SimpleAdapter为空？

Question

package com.coltonnicotera.londontransitguide;

//bunch of imports

public class SchedulesActivity extends Activity {

    /** Called when the activity is first created. */
    List<Map<String, String>> routesList = new ArrayList<Map<String,String>>();

    String[] routesArray = new String[] {"01. Kipps Lane/Thompson Road", "02. Dundas", "03. Hamilton Rd", "04. Oxford East", "05. Springbank", "06. Richmond", "07. Wavell", "08. Riverside", "09. Whitehills", "10. Wonderland", "11. Southcrest", "12. Warncliffe South", "13. Wellington Road", "14. Highbury", "15. Westmount", "16. Adelaide", "17. Oxford West", "19. Oakridge", "20. Cherryhill", "21. Huron Heights", "22. Trafalgar", "23. Berkshire", "24. Baseline", "25. Kilally", "26. Jalna Blvd. West", "27. Fanshawe College", "28. Lambeth", "30. Newbold", "31. Orchard Park", "32. Windermere", "33. Proudfoot", "34. Medway", "35. Argyle", "36. Airport/Industrial", "37. Sovereign Road", "38. Stoney Creek", "39. Fanshawe West"};      

    public void onCreate(Bundle savedInstanceState) {
        initList();
        ListView lv = (ListView) findViewById(R.id.listView);    
        SimpleAdapter simpleAdpt = new SimpleAdapter(this, routesList, android.R.layout.simple_list_item_1, new String[] {"route"}, new int[] {android.R.id.text1}); 
/*LINE 63 */        lv.setAdapter(simpleAdpt);
    }

   private void initList() {
       for (int i = 0; i<=36; i++)
           routesList.add(createRoute("route", routesArray[i]));
    }

   private HashMap<String, String> createRoute(String key, String name) {
        HashMap<String, String> route = new HashMap<String, String>();
        route.put(key, name);
        return route;
    }
}

我的问题是在第63行有一个NullPointerException。我不确定这里到底什么是null。为了简单起见，我删除了所有的导入。R.id.listView也存在。

Answer 1

您还没有设置为什么listview findViewbyId返回null...so的布局您需要在oncreate()中设置contentView，然后再实际获取listview ...like setContentView(R.layout.yourlayout)