Javadrone - How to get the drone info after connected into drone? E.G. Battery level, Altitude etc?

Question

I am working on an application to control Parrot Ar.Drone using Javadrone API & its libraries. I am able to connect into drone & make it take off/land successfully.

Javadrone API can be download here : https://code.google.com/p/javadrone/downloads/list

However, I have no idea how to extract out drone's info that I wanted. I was trying to call the appropriate function. But it can't works.

My code:

import com.codeminders.ardrone.NavData;

In my class : -
    //declare a jlabel for battery level 
    public NavData data;
    public int value = data.getBattery();
    JLabel batteryStatus = new JLabel(); 

    batteryStatus.setForeground(Color.YELLOW);    
    batteryStatus.setText(data.getBattery()+ " %");

    if (value < 15) {
            batteryStatus.setForeground(Color.RED);
    } else if (value < 50) {
            batteryStatus.setForeground(Color.ORANGE);
    } else {
            batteryStatus.setForeground(Color.GREEN);
    }

Any idea how to make it works ? If I run this snippet of code, it won't run since it will compilation stucks at getBattery() method. I wanted to implement this calling function in project so that relevant flight info. such as altitude can be shown on my apps. Thanks.

The output of code compilation:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at ardrone.arDroneFrame.jButtonConnectActionPerformed(arDroneFrame.java:462)
LINE 462 : batteryStatus.setText(data.getBattery()+ " %");

Answer 1

You need to use the com.codeminders.ardrone.NavDataListener interface.

1. Implement the NavDataListener interface, and the navDataReceived method.
2. Add your listener using the ARDrone method addNavDataListener.
3. In your navDataRecieved method you will receive a NavData object with valid telemetry data.