Программа не может добавить текст в JTextArea

Question

Я создал программу, которая создает графический интерфейс под названием Window() и инструктирует моего робота Finch следовать за объектом. Когда я запускаю программу, в JTextArea не добавляется текст. Он должен сказать, пожалуйста, коснитесь Finch для активации.

Моя программа рассказывает мне, что эта линия является источником ошибок:

NewOption5.feed.append("Please Tap Finch to Activate!");

консоли:

Подключение к Finch ... это может занять несколько секунд ...

Исключение в теме "main" java.lang.NullPointerException

at NewOption5.ProgramFollow (NewOption5.java:58)

в NewOption5.main (NewOption5.java:12)

Код:

import edu.cmu.ri.createlab.terk.robot.finch.Finch; 
import java.awt.*; 
import javax.swing.*; 

public class NewOption5 { 

    static JTextArea feed; 

    static Finch myFinch = new Finch(); 

public static void main(String[] args) { 
    //Calling Window  
// myFinch = new Finch(); 
    Window(); 
    ProgramFollow(); 



} 



// Method for creating a GUI 

//static Finch myFinch = new Finch(); 
public static void Window() 
    { 
    // Create the window 
    JFrame x = new JFrame("Finch Mission : Follow an Object!"); 

// How the window should be closed 
    x.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 

// Adding a layout manager 
    x.setLayout(new FlowLayout()); 

// Adding components (significantly a JTextArea being a feedback box) 
    x.add(new JButton("Halt!")); 
    x.add(new JButton("Exit")); 
    final JTextArea feed = new JTextArea(30,50); 
    JScrollPane feedscroll = new JScrollPane(feed); 
    x.add(feedscroll); 


// Arrange components neatly inside the window 
    x.pack(); 

// Making the window visible once Window is called 
    x.setVisible(true); 
// ProgramFollow(); 
} 





public static void ProgramFollow() { 

    // Loop to wait for Finch to be tapped and an obstacle detected in front of the Finch 
    boolean StartProgram; 
    NewOption5.feed.append("Please Tap Finch to Activate!");  

    while (StartProgram = true) 
    { 
    // Sending message to the feedback box 
    feed.append("Please Tap Finch to Activate!"); 

    // Conditional statement for same thing as mentioned above 

    if (myFinch.isTapped()==true && myFinch.isObstacleLeftSide()==true && myFinch.isObstacleRightSide()==true) 
    { 
    NewOption5.feed.append("Finch is activated! Object is detected"); 
    myFinch.setLED(red,0,0); 
    myFinch.setWheelVelocities(leftVelocity, rightVelocity); 

    // Triggers RunAgain to true so the program doesnt stop in one run in order for Finch to move continuosuly 


    boolean RunAgain=true; 




    while(RunAgain) 
    { 

    // Calling Movement method for Finch movements 

    Movement(); 

    // Inside while(RunAgain loop , there is a conditional statment which makes the Finch terminate the program after tapping it twice 

    if (myFinch.isTapped()==true && myFinch.isTapped()==true) 
    { 



    } 
    } 
    } 
    } 
    } 



    // Method for Finch movements 

    public static void Movement() 

    { 

    if (myFinch.isObstacleLeftSide()==false && myFinch.isObstacleRightSide()==false) 

    { 

    // send message to the feedback box ("Object is Detected! Following it now!"); 
    NewOption5.feed.append("Following the Object now!"); 

    StraightMovement(); 

    } 

    else if (myFinch.isObstacleLeftSide()==true && myFinch.isObstacleRightSide()==false) 

    { 

    NewOption5.feed.append("Object detected on the left side"); 

    LeftMovement(); 

    } 

    else if (myFinch.isObstacleLeftSide()==false && myFinch.isObstacleRightSide()==true) 

    { 

    NewOption5.feed.append("Object detected on the right side"); 

    RightMovement(); 

    } 

    else if (myFinch.isObstacleLeftSide()==true && myFinch.isObstacleRightSide()==true) 

    { 

    NewOption5.feed.append("Stopped now"); 

    StopMovement(); 

    } 

    } 


    // Area of variables declaration for easy value modifications 

    static int Buzz = 340; 
    static int BuzzDuration = 10; 


    static int red = 255; 
    static int green = 255; 

    static int leftVelocity = 100; 
    static int rightVelocity = 100; 

    static int leftTurnV = -50; 
    static int rightTurnV = -50;; 


    // Area of variables declaration for easy value modifications 


    public static void StraightMovement() 

    { 

    myFinch.setLED(0, green, 0); 

    myFinch.setWheelVelocities(leftVelocity, rightVelocity); 

    myFinch.buzz(Buzz, BuzzDuration); 

    } 

    public static void LeftMovement() 

    { 

    myFinch.setLED(0, green, 0); 

    myFinch.setWheelVelocities(leftTurnV, rightVelocity); 

    myFinch.buzz(Buzz, BuzzDuration); 

    } 

    public static void RightMovement() 

    { 

    myFinch.setLED(0, green, 0); 

    myFinch.setWheelVelocities(leftVelocity, rightTurnV); 

    myFinch.buzz(Buzz, BuzzDuration); 

    } 

    public static void StopMovement() 

    { 

    myFinch.setLED(red, 0 , 0); 

    myFinch.stopWheels(); 

    myFinch.buzz(Buzz, BuzzDuration); 

    } 


    } 

Answer 1

Вы не инициализировать feed правильно.

final JTextArea feed = new JTextArea(30,50); Это не инициализировать поле feed но вместо этого создает новую локальную переменную одного и того же имени.

Попробуйте поворачивать final JTextArea feed = new JTextArea(30,50); на feed = new JTextArea(30,50);.