我正在尝试用java为移动球程序编写简单的代码。我是java新手，我的意思是我知道基础知识，所以这是我的代码，以防你可以帮助我。我无法移动球对象。我创建了具有 gui 组件的类框架以及具有 he ball 功能的 ball 类
public class Frame extends JFrame{
private static final int width= 500;
private static final int height=500;
private static final Color cbw= Color.BLACK;
private Ball ball; // the moving object
private DrawCanvas canvas; // the custom drawing canvas
private JPanel btnpanel; // the panel of the buttons
private JPanel mainpanel; // the mainpanel
private JButton button_ML; // move_Left button
private JButton button_MR;// move_Right button
public Frame (){
setProperties();
init();
setUI();
}
private void setProperties() {
setSize(width, height);
setTitle("MOVE THE BALL");
setDefaultCloseOperation(EXIT_ON_CLOSE);
setLocationRelativeTo(null);
}
private void init(){
btnpanel = new JPanel(new FlowLayout());
mainpanel= new JPanel(new BorderLayout());
button_ML = new JButton("Move left");
button_MR = new JButton("Move right");
//creating the ball with its features
ball= new Ball (30,30,width/2-2,height/2-10,Color.red);
canvas = new DrawCanvas();
// it makes possible the ball to be seen though we have a main panel.
canvas.setPreferredSize(new Dimension(width,height));
button_ML.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent ae) {
move_Left();
}
});
button_MR.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent ae) {
move_Right();
}
});
}
private void setUI(){
mainpanel.add(btnpanel, BorderLayout.SOUTH);// adds the button panels to the main panel
btnpanel.add(button_ML);// adds the button to the panel of buttons
btnpanel.add(button_MR);
mainpanel.add(canvas, BorderLayout.CENTER); // adds the canvas to mainpanel
add(mainpanel); // adds the panel in the frame
}
class DrawCanvas extends JPanel {
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
setBackground(cbw); // puts color to the background
ball.paint(g); // the ball paints itself
}
}
private void move_Left(){
int savedX = ball.x;
ball.x -=10;
canvas.repaint(savedX, ball.y, ball.WIDTH, ball.HEIGHT);
canvas.repaint(ball.x,ball.y,ball.WIDTH,ball.HEIGHT);
}
private void move_Right(){
int savedX = ball.x;
ball.x += 10;
canvas.repaint(savedX, ball.y, ball.WIDTH, ball.HEIGHT);
canvas.repaint(ball.x,ball.y,ball.WIDTH,ball.HEIGHT);
}
}
//球类
public class Ball extends JFrame {
//variables for the construction of the circle
int x, y; // actual position of the ball
int WIDTH, HEIGHT;// parameters for the size of the rectangle where the circle is posited.
Color color = Color.RED;// the color of the ball
// the constructor of the class
public Ball(int x, int y, int WIDTH, int HEIGHT,Color color) {
this.x = x;//
this.y = y;
this.WIDTH = WIDTH;
this.HEIGHT = HEIGHT;
this.color=color;
}
// method for the color and drawing the ball
public void paint(Graphics g) {
g.setColor(Color.red);
g.fillOval(80,70, 350,350);
}
}
最佳答案
首先在 paint 方法中使用 Ball 的值而不是:
// method for the color and drawing the ball
public void paint(Graphics g) {
g.setColor(Color.red);
g.fillOval(80,70, 350,350);
}
它应该看起来像
// method for the color and drawing the ball
public void paint(Graphics g) {
g.setColor(Color.red);
g.fillOval(x,y, WIDTH, HEIGHT);
}
关于java - 无法在java中移动对象，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/47072249/