actionPerformed仅在计时器启动时运行

Question

Sup，希望你们都没事。由于某种原因，在我的java代码中，当我按下一个键时(当它工作时(，ActionListener要求我保持计时器启动，否则绘制矩形并显示JLabel simple的条件不会运行，因为ActionListener无法调用它。

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);
}
}
}

以下是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，该库具有侦听器类，这些侦听器类在正确连接到代码中时，具有回调方法，这些方法是在程序运行时响应发生的事件而调用的，例如只有在按键发生时才调用的KeyListener。

ActionListeners也是如此。只有当侦听器连接到事件生成器，并且该生成器生成事件时，才会调用它们的代码。对于ActionListener，事件生成器可能是一个JButton(通过addActionListener(，然后当按下JButton时调用侦听器代码，或者它可以连接到Swing Timer，当Timer启动时，它会生成一个事件，每个定时器延迟毫秒重复一次，直到定时器停止。

代码的其他问题：

• 始终在覆盖中调用super的paintComponent方法。否则，不进行内务喷漆，例如清洁脏像素
• 永远不要删除JVM给你的Graphics对象，就像你正在做的那样，因为这会破坏绘画链。只删除您自己创建的一个
• 您的paintComponent方法做得比它应该做的更多，因为它调用了paintDBG(...)方法，该方法更改了JLabel的可见性状态。状态更改应该在计时器的ActionListener中进行，而不是在绘制方法中