actionPerformed 仅在 Timer 启动时运行

Question

Sup，希望你们一切都好。由于某种原因，在我的 java 代码中，当我按下一个键时（虽然有效），我的 ActionListener 要求我保持计时器启动，否则绘制一个矩形并显示 JLabel 简单的条件不会运行，因为 actionListener 可以'不叫它。

这是工作代码。

package Game;

import javax.swing.JPanel;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import java.awt.event.KeyAdapter;
import java.awt.Color;
import java.awt.Toolkit;
import java.awt.Dimension;
import javax.swing.ImageIcon;
import java.awt.Image;
import java.awt.Point;
import java.awt.Graphics;
import java.awt.Graphics2D;
import javax.swing.JLabel;
import java.awt.Font;
import java.awt.Rectangle;
import javax.swing.Timer;

public class Riven extends JPanel implements ActionListener
{
    private keyBindings kb;
    private int C_ImageID = 0;
    private Dimension size = Toolkit.getDefaultToolkit().getScreenSize(); //Get screen resolution
    private Image C_Image;
    JLabel mouseX = new JLabel();
    private final int DELAY = 10;
    private Timer timer;

    public Riven()
    {
        initRiven();
    }

    private void initRiven()
    {
        addKeyListener(new TAdapter());
        setBackground(Color.black);
        loadImage();
        setFocusable(true);

        kb = new keyBindings(); //set keyBindings

        //Configuring the Debug JLabel
        mouseX.setFont(new java.awt.Font("Microsoft YaHei UI", Font.PLAIN, 16)); //Set configurations such as Font, and size
        mouseX.setText("Test");
        mouseX.setOpaque(false);
        mouseX.setForeground(Color.white);
        add(mouseX);

        setLayout(null);
        mouseX.setBounds(new Rectangle(new Point(200, 300), mouseX.getPreferredSize()));
        mouseX.setLocation(mouseX.WIDTH + 10, 10);
        mouseX.setVisible(false);

        timer = new Timer(DELAY, this);
        timer.start();
    }

    private void loadImage()
    {
        String imagedir = showImage.importImage(C_ImageID, size);
        ImageIcon ii = new ImageIcon(imagedir);
        C_Image = ii.getImage();
    }

    //Paints
    @Override
    public void paintComponent(Graphics g)
    {
        g.drawImage(C_Image, 0, 0, null); //Draw the front frame
        paintDBG(g);
    }

    private void paintDBG(Graphics g)
    {
        Graphics2D g2d = (Graphics2D) g;

        if (kb.getDBG()) //If the debug is set to ON
        {
            //set shape color
            g2d.setPaint(Color.black);

            //drawing the rectangle
            g2d.fillRect(0, 0, size.width / 10 , size.height / 10);
            mouseX.setVisible(true);
        }
        else
        {
            g2d.dispose();
            mouseX.setVisible(false);
        }
    }

    @Override
    public void actionPerformed(ActionEvent e)
    {
        repaint();
    }
    
    //Key Bindings
    private class TAdapter extends KeyAdapter
    {
        @Override
        public void keyPressed(KeyEvent e)
        {
            System.out.print("Entrei");
            kb.keyPressed(e);
        }

        @Override
        public void keyReleased(KeyEvent e)
        {
            System.out.print("Sai");
            kb.keyReleased(e);
        }
    }
}

这就是导致 actionEvent 不执行的原因

package Game;

import javax.swing.JPanel;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import java.awt.event.KeyAdapter;
import java.awt.Color;
import java.awt.Toolkit;
import java.awt.Dimension;
import javax.swing.ImageIcon;
import java.awt.Image;
import java.awt.Point;
import java.awt.Graphics;
import java.awt.Graphics2D;
import javax.swing.JLabel;
import java.awt.Font;
import java.awt.Rectangle;
import javax.swing.Timer;

public class Riven extends JPanel implements ActionListener
{
    private keyBindings kb;
    private int C_ImageID = 0;
    private Dimension size = Toolkit.getDefaultToolkit().getScreenSize(); //Get screen resolution
    private Image C_Image;
    JLabel mouseX = new JLabel();
    private final int DELAY = 10;
    private Timer timer;

    public Riven()
    {
        initRiven();
    }

    private void initRiven()
    {
        addKeyListener(new TAdapter());
        setBackground(Color.black);
        loadImage();
        setFocusable(true);

        kb = new keyBindings(); //set keyBindings

        //Configuring the Debug JLabel
        mouseX.setFont(new java.awt.Font("Microsoft YaHei UI", Font.PLAIN, 16)); //Set configurations such as Font, and size
        mouseX.setText("Test");
        mouseX.setOpaque(false);
        mouseX.setForeground(Color.white);
        add(mouseX);

        setLayout(null);
        mouseX.setBounds(new Rectangle(new Point(200, 300), mouseX.getPreferredSize()));
        mouseX.setLocation(mouseX.WIDTH + 10, 10);
        mouseX.setVisible(false);

        //timer = new Timer(DELAY, this);
        //timer.start();
    }

    private void loadImage()
    {
        String imagedir = showImage.importImage(C_ImageID, size);
        ImageIcon ii = new ImageIcon(imagedir);
        C_Image = ii.getImage();
    }

    //Paints
    @Override
    public void paintComponent(Graphics g)
    {
        g.drawImage(C_Image, 0, 0, null); //Draw the front frame
        paintDBG(g);
    }

    private void paintDBG(Graphics g)
    {
        Graphics2D g2d = (Graphics2D) g;

        if (kb.getDBG()) //If the debug is set to ON
        {
            //set shape color
            g2d.setPaint(Color.black);

            //drawing the rectangle
            g2d.fillRect(0, 0, size.width / 10 , size.height / 10);
            mouseX.setVisible(true);
        }
        else
        {
            g2d.dispose();
            mouseX.setVisible(false);
        }
    }

    @Override
    public void actionPerformed(ActionEvent e)
    {
        repaint();
    }
    
    //Key Bindings
    private class TAdapter extends KeyAdapter
    {
        @Override
        public void keyPressed(KeyEvent e)
        {
            System.out.print("Entrei");
            kb.keyPressed(e);
        }

        @Override
        public void keyReleased(KeyEvent e)
        {
            System.out.print("Sai");
            kb.keyReleased(e);
        }
    }
}

Answer 1

您似乎在问为什么除非您打开 Swing Timer，否则永远不会调用 ActionListener 中的代码。

原因是，Swing 库是一个事件驱动的 GUI 库，并且该库具有侦听器类，当正确连接到您的代码时，具有回调方法，这些回调方法被调用以响应程序运行时发生的事件运行，例如仅在按键发生时调用的 KeyListeners。

对于 ActionListener 也是如此。仅当侦听器连接到事件生成器并且该生成器生成事件时才调用它们的代码。对于 ActionListener，事件生成器可以是 JButton（通过addActionListener），然后在按下 JButton 时调用侦听器代码，或者它可以附加到 Swing Timer，当 Timer 启动时，它会生成一个事件重复每个 timer-delay 毫秒，直到计时器停止。

您的代码的其他问题：

• 始终在您的覆盖中调用 super 的 paintComponent 方法。否则不会进行内务处理，例如清理脏像素
• 永远不要删除 JVM 提供给您的 Graphics 对象，就像您正在做的那样，因为这会破坏绘制链。只删除您自己创建的一个。
• 您的paintComponent 方法做的比它应该做的更多，因为它调用paintDBG(...) 方法来改变JLabel 的可见性状态。该状态更改应该在计时器的 ActionListener 中进行，而不是在绘画方法中。