java - 调用绘制组件

Question

我正在尝试在 Java 中绘制对象，但在 TimerListener 类中遇到问题，它“无法解析符号 PaintComponent”(或符号 g)。我猜这很简单，但我似乎无法解决？

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


public class Beacon extends JPanel {
    private boolean choseOn = false;

   // Timer timer = new Timer(1000, onListener );

    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D) g;
        Rectangle box1 = new Rectangle(165, 75, 10, 25);
        g2.draw(box1);
        Rectangle box2 = new Rectangle(165, 100, 10, 25);
        g2.draw(box2);
        Rectangle box3 = new Rectangle(165, 125, 10, 25);
        g2.draw(box3);
        Rectangle box4 = new Rectangle(165, 150, 10, 25);
        g2.draw(box4);
        Rectangle box5 = new Rectangle(165, 175, 10, 25);
        g2.draw(box5);
        Rectangle box6 = new Rectangle(165, 200, 10, 25);
        g2.draw(box6);
        Rectangle box7 = new Rectangle(165, 225, 10, 25);
        g2.draw(box7);
        Rectangle box8 = new Rectangle(165, 250, 10, 25);
        g2.draw(box8);
        Rectangle box9 = new Rectangle(165, 275, 10, 25);
        g2.draw(box9);
        Rectangle box10 = new Rectangle(165, 300, 10, 25);
        g2.draw(box10);
        g2.setColor(Color.BLACK);
        g2.fill(box1);
        g2.fill(box3);
        g2.fill(box5);
        g2.fill(box7);
        g2.fill(box9);
        Ellipse2D.Double light = new Ellipse2D.Double(145, 26, 50, 50);
        if (choseOn) {
            //timer.setInitialDelay(1000);
            //timer.start();
            g2.setPaint(Color.GRAY);
            g2.fill(light);


        } else {
            g2.setColor(Color.ORANGE);
            g2.fill(light);
        }
    }
    public void chooseOn() { choseOn = false; }
    public void chooseOff() { choseOn = true; }

}

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


public class BeaconViewer extends JFrame {
    Timer timer;
    JButton off = new JButton("OFF");
    JButton on = new JButton("ON");
    JPanel panel1 = new JPanel();
    Beacon beaconPanel = new Beacon();

    public BeaconViewer() {
        panel1.add(off);
        panel1.add(on);
        this.add(panel1, BorderLayout.SOUTH);
        this.add(beaconPanel, BorderLayout.CENTER);
        //off.addActionListener(new offListener());
        //on.addActionListener(new onListener());

    }

    public static void main(String[] args) {
        JFrame beaconFrame = new BeaconViewer();
        beaconFrame.setTitle("Circle-Square");
        beaconFrame.setSize(350, 450);
        beaconFrame.setDefaultCloseOperation((JFrame.EXIT_ON_CLOSE));
        beaconFrame.setVisible(true);
    }

    class TimerListener implements ActionListener {
        public void actionPerformed(ActionEvent e) {

            Ellipse2D.Double light = new Ellipse2D.Double(145, 26, 50, 50);
            super.paintComponent(g);
            Graphics2D g2 = (Graphics2D) g;
            g2.setPaint(Color.ORANGE);
            g2.fill(light);
            repaint();
        }
    }


    //class offListener implements ActionListener {
      //  public void actionPerformed(ActionEvent e) {
        //    beaconPanel.chooseOff();
         //   repaint();
       // }
    //}
    //class onListener implements ActionListener {
      //  public void actionPerformed(ActionEvent e) {
        //    beaconPanel.chooseOn();
          //  repaint();
        //}
    }
//}

Answer 1

首先你不应该有像chooseOn()和chooseOff()这样的方法。相反，你应该这样做:

public void setChooseOn(boolean chooseOn)
{
    this.chooseOn = chooseOn;
    repaint();
}

public Boolean getChooseOn()
{
    return chooseOn;
}

也就是说，每当您想要更改类的属性时，您都应该为该属性提供一个 getter 和一个 setter。

I am having issues in the TimerListener class

您不能在监听器类中进行绘画。绘画仅在面板的paintComponent()方法中完成。

因此，Timer 监听器类中的代码将与 OffListener 和 OnListener 类中的代码类似。也就是说，您调用更改属性的方法。

因此，在您的情况下，代码可能如下所示:

beaconPanel.setChooseOn( ! beconPanel.getChooseOn() );

每次调用计时器时，此代码都会在 true/false 之间切换属性。无需调用 repaint()，因为 setChooseOn(...) 方法会为您完成此操作。