我的代码不会清除之前的矩形。我认为通过使用 getRect() ,然后在 keyPressed() 方法中使用 repaint() ,就可以解决问题。
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.KeyEvent;
import java.awt.geom.Rectangle2D;
import javax.swing.Icon;
import java.awt.*;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.geom.AffineTransform;
import java.awt.geom.Arc2D;
import java.awt.geom.PathIterator;
import java.awt.geom.Point2D;
import java.awt.geom.Rectangle2D;
import java.util.ArrayList;
import javax.swing.Icon;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
public class Rectangle extends JFrame implements KeyListener{
private int height;
private int width;
private int x;
private int y;
private Graphics2D g2;
public Rectangle(int width, int height,int x, int y)
{
this.height = height;
this.width = width;
this.x = x;
this.y = y;
JLabel label = new JLabel();
setSize(1000,1000);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLocationRelativeTo(null);
setVisible(true);
label.addKeyListener(this);
label.setFocusable(true);
label.setOpaque(true);
label.addKeyListener(this);
this.add(label);
setVisible(true);
label.requestFocusInWindow();
}
public void keyPressed(KeyEvent e)
{
if (e.getKeyCode() == KeyEvent.VK_DOWN)
{
g2.clearRect(x, y, width, height);
repaint();
y = y + 5;
repaint();
}
if (e.getKeyCode() == KeyEvent.VK_LEFT)
{
g2.clearRect(x, y, width, height);
repaint();
x = x - 5;
repaint();
}
if (e.getKeyCode() == KeyEvent.VK_UP)
{
g2.clearRect(x, y, width, height);
repaint();
y = y - 5;
repaint();
}
if (e.getKeyCode() == KeyEvent.VK_RIGHT)
{
g2.clearRect(x, y, width, height);
x = x + 5;
repaint();
}
}
public void keyReleased(KeyEvent e) {}
public void keyTyped(KeyEvent e) {}
public void paint(Graphics g) {
g2 = (Graphics2D) g;
g2.drawRect(x, y, width, height);
}
}
测试方法:
public class Test {
public static void main(String[] args)
{
Rectangle rectangle = new Rectangle(400,200,500,500);
}
}
最佳答案
setVisible(true)
应该是 publicRectangle(...
) 中的最后一个代码行,因为您将JComponent
添加到已经可见的 Swing GUI。默认情况下,
JFrame
对于KeyEvent
无法获得焦点。将
JPanel
放到JFrame
的CENTER
区域,默认:myFrame.add(myPanel)
.覆盖
JPanel
的getPreferredSize
,而不是设置JFrame
大小;应通过调用 myFrame.pack() 来初始化大小。JPanel
必须可聚焦才能接收KeyEvent
、setFocusable(true)
;使用 KeyBindings 而不是在JComponent
层次结构中寻找焦点。覆盖
JPanel
的paintComponent
;第一个代码行应该是super.paintComponent
,否则会出现绘画伪像。
关于java - 按下按键后绘制的对象不会清除先前的矩形,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/23480130/