Javadrone-连接到无人机后如何获取无人机信息？ EG电池电量，海拔高度等？

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.