所以我有一个应用程序,可以根据按下键盘上的哪个按钮成功地向左、向右、向上或向下移动球(椭圆)。然而,我很难让球以一定角度移动。我试图通过说如果用户按住 2 个方向键,球将沿对角线进入。例如,如果他们单击向左键和向上键,我希望球向西北方向移动。如果你们中有人知道导致问题的原因,我将非常感谢您的帮助!
引擎
class KeyClickListener implements KeyListener
{
public void keyPressed(KeyEvent e)
{
if (e.getKeyCode() == KeyEvent.VK_DOWN )
{
component.moveCircle(1);
}
else if (e.getKeyCode() == KeyEvent.VK_UP)
{
component.moveCircle(2);
}
else if (e.getKeyCode() == KeyEvent.VK_RIGHT)
{
component.moveCircle(3);
}
else if (e.getKeyCode() == KeyEvent.VK_LEFT)
{
component.moveCircle(5);
}
//this is my attempt at telling whether or not the user was holding two keys
else if (e.getKeyCode() == KeyEvent.VK_LEFT && e.getKeyCode() == KeyEvent.VK_UP)
{
component.moveCircle(5);
}
}
public void keyReleased(KeyEvent e){}
public void keyTyped(KeyEvent e){}
}
圆形组件
public void moveCircle(int w)
{
dir = w;
if (dir == 1)
{
y+=20;
repaint();
if (y>=560)
{
dir=2;
}
}
.
.
.
else if (dir == 5)
{
x-=10;
y-=10;
repaint();
if(x<=0 )
{
dir=3;
}
}
}
最佳答案
由于按键事件只会报告触发该事件的最后一个按键,因此您的最后一个 if
语句将永远不会起作用,因为 keyCode
只会等于最后一个按键触发了该事件。
相反,您应该维护每个键的“状态”并针对该状态进行处理。
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class TestKeyListener01 {
public static void main(String[] args) {
new TestKeyListener01();
}
public TestKeyListener01() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
private boolean arrowUp = false;
private boolean arrowDown = false;
private boolean arrowLeft = false;
private boolean arrowRight = false;
public TestPane() {
setFocusable(true);
addKeyListener(new KeyAdapter() {
@Override
public void keyReleased(KeyEvent e) {
switch (e.getKeyCode()) {
case KeyEvent.VK_DOWN:
arrowDown = false;
break;
case KeyEvent.VK_UP:
arrowUp = false;
break;
case KeyEvent.VK_LEFT:
arrowLeft = false;
break;
case KeyEvent.VK_RIGHT:
arrowRight = false;
break;
}
repaint();
}
@Override
public void keyPressed(KeyEvent e) {
switch (e.getKeyCode()) {
case KeyEvent.VK_DOWN:
arrowDown = true;
break;
case KeyEvent.VK_UP:
arrowUp = true;
break;
case KeyEvent.VK_LEFT:
arrowLeft = true;
break;
case KeyEvent.VK_RIGHT:
arrowRight = true;
break;
}
repaint();
}
});
}
@Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
FontMetrics fm = g2d.getFontMetrics();
String text = "Up";
int x = (getWidth() - fm.stringWidth(text)) / 2;
int y = ((getHeight() / 2) - fm.getHeight());
draw(g2d, text, x, y, arrowUp);
text = "Down";
x = (getWidth() - fm.stringWidth(text)) / 2;
y = ((getHeight() / 2) + fm.getHeight()) + fm.getAscent();
draw(g2d, text, x, y, arrowDown);
text = "Left";
x = (getWidth() / 2) - fm.stringWidth(text) - 4;
y = ((getHeight() - fm.getHeight()) / 2) + fm.getAscent();
draw(g2d, text, x, y, arrowLeft);
text = "Right";
x = (getWidth() / 2) + 4;
y = ((getHeight() - fm.getHeight()) / 2) + fm.getAscent();
draw(g2d, text, x, y, arrowRight);
g2d.dispose();
}
protected void draw(Graphics2D g2d, String text, int x, int y, boolean pressed) {
g2d.setColor(pressed ? Color.BLACK : Color.GRAY);
g2d.drawString(text, x, y);
}
}
}
我还建议您应该使用 Key Bindings 而不是 KeyListener
反而。它们解决了困扰 KeyListener
关于java - 在java中使用键盘以角度移动圆,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/16290543/