android - ListView AndroidでNullポインタ例外を取得する

Question

リストビューを使用しようとしているので、日付を表示しますが、例外が発生します。アプリケーションを実行していると、実行時例外がスローされます。この例外から逃れるために何をしなければならないか教えてください:これは私の例外です

08-06 12:17:09.278: E/AndroidRuntime(3709): FATAL EXCEPTION: main
08-06 12:17:09.278: E/AndroidRuntime(3709): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.gridtestproject/com.example.gridtestproject.TestActivity}: java.lang.NullPointerException
08-06 12:17:09.278: E/AndroidRuntime(3709):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
08-06 12:17:09.278: E/AndroidRuntime(3709):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
08-06 12:17:09.278: E/AndroidRuntime(3709):     at android.app.ActivityThread.access$600(ActivityThread.java:141)
08-06 12:17:09.278: E/AndroidRuntime(3709):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
08-06 12:17:09.278: E/AndroidRuntime(3709):     at android.os.Handler.dispatchMessage(Handler.java:99)
08-06 12:17:09.278: E/AndroidRuntime(3709):     at android.os.Looper.loop(Looper.java:137)
08-06 12:17:09.278: E/AndroidRuntime(3709):     at android.app.ActivityThread.main(ActivityThread.java:5041)
08-06 12:17:09.278: E/AndroidRuntime(3709):     at java.lang.reflect.Method.invokeNative(Native Method)
08-06 12:17:09.278: E/AndroidRuntime(3709):     at java.lang.reflect.Method.invoke(Method.java:511)
08-06 12:17:09.278: E/AndroidRuntime(3709):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
08-06 12:17:09.278: E/AndroidRuntime(3709):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
08-06 12:17:09.278: E/AndroidRuntime(3709):     at dalvik.system.NativeStart.main(Native Method)
08-06 12:17:09.278: E/AndroidRuntime(3709): Caused by: java.lang.NullPointerException
08-06 12:17:09.278: E/AndroidRuntime(3709):     at com.example.gridtestproject.TestActivity.onCreate(TestActivity.java:47)
08-06 12:17:09.278: E/AndroidRuntime(3709):     at android.app.Activity.performCreate(Activity.java:5104)
08-06 12:17:09.278: E/AndroidRuntime(3709):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
08-06 12:17:09.278: E/AndroidRuntime(3709):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
08-06 12:17:09.278: E/AndroidRuntime(3709):     ... 11 more

ここにメインクラスファイルがあります

public class TestActivity extends Activity {

    ListView onewayListView,ReturnListView;
    OneWayFlightResult onewaydata;
    ReturnFlightResult returndata;
    static final String FlightNumber = ""; // parent node
    static final String FlightCompanyName = "";
    static final String FlightTime = "";
    static final String FlightStop ="";
    static final String FlightCost ="";

/** Called when the activity is first created. */

@Override
protected void onCreate(Bundle savedInstanceState) {
    ArrayList<HashMap<String, String>> flightData = new ArrayList<HashMap<String, String>>();
    for (int i = 0; i < 12; i++) {
        // creating new HashMap
        HashMap<String, String> map = new HashMap<String, String>();

        // adding each child node to HashMap key => value
        map.put(FlightCompanyName, "SpiceJet");
        map.put(FlightNumber, "SG-123");
        map.put(FlightTime, "6:00 - 7:00");
        map.put(FlightStop, "1h 30m | Non Stop");
        map.put(FlightCost, "Rs 20,000");

        // adding HashList to ArrayList
        flightData.add(map);
    }


    onewayListView=(ListView)findViewById(R.id.lvDepartures);
    ReturnListView=(ListView)findViewById(R.id.lvArrivals);

    // Getting adapter by passing xml data ArrayList
    onewaydata=new OneWayFlightResult(this, flightData);        
    onewayListView.setAdapter(onewaydata);

   // returndata=new ReturnFlightResult(this, flightData);        
   // onewayListView.setAdapter(returndata);
    }
}

これは私の OneWayResult クラスコードです

public class OneWayFlightResult extends BaseAdapter {

    private Activity activity;
    private ArrayList<HashMap<String, String>> data;
    private static LayoutInflater inflater=null;


    public OneWayFlightResult(Activity a, ArrayList<HashMap<String, String>> d) {
        activity = a;
        data=d;
        inflater = (LayoutInflater)activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);

    }

    @Override
    public int getCount() {
        // TODO Auto-generated method stub
        return data.size();
    }

    @Override
    public Object getItem(int position) {
        // TODO Auto-generated method stub
         return position;
    }

    @Override
    public long getItemId(int position) {
        // TODO Auto-generated method stub
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View vi=convertView;
        if(convertView==null)
            vi = inflater.inflate(R.layout.row, null);
        TextView flightTime = (TextView)vi.findViewById(R.id.flightTime); // title
        TextView flightCompanyName = (TextView)vi.findViewById(R.id.flightCompanyName); // title
        TextView flightNumber = (TextView)vi.findViewById(R.id.flightNumber); // title
        ImageView flightLogo = (ImageView)vi.findViewById(R.id.flightLogo);

        HashMap<String, String> flight = new HashMap<String, String>();
        flight = data.get(position);

        flightTime.setText(flight.get(TestActivity.FlightTime));
        flightCompanyName.setText(TestActivity.FlightCompanyName);
        flightNumber.setText(TestActivity.FlightNumber);
        return vi;
    }
}