actionPerformed 仅在计时器启动时运行

Question

Sup，希望你一切都好。出于某种原因，在我的 java 代码中，当我按下一个键时（虽然它有效），我的 ActionListener 要求我保持 Timer 启动，否则绘制矩形并显示 JLabel 简单的条件不会运行因为actionListener不能调用它。

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 计时器，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中时，具有响应事件而调用的回调方法在程序运行时发生的事件，例如仅在发生按键时调用的 KeyListeners。

ActionListeners也是如此。它们的代码仅在侦听器附加到事件生成器时被调用，并且该生成器生成事件。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 定时器，当定时器启动时，它会生成每 timer-delay 毫秒重复一次的事件，直到计时器停止。

您的代码的其他问题：

始终在您的重写中调用 super 的 paintComponent 方法。否则不会完成内务处理绘画，例如清除脏像素
永远不要删除 JVM 提供给您的 Graphics 对象，就像您正在做的那样，因为这会破坏绘画链。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(...) 方法来更改 JLabel 的可见性状态。该状态更改应进入计时器的 ActionListener 而不是绘画方法。

actionPerformed 仅在计时器启动时运行

actionPerformed only runs when a Timer starts

java

swing

timer

actionlistener

event-listener