这是我的代码.我正在尝试使用箭头键让球移动.当我运行上述程序时不显示球(如果我将坐标更改为显示 0,30 球)并且没有触发事件,球既不移动也不跳跃
This is my code.I am trying to make the ball move using arrow keys. As i run the above program ball is not displayed (if i change the coordinates to like 0,30 ball is displayed) and event is not fired ,ball neither moves nor jumps
什么问题
?
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class ControlledBall extends JPanel{
int diameter = 30;
int height = 30;
int x_Pos = 0;
int y_Pos;
ControlledBall() {
JFrame fr = new JFrame("Controlled Ball");
this.setBackground(Color.black);
fr.add(this);
fr.setVisible(true);
fr.setSize(600,400);
y_Pos = this.getHeight() - diameter ;
register();
repaint();
}
public void register() {
this.addKeyListener(new KeyAdapter() {
public void keyPressed(KeyEvent ke) {
if( ke.getKeyCode() == ke.VK_RIGHT ) {
increment();
}
else if( ke.getKeyCode() == ke.VK_LEFT ) {
decrement();
}
else if( ke.getKeyCode() == ke.VK_UP) {
jump();
}
}
});
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor( Color.blue );
g.fillOval( x_Pos , y_Pos , diameter , height );
System.out.println("testing...");
}
public void increment() {
x_Pos++;
if( x_Pos > (this.getWidth() - diameter) ) {
x_Pos = this.getWidth() - diameter;
}
repaint();
}
public void decrement() {
x_Pos--;
if( x_Pos <= 0) {
x_Pos = 0;
}
repaint();
}
public void jump() {
y_Pos++;
if( y_Pos <=0 ) {
y_Pos = 0;
}
repaint();
}
public static void main( String args[] ) {
new ControlledBall();
}
}
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class ControlledBall extends JPanel{
int diameter = 30;
int height = 30;
int x_Pos = 0;
int y_Pos;
ControlledBall() {
JFrame fr = new JFrame("Controlled Ball");
fr.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setBackground(Color.red);
setPreferredSize(new Dimension(400,300));
fr.add(this);
fr.setVisible(true);
// important!
fr.pack();
//fr.setSize(600,400);
y_Pos = this.getHeight()/2;
register();
repaint();
}
public void register() {
// very important!
setFocusable(true);
this.addKeyListener(new KeyAdapter() {
public void keyPressed(KeyEvent ke) {
if( ke.getKeyCode() == ke.VK_RIGHT ) {
increment();
}
else if( ke.getKeyCode() == ke.VK_LEFT ) {
decrement();
}
else if( ke.getKeyCode() == ke.VK_UP) {
jump();
}
}
});
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor( Color.orange );
g.fillOval( x_Pos , y_Pos , diameter , height );
}
public void increment() {
x_Pos++;
if( x_Pos > (this.getWidth() - diameter) ) {
x_Pos = this.getWidth() - diameter;
}
repaint();
}
public void decrement() {
x_Pos--;
if( x_Pos <= 0) {
x_Pos = 0;
}
repaint();
}
public void jump() {
y_Pos++;
if( y_Pos <=0 ) {
y_Pos = 0;
}
repaint();
}
public static void main( String args[] ) {
new ControlledBall();
}
}
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