actionPerformed僅在Timer啟動時運行-有解無憂

蘇，希望你一切都好。由于某種原因，在我的 java 代碼中，當我按下一個鍵時（雖然有效），我的 ActionListener 要求我保持計時器啟動，否則繪制一個矩形并顯示 JLabel 簡單的條件不會運行，因為 actionListener 可以'不叫它。

這是作業代碼。

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);
        }
    }
}

這就是導致 actionEvent 不執行的原因

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);
        }
    }
}

uj5u.com熱心網友回復：

您似乎在問為什么除非您打開 Swing Timer，否則永遠不會呼叫 ActionListener 中的代碼。

原因是，Swing 庫是一個事件驅動的 GUI 庫，并且該庫具有偵聽器類，當它們正確連接到您的代碼時，具有呼叫回呼方法以回應程式運行時發生的事件，例如作為僅在發生按鍵時呼叫的 KeyListener。

ActionListener 也是如此。僅當偵聽器連接到事件生成器并且該生成器生成事件時才呼叫它們的代碼。對于 ActionListener，事件生成器可以是 JButton（通過addActionListener），然后在按下 JButton 時呼叫偵聽器代碼，或者它可以附加到 Swing Timer，當 Timer 啟動時，這會生成一個重復每個事件的事件timer-delay 毫秒，直到計時器停止。

您的代碼的其他問題：

始終在您的覆寫中呼叫 super 的 paintComponent 方法。否則不做家務繪畫，比如清理臟像素
永遠不要洗掉 JVM 給你的 Graphics 物件，就像你正在做的那樣，因為這會破壞繪畫鏈。僅洗掉您自己創建的一個。
您的paintComponent 方法做得比它應該做的更多，因為它呼叫了paintDBG(...)改變JLabel 可見性狀態的方法。該狀態更改應該在計時器的 ActionListener 中而不是在繪畫方法中。

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