重绘图形问题 [英] Repainting Graphics Issue

问题描述

我一直在试着写一个小型的侧面卷轴游戏，但遇到了重绘（）而不重绘的问题。关键听众本身起作用，当方向键被按下时，它会递增和递减x和y值。

  public class SideScroller扩展了JPanel实现KeyListener {
 private随机随机=新随机（）; 
 private int r，g，b; 
 private int x = 0，y = 0; 
 $ b $ public void keyPressed（KeyEvent e）{
 if（e.getKeyCode（）== e.VK_UP）{
 y  -  = 5; 
} else if（e.getKeyCode（）== e.VK_DOWN）{
 y + = 5; 
} else if（e.getKeyCode（）== e.VK_LEFT）{
 x  -  = 5; 
} else if（e.getKeyCode（）== e.VK_RIGHT）{
 x + = 5; 
} 
 repaint（）; 
} 
 public void keyReleased（KeyEvent e）{} 
 public void keyTyped（KeyEvent e）{} 
 $ b $ public void paint（Graphics gg）{
 gg.setColor（new Color（r，g，b））; 
 gg.fillRect（x，y，50，50）; 
 
 
 public static void main（String [] args）{
 SideScroller ss = new SideScroller（）; 
 JFrame f = new JFrame（）; 
 
 f.add（new SideScroller（））; 
 f.setSize（500，500）; 
 f.setLocationRelativeTo（null）; 
 f.setResizable（false）; 
 f.setDefaultCloseOperation（JFrame.EXIT_ON_CLOSE）; 
 f.setVisible（true）; 
 f.addKeyListener（new SideScroller（））; 
 
  

解决方案

• 您应该重载 paintComponent 并调用 super.paintComponent ，而不是 paint 。

    protected void paintComponent（Graphics gg）{
   super.paintComponent（gg）; 
   gg.setColor（new Color（r，g，b））; 
   gg.fillRect（x，y，50，50）; 
  } 
    




• 另外我建议您使用键绑定而不是 KeyListener ，
  

• 你也可以在Event Dispacth Thread上运行Swing应用程序你可以通过将代码包装在 main

code> SwingUtilities.invokeLater（...）

下面是上面提到的所有修复程序：

  import java.awt.Color; 
 import java.awt.Graphics; 
 import java.awt.event.ActionEvent; 
 import java.util.Random; 
 import javax.swing.AbstractAction; 
 import javax.swing.ActionMap; 
 import javax.swing.InputMap; 
 import javax.swing.JComponent; 
 import javax.swing.JFrame; 
 import javax.swing.JPanel; 
 import javax.swing.KeyStroke; 
导入javax.swing.SwingUtilities; 
 
公共类SideScroller扩展JPanel {
 
 private随机random = new Random（）; 
 private int r，g，b; 
 private int x = 0，y = 0; 
 
 public SideScroller（）{
 InputMap im = getInputMap（JComponent.WHEN_IN_FOCUSED_WINDOW）; 
 ActionMap am = getActionMap（）; 
 im.put（KeyStroke.getKeyStroke（UP），upaction）; 
 am.put（upaction，new AbstractAction（）{
 public void actionPerformed（ActionEvent e）{
y  -  = 5; 
 
 repaint（）; 
} 
}）; 
 im.put（KeyStroke.getKeyStroke（DOWN），downact​​ion）; 
 am.put（downact​​ion，new AbstractAction（）{
 public void actionPerformed（ActionEvent e）{
y + = 5; 
 repaint（）; 
} 
}）; 
 im.put（KeyStroke.getKeyStroke（LEFT），leftaction）; 
 am.put（leftaction，new AbstractAction（）{
 public void actionPerformed（ActionEvent e）{
x  -  = 5; 
 repaint（）; 
} 
}）; 
 im.put（KeyStroke.getKeyStroke（RIGHT），rightaction）; 
 am.put（rightaction，new AbstractAction（）{
 public void actionPerformed（ActionEvent e）{
x + = 5; 
 repaint（）; 
} 
}）; 
} 
 
保护void paintComponent（Graphics gg）{
 super.paintComponent（gg）; 
 
 gg.setColor（new Color（r，g，b））; 
 gg.fillRect（x，y，50，50）; 
 
 
 public static void main（String [] args）{
 SwingUtilities.invokeLater（new Runnable（）{
 public void run（）{
）JFrame f = new JFrame（）; 
 
 f.add（new SideScroller（））; 
 f.setSize（500，500）; 
 f.setLocationRelativeTo（null） ; 
 f.setResizable（false）; 
 f.setDefaultCloseOperation（JFrame.EXIT_ON_CLOSE）; 
 f.setVisible（true）; 
} 
}）; 
} 
} 
  

I've been trying to write a small side-scroller game, but ran into an issue with repaint() not repainting. The key listener itself works, it increments and decrements the x and y values when the directional keys are pressed. Just the repaint() doesn't seem to be repainting.

public class SideScroller extends JPanel implements KeyListener{
private Random random = new Random();
private int r,g,b;
private int x = 0, y = 0;

public void keyPressed(KeyEvent e) {
    if(e.getKeyCode() == e.VK_UP) {
        y -= 5;
    } else if(e.getKeyCode() == e.VK_DOWN) {
        y += 5;
    } else if(e.getKeyCode() == e.VK_LEFT) {
        x -= 5;
    } else if(e.getKeyCode() == e.VK_RIGHT) {
        x += 5;
    }
    repaint();
}
public void keyReleased(KeyEvent e) {}
public void keyTyped(KeyEvent e) {}

public void paint(Graphics gg) {
    gg.setColor(new Color(r, g, b));
    gg.fillRect (x, y, 50, 50);
}

public static void main(String[] args) {
    SideScroller ss = new SideScroller();
    JFrame f = new JFrame();

    f.add(new SideScroller());
    f.setSize(500, 500);
    f.setLocationRelativeTo(null);
    f.setResizable(false);
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    f.setVisible(true);
    f.addKeyListener(new SideScroller());
}

解决方案

• You should be overriding paintComponent and calling super.paintComponent, not paint.

  protected void paintComponent(Graphics gg) {
      super.paintComponent(gg);
      gg.setColor(new Color(r, g, b));
      gg.fillRect (x, y, 50, 50);
  }
  

• Also I'd recommend looking into using Key Bindings instead of KeyListener,

• Also you should be running Swing apps on the Event Dispacth Thread You can d so by wrapping the code in the main in a SwingUtilities.invokeLater(...)

Here are all the fixes mentioned above

import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.util.Random;
import javax.swing.AbstractAction;
import javax.swing.ActionMap;
import javax.swing.InputMap;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.KeyStroke;
import javax.swing.SwingUtilities;

public class SideScroller extends JPanel {

    private Random random = new Random();
    private int r, g, b;
    private int x = 0, y = 0;

    public SideScroller() {
        InputMap im = getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW);
        ActionMap am = getActionMap();
        im.put(KeyStroke.getKeyStroke("UP"), "upaction");
        am.put("upaction", new AbstractAction() {
            public void actionPerformed(ActionEvent e) {
                y -= 5;

                repaint();
            }
        });
        im.put(KeyStroke.getKeyStroke("DOWN"), "downaction");
        am.put("downaction", new AbstractAction() {
            public void actionPerformed(ActionEvent e) {
                y += 5;
                repaint();
            }
        });
        im.put(KeyStroke.getKeyStroke("LEFT"), "leftaction");
        am.put("leftaction", new AbstractAction() {
            public void actionPerformed(ActionEvent e) {
                x -= 5;
                repaint();
            }
        });
        im.put(KeyStroke.getKeyStroke("RIGHT"), "rightaction");
        am.put("rightaction", new AbstractAction() {
            public void actionPerformed(ActionEvent e) {
                x += 5;
                repaint();
            }
        });
    }

    protected void paintComponent(Graphics gg) {
        super.paintComponent(gg);

        gg.setColor(new Color(r, g, b));
        gg.fillRect(x, y, 50, 50);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                JFrame f = new JFrame();

                f.add(new SideScroller());
                f.setSize(500, 500);
                f.setLocationRelativeTo(null);
                f.setResizable(false);
                f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                f.setVisible(true);
            }
        });
    }
}

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