Java用箭头键在gui中移动一个圆圈 [英] Java moving a circle in a gui with arrow keys

问题描述

我正在尝试使用keyEvent移动一个圆圈。到目前为止，圆圈是在窗口上绘制的，但它不会向左移动！我觉得问题是我将Window（）构造函数添加到容器的位置。控制台上没有输出告诉我它正在工作。所以我不认为它甚至到达KeyEvent类。这是我的代码：

I am trying to move a circle left with a keyEvent. So far, the circle is drawn on the window but it does not move left! I feel like the problem is where I add the Window() constructor to the container. The is no output on the console to tell me that it is working. So I dont think it even reaches the KeyEvent class. Here is my code:

import java.awt.*;
import java.awt.event.*;
import java.awt.geom.Ellipse2D;
import javax.swing.*;


public class Window extends JPanel {

    private static Ellipse2D.Double circle;

    public Window() {
        super();
        int width = 400;
        int height = 400;
        circle = new Ellipse2D.Double(0.5 * width, 0.9 * height,
                0.1 * width, 0.05 * height);
        addKeyListener(new MoveCircle());
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponents(g);
        Graphics2D brush = (Graphics2D) g;
        int width = getWidth();
        int height = getHeight();
        g.clearRect(0, 0, width, height);
        brush.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                RenderingHints.VALUE_ANTIALIAS_ON);
        brush.draw(circle);
    }

    public class MoveCircle implements KeyListener {

        @Override
        public void keyPressed(KeyEvent e) {
            System.out.println("Working on top!");
            if (e.getKeyCode() == KeyEvent.VK_LEFT) {
                System.out.println("Working on bottom!");
                circle.x++;
                repaint();
            }
        }

        @Override
        public void keyReleased(KeyEvent e) {
            // TODO Auto-generated method stub
        }

        @Override
        public void keyTyped(KeyEvent e) {
            // TODO Auto-generated method stub
        }
    }

    public static void main(String[] args) {
        Window window = new Window();
        JFrame frame = new JFrame();
        Container container = frame.getContentPane();
        container.add(new Window());
        frame.addKeyEvent(window.new MoveCircle());
        frame.setSize(800, 700);
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        frame.setVisible(true);
    }
}

推荐答案

实际上这是怎么回事，你要将 Window 添加到 JFrame ，但焦点在于 JFrame ，所以当您在键盘上键入时，该东西会转到 JFrame 不是附加到窗口类的 KeyListener 。所以为了克服它，你只需要在 Window 类的Object上调用 requestFocusInWindow（）。试试这段代码，我对EDT和东西做了一些修改。

Actually what is happening is this, you are adding Window to the JFrame, but the focus lies with the JFrame, so when you type on your Keyboard that thing goes to the JFrame not the KeyListener attached to the Window class. So in order to get over it, you simply have to call requestFocusInWindow() on the Window class's Object. Try this code, I had done some modification regarding EDT and stuff.

import java.awt.*;
import java.awt.event.*;
import java.awt.geom.Ellipse2D;
import javax.swing.*;


public class Window extends JPanel {

    private static Ellipse2D.Double circle;
    private JFrame frame;

    public Window() {
        super();
        int width = 400;
        int height = 400;
        circle = new Ellipse2D.Double(0.5 * width, 0.9 * height,
                0.1 * width, 0.05 * height);        
    }

    public Dimension getPreferredSize()
    {
        return (new Dimension(frame.getWidth(), frame.getHeight()));
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponents(g);
        Graphics2D brush = (Graphics2D) g;
        int width = getWidth();
        int height = getHeight();
        g.clearRect(0, 0, width, height);
        brush.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                RenderingHints.VALUE_ANTIALIAS_ON);
        brush.draw(circle);
    }

    public class MoveCircle implements KeyListener {

        @Override
        public void keyPressed(KeyEvent e) {
            System.out.println("Working on top!");
            if (e.getKeyCode() == Event.ENTER) {
                System.out.println("Working on bottom!");
                double newX = circle.x - 1;
                circle.x = newX;
                repaint();
            }
        }

        @Override
        public void keyReleased(KeyEvent e) {
            // TODO Auto-generated method stub
        }

        @Override
        public void keyTyped(KeyEvent e) {
            // TODO Auto-generated method stub
        }
    }

    private void createAndDisplayGUI(Window window)
    {
        frame = new JFrame();
        Container container = frame.getContentPane();       
        container.add(window);
        window.addKeyListener(new MoveCircle());        
        frame.setSize(800, 700);
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        frame.setVisible(true);
        window.requestFocusInWindow();
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable()
        {
            public void run()
            {
                Window window = new Window();
                window.createAndDisplayGUI(window);
            }
        });
    }
}

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