java - 为什么没有显示检索到的数据

Question

我想从 http://api.eventful.com/rest/events/search?app_key=42t54cX7RbrDFczc&location=singapore 中检索数据.“title”、“start_time”、“longitude”、“latitude”下的标签。但是不知道为什么加了经纬度后显示不出来。

这是来自 logcat:

08-07 17:17:44.190: E/AndroidRuntime(23734): FATAL EXCEPTION: main
08-07 17:17:44.190: E/AndroidRuntime(23734): java.lang.NullPointerException
08-07 17:17:44.190: E/AndroidRuntime(23734):    at com.example.eventfulmaptry.MainActivity$ItemAdapter.getView(MainActivity.java:147)
08-07 17:17:44.190: E/AndroidRuntime(23734):    at android.widget.AbsListView.obtainView(AbsListView.java:1618)
08-07 17:17:44.190: E/AndroidRuntime(23734):    at android.widget.ListView.measureHeightOfChildren(ListView.java:1241)
08-07 17:17:44.190: E/AndroidRuntime(23734):    at android.widget.ListView.onMeasure(ListView.java:1152)
08-07 17:17:44.190: E/AndroidRuntime(23734):    at android.view.View.measure(View.java:8513)
08-07 17:17:44.190: E/AndroidRuntime(23734):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3143)
08-07 17:17:44.190: E/AndroidRuntime(23734):    at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1017)
08-07 17:17:44.190: E/AndroidRuntime(23734):    at android.widget.LinearLayout.measureVertical(LinearLayout.java:386)
08-07 17:17:44.190: E/AndroidRuntime(23734):    at android.widget.LinearLayout.onMeasure(LinearLayout.java:309)
08-07 17:17:44.190: E/AndroidRuntime(23734):    at android.view.View.measure(View.java:8513)
08-07 17:17:44.190: E/AndroidRuntime(23734):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3143)
08-07 17:17:44.190: E/AndroidRuntime(23734):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:250)
08-07 17:17:44.190: E/AndroidRuntime(23734):    at android.view.View.measure(View.java:8513)
08-07 17:17:44.190: E/AndroidRuntime(23734):    at android.widget.LinearLayout.measureVertical(LinearLayout.java:531)
08-07 17:17:44.190: E/AndroidRuntime(23734):    at android.widget.LinearLayout.onMeasure(LinearLayout.java:309)
08-07 17:17:44.190: E/AndroidRuntime(23734):    at android.view.View.measure(View.java:8513)
08-07 17:17:44.190: E/AndroidRuntime(23734):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3143)
08-07 17:17:44.190: E/AndroidRuntime(23734):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:250)
08-07 17:17:44.190: E/AndroidRuntime(23734):    at android.view.View.measure(View.java:8513)
08-07 17:17:44.190: E/AndroidRuntime(23734):    at android.view.ViewRoot.performTraversals(ViewRoot.java:857)
08-07 17:17:44.190: E/AndroidRuntime(23734):    at android.view.ViewRoot.handleMessage(ViewRoot.java:1878)
08-07 17:17:44.190: E/AndroidRuntime(23734):    at android.os.Handler.dispatchMessage(Handler.java:99)
08-07 17:17:44.190: E/AndroidRuntime(23734):    at android.os.Looper.loop(Looper.java:130)
08-07 17:17:44.190: E/AndroidRuntime(23734):    at android.app.ActivityThread.main(ActivityThread.java:3691)
08-07 17:17:44.190: E/AndroidRuntime(23734):    at java.lang.reflect.Method.invokeNative(Native Method)
08-07 17:17:44.190: E/AndroidRuntime(23734):    at java.lang.reflect.Method.invoke(Method.java:507)
08-07 17:17:44.190: E/AndroidRuntime(23734):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:912)
08-07 17:17:44.190: E/AndroidRuntime(23734):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:670)
08-07 17:17:44.190: E/AndroidRuntime(23734):    at dalvik.system.NativeStart.main(Native Method)

这是我的代码:

public class MainActivity extends Activity {

    ArrayList<String> title;
    ArrayList<String> start_time;
    ArrayList<String> latitude;
    ArrayList<String> longitude;

    ItemAdapter adapter1;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        ListView list = (ListView) findViewById(R.id.list);
        title = new ArrayList<String>();
        latitude = new ArrayList<String>();  
        longitude = new ArrayList<String>(); 
        try {

            URL url = new URL(
                    "http://api.eventful.com/rest/events/search?app_key=42t54cX7RbrDFczc&location=singapore");
            DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
            DocumentBuilder db = dbf.newDocumentBuilder();
            Document doc = db.parse(new InputSource(url.openStream()));
            doc.getDocumentElement().normalize();

            NodeList nodeList = doc.getElementsByTagName("event");
            for (int i = 0; i < nodeList.getLength(); i++) {

                Node node = nodeList.item(i);       

                Element fstElmnt = (Element) node;

                NodeList nameList = fstElmnt.getElementsByTagName("title");
                Element nameElement = (Element) nameList.item(0);
                nameList = nameElement.getChildNodes();         
                title.add(""+ ((Node) nameList.item(0)).getNodeValue());

                NodeList websiteList = fstElmnt.getElementsByTagName("start_time");
                Element websiteElement = (Element) websiteList.item(0);
                websiteList = websiteElement.getChildNodes();
                start_time.add(""+ ((Node) websiteList.item(0)).getNodeValue());           

                NodeList websiteList1 = fstElmnt.getElementsByTagName("latitude");
                Element websiteElement1 = (Element) websiteList1.item(0);
                websiteList1 = websiteElement1.getChildNodes();
                latitude.add(""+ ((Node) websiteList1.item(0)).getNodeValue());           


                NodeList websiteList2 = fstElmnt.getElementsByTagName("longitude");
                Element websiteElement2 = (Element) websiteList2.item(0);
                websiteList2 = websiteElement2.getChildNodes();
                longitude.add(""+ ((Node) websiteList2.item(0)).getNodeValue()); 




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

        adapter1 = new ItemAdapter(this);
        list.setAdapter(adapter1);
    }


    class ItemAdapter extends BaseAdapter {

        final LayoutInflater mInflater;

        private class ViewHolder {
            public TextView title_text;
            public TextView des_text;
            public TextView lat_text;
            public TextView long_text;


        }

        public ItemAdapter(Context context) {
            // TODO Auto-generated constructor stub
            super();
            mInflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);     
        }

        //@Override
        public int getCount() {
            return title.size();
        }

        //@Override
        public Object getItem(int position) {
            return position;
        }

        //@Override
        public long getItemId(int position) {
            return position;
        }

        //@Override
        public View getView(final int position, View convertView, ViewGroup parent) {
            View view = convertView;
            final ViewHolder holder;
            if (convertView == null) {
                view = mInflater.inflate(R.layout.mainpage_list,parent, false);
                holder = new ViewHolder();
                holder.title_text = (TextView) view.findViewById(R.id.title_text);
                holder.des_text = (TextView) view.findViewById(R.id.des_text);
                holder.lat_text = (TextView) view.findViewById(R.id.lat_text);
                holder.long_text = (TextView) view.findViewById(R.id.long_text);


                view.setTag(holder);
            } else {
                holder = (ViewHolder) view.getTag();
            }

            holder.title_text.setText(""+title.get(position));

            holder.des_text.setText(""+Html.fromHtml(start_time.get(position)));

            holder.lat_text.setText(""+Html.fromHtml(latitude.get(position)));

            holder.long_text.setText(""+Html.fromHtml(longitude.get(position)));

        return view;
        }
    }
}

Answer 1

ListView list = (ListView) findViewById(R.id.list);
title = new ArrayList<String>();
latitude = new ArrayList<String>();  
longitude = new ArrayList<String>();

希望你忘了ArrayList<String> start_time ;
所以，

ListView list = (ListView) findViewById(R.id.list);
title = new ArrayList<String>();
latitude = new ArrayList<String>();  
longitude = new ArrayList<String>(); 
start_time= new ArrayList<String>(); // <-- This Line