我已经搜索了几个类似标题的问题(例如how to use jpanel with paint (or repaint)),但我找不到我的代码不工作的原因。我是JPanels新手的图形,所以我第一次尝试这种事情就是制作一个可以用箭头键移动的三角形。我把三角形画得很好,没有问题。但是,当我试图用箭头移动三角形时,它没有移动。任何人都可以找到它为什么不重绘?JPanel repaint()不起作用
JPanel的代码(我也有对JFrame本身,这不仅使框架,并增加了面板的一个单独的类,如果你需要看,告诉我,我会在编辑):
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class Drawpanel extends JPanel implements KeyListener{
int[] xcoords = {-20,0,20};//Triangle x coordinates
int[] ycoords = {20,-20,20};//Triangle y coordinates
int x = 100;//X coordinate for drawing the triangle
int y = 100;//Y coordinate for drawing the triangle
Graphics2D g2d;
Polygon tri = new Polygon(xcoords,ycoords,xcoords.length);//triangle
public void paintComponent(Graphics g)
{
super.paintComponent(g);
g2d = (Graphics2D)g;
g2d.translate(x,y);//draw triangle at x and y coordinates
g2d.setColor(new Color(234,22,72));
g2d.fill(tri);
}
public void keyTyped(KeyEvent k){}
public void keyReleased(KeyEvent k){}
public void keyPressed(KeyEvent k)
{
int keycode = k.getKeyCode();
switch(keycode)
{
case KeyEvent.VK_DOWN://if down arrow pressed, decrease ship y coordinate by 10
y -= 10;
case KeyEvent.VK_UP:
y += 10;
case KeyEvent.VK_LEFT:
x -= 10;
case KeyEvent.VK_RIGHT:
x += 10;
}
repaint();//screen doesn't repaint
}
}
作为@camickr建议,看看[这里](http://stackoverflow.com/questions/22741215/how-to-use-key-bindings-instead-of-key-listeners)如何替换关键侦听器键绑定。 – user1803551