.java:75)
04-03 19:31:09.876: E/AndroidRuntime(564):  at android.content.Intent.<init>(Intent.java:2551)
04-03 19:31:09.876: E/AndroidRuntime(564):  at org.me.myandroidstuff.TrafficScotlandPrototype.RssFeed.onListItemClick(RssFeed.java:109)
04-03 19:31:09.876: E/AndroidRuntime(564):  at android.app.ListActivity$2.onItemClick(ListActivity.java:312)
04-03 19:31:09.876: E/AndroidRuntime(564):  at android.widget.AdapterView.performItemClick(AdapterView.java:284)
04-03 19:31:09.876: E/AndroidRuntime(564):  at android.widget.ListView.performItemClick(ListView.java:3285)
04-03 19:31:09.876: E/AndroidRuntime(564):  at android.widget.AbsListView$PerformClick.run(AbsListView.java:1640)
04-03 19:31:09.876: E/AndroidRuntime(564):  at android.os.Handler.handleCallback(Handler.java:587)
04-03 19:31:09.876: E/AndroidRuntime(564):  at android.os.Handler.dispatchMessage(Handler.java:92)
04-03 19:31:09.876: E/AndroidRuntime(564):  at android.os.Looper.loop(Looper.java:123)
04-03 19:31:09.876: E/AndroidRuntime(564):  at android.app.ActivityThread.main(ActivityThread.java:4363)
04-03 19:31:09.876: E/AndroidRuntime(564):  at java.lang.reflect.Method.invokeNative(Native Method)
04-03 19:31:09.876: E/AndroidRuntime(564):  at java.lang.reflect.Method.invoke(Method.java:521) 
04-03 19:31:09.876: E/AndroidRuntime(564):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860) 
04-03 19:31:09.876: E/AndroidRuntime(564):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618) 
04-03 19:31:09.876: E/AndroidRuntime(564):  at dalvik.system.NativeStart.main(Native Method)
04-03 19:31:09.896: I/dalvikvm(564): threadid=7: reacting to signal 3
04-03 19:31:09.906: I/dalvikvm(564): Wrote stack trace to '/data/anr/traces.txt'

Answer 1

您必须按照创建的意图提供活动的上下文。

所以你的代码会像这样

public void registerCallClickBack() {
        ListView list = (ListView) findViewById(your list);
        list.setOnItemClickListener(new AdapterView.OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> parent, View viewClicked,
                    int position, long id) {
                Intent intent = new Intent(MainActivity.this, Descriptions.class);
                startActivity(intent);
            }
        });
    } 

在onCreate方法的MainActivity中，您需要

public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
             setContentView(R.layout.description);
             registerCallClickBack();

Answer 2

我要说的一件事是为onListItemClick编写@Override标记，因为您要重写它。 清单文件中是否还声明了Descriptions.java？