Getting Null Pointer Exception in ListView Android

Question

I trying to use List View so show my date but i am getting exception .When i am running my application is is throwing the run time exception.Please suggest me what i have to do to get away from this execption : This is my Exception

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

Here is main class file

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);
    }
}

This is my OneWayResult Class Code

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;
    }
}

Answer 1

You are missing setContentView.

  protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState); // missing
  setContentView(R.layout.mylayout); // missing
      ...// rest of the code
  }

And you are trying to initialize your listview

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

You have not set the content to the activity. So if you try to initialize you will get NullPointerException.

You can findViewById of the current view hierarchy set to the activity.