Netbeans中的Java :如何用角度移动球

Question

我目前正在用Java开发游戏，但我对球的移动有困难，因为我想让球在接触球员和砖块时改变它的角度。下面是我到目前为止开发的代码：

public class BrickGame extends javax.swing.JFrame {

boolean GameOver = false;
boolean ballMovingUp = false;
boolean ballMovingLeft = false;


Thread ballmvng = new Thread() {
    public void run() {
        while (true) {
            ball.setLocation(ball.getX() + (ballMovingLeft ? -1 : 1), ball.getY() + (ballMovingUp ? -1 : 1));
            try {
                Thread.sleep(10);
            } catch (Exception e) {
            }
            if (ball.getX() < 0) {
                ballMovingLeft = false;
            }
            if (ball.getX() + ball.getWidth() > 350) {
                ballMovingLeft = true;
            }
            if (intersects(ball, player)) {
                ballMovingUp = true;
            }
            if (intersects(ball, OrangeBrick1)) {
                ballMovingUp = false;
                OrangeBrick1.setVisible(false);
                int currentScore = Integer.parseInt(score.getText());
                currentScore = currentScore + 1;
                score.setText(""+currentScore);  
            }
            if (intersects(ball, OrangeBrick2)) {
                ballMovingUp = false;
                OrangeBrick2.setVisible(false);
                int currentScore = Integer.parseInt(score.getText());
                currentScore = currentScore + 1;
                score.setText(""+currentScore);  
            }
            if (intersects(ball, OrangeBrick3)) {
                ballMovingUp = false;
                OrangeBrick3.setVisible(false);
                int currentScore = Integer.parseInt(score.getText());
                currentScore = currentScore + 1;
                score.setText(""+currentScore);  
            }
            if (intersects(ball, OrangeBrick4)) {
                ballMovingUp = false;
                OrangeBrick4.setVisible(false);
                int currentScore = Integer.parseInt(score.getText());
                currentScore = currentScore + 1;
                score.setText(""+currentScore);  
            }
            if (intersects(ball, OrangeBrick5)) {
                ballMovingUp = false;
                OrangeBrick5.setVisible(false);
                int currentScore = Integer.parseInt(score.getText());
                currentScore = currentScore + 1;
                score.setText(""+currentScore);  
            }
            if (intersects(ball, OrangeBrick6)) {
                ballMovingUp = false;
                OrangeBrick6.setVisible(false);
                int currentScore = Integer.parseInt(score.getText());
                currentScore = currentScore + 1;
                score.setText(""+currentScore);  
            }
            if (intersects(ball, YellowBrick1)) {
                ballMovingUp = false;
                YellowBrick1.setVisible(false);
                int currentScore = Integer.parseInt(score.getText());
                currentScore = currentScore + 1;
                score.setText(""+currentScore);  
            }
            if (intersects(ball, YellowBrick2)) {
                ballMovingUp = false;
                YellowBrick2.setVisible(false);
                int currentScore = Integer.parseInt(score.getText());
                currentScore = currentScore + 1;
                score.setText(""+currentScore);  
            }
            if (intersects(ball, YellowBrick3)) {
                ballMovingUp = false;
                YellowBrick3.setVisible(false);
                int currentScore = Integer.parseInt(score.getText());
                currentScore = currentScore + 1;
                score.setText(""+currentScore);  
            }
             if (intersects(ball, YellowBrick4)) {
                ballMovingUp = false;
                YellowBrick4.setVisible(false);
                int currentScore = Integer.parseInt(score.getText());
                currentScore = currentScore + 1;
                score.setText(""+currentScore);  
            }
            if (intersects(ball, YellowBrick5)) {
                ballMovingUp = false;
                YellowBrick5.setVisible(false);
                int currentScore = Integer.parseInt(score.getText());
                currentScore = currentScore + 1;
                score.setText(""+currentScore);  
            }
            if (intersects(ball, YellowBrick6)) {
                ballMovingUp = false;
                YellowBrick6.setVisible(false);
                int currentScore = Integer.parseInt(score.getText());
                currentScore = currentScore + 1;
                score.setText(""+currentScore);  
            }
            if (intersects(ball, RedBrick1)) {
                ballMovingUp = false;
                RedBrick1.setVisible(false);
                int currentScore = Integer.parseInt(score.getText());
                currentScore = currentScore + 1;
                score.setText(""+currentScore);  
            }
            if (intersects(ball, RedBrick2)) {
                ballMovingUp = false;
                RedBrick2.setVisible(false);
                int currentScore = Integer.parseInt(score.getText());
                currentScore = currentScore + 1;
                score.setText(""+currentScore);  
            }
            if (intersects(ball, RedBrick3)) {
                ballMovingUp = false;
                RedBrick3.setVisible(false);
                int currentScore = Integer.parseInt(score.getText());
                currentScore = currentScore + 1;
                score.setText(""+currentScore);  
            }
            if (intersects(ball, RedBrick4)) {
                ballMovingUp = false;
                RedBrick4.setVisible(false);
                int currentScore = Integer.parseInt(score.getText());
                currentScore = currentScore + 1;
                score.setText(""+currentScore);  
            }
            if (intersects(ball, PurpleBrick1)) {
                ballMovingUp = false;
                PurpleBrick1.setVisible(false);
                int currentScore = Integer.parseInt(score.getText());
                currentScore = currentScore + 1;
                score.setText(""+currentScore);  
            }
            if (intersects(ball, PurpleBrick2)) {
                ballMovingUp = false;
                PurpleBrick2.setVisible(false);
                int currentScore = Integer.parseInt(score.getText());
                currentScore = currentScore + 1;
                score.setText(""+currentScore);  
            }
            if (ball.getY() < 0) {
                ballMovingUp = false;
            }
            if (ball.getY() + ball.getHeight() > 405) {
                GameOver = true;
                return;
            }
            
        }
    }
};

public BrickGame() {
    initComponents();

    ballmvng.start();
}
      public static void main(String args[]) {
      public void run() {
      new BrickGame().setVisible(true);
        }
    }
}

Answer 1

这是一个弹跳球的简单例子。

Ball类使用极坐标来保持球的方向和速度。极坐标转换为笛卡尔坐标，以便在绘图JPanel上绘制球。

calculateNewPosition方法计算球的新位置。正如你所看到的，我所要做的就是改变球的方向，改变角度。在笛卡尔坐标计算之前，角度保持为度，并转换为弧度。

其余代码使用Swing Timer来控制动画。

这是完整的可运行代码。我在内部创建了额外的类，这样我就可以将代码作为一个块发布。

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.geom.Point2D;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.Timer;

public class BallExample implements Runnable {

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new BallExample());
    }
    
    private final BallExampleModel model;
    
    private final DrawingPanel drawingPanel;
    
    public BallExample() {
        this.model = new BallExampleModel();
        this.drawingPanel = new DrawingPanel(model);
    }

    @Override
    public void run() {
        JFrame frame = new JFrame("Ball Example");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        
        frame.add(drawingPanel, BorderLayout.CENTER);
        
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
        
        Timer timer = new Timer(30, new BallMotionListener(this, model));
        timer.start();
    }
    
    public void repaint() {
        drawingPanel.repaint();
    }
    
    public class DrawingPanel extends JPanel {

        private static final long serialVersionUID = 1L;
        
        private final BallExampleModel model;
        
        public DrawingPanel(BallExampleModel model) {
            this.model = model;
            this.setPreferredSize(model.getDrawingPanelDimension());
        }
        
        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            
            Ball ball = model.getBall();
            Point2D point = ball.getPosition();
            int x = (int) Math.round(point.getX());
            int y = (int) Math.round(point.getY());
            int radius = ball.getRadius();
            int diameter = radius + radius;
            
            g.setColor(Color.BLUE);
            g.fillOval(x - radius, y - radius, diameter, diameter);
        }
        
    }
    
    public class BallMotionListener implements ActionListener {
        
        private final BallExample view;
        
        private final BallExampleModel model;

        public BallMotionListener(BallExample view, BallExampleModel model) {
            this.view = view;
            this.model = model;
        }

        @Override
        public void actionPerformed(ActionEvent event) {
            model.getBall().calculateNewPosition();
            view.repaint();
        }
        
    }
    
    public class BallExampleModel {
        
        private final Ball ball;
        
        private final Dimension drawingPanelDimension;
        
        public BallExampleModel() {
            this.drawingPanelDimension = new Dimension(400, 400);
            this.ball = new Ball(8, 325, drawingPanelDimension);
        }

        public Ball getBall() {
            return ball;
        }

        public Dimension getDrawingPanelDimension() {
            return drawingPanelDimension;
        }
        
    }
    
    public class Ball {
        
        private double xPosition, yPosition;
        
        private int angle, radius, speed;
        
        private final Dimension drawingPanelDimension;

        public Ball(int speed, int angle, Dimension drawingPanelDimension) {
            this.speed = speed;
            this.radius = 12;
            this.angle = angle;
            this.drawingPanelDimension = drawingPanelDimension;
            this.xPosition = drawingPanelDimension.width / 2;
            this.yPosition = drawingPanelDimension.height / 2;
        }

        public int getAngle() {
            return angle;
        }

        public void setAngle(int angle) {
            this.angle = angle;
        }

        public int getSpeed() {
            return speed;
        }

        public void setSpeed(int speed) {
            this.speed = speed;
        }
        
        public int getRadius() {
            return radius;
        }
        
        public void calculateNewPosition() {
            double theta = Math.toRadians(angle);
            double xDifference = Math.cos(theta) * speed;
            double yDifference = Math.sin(theta) * speed;
            xPosition += xDifference;
            yPosition += yDifference;
            
            if (xPosition < radius) {
                angle = 540 - angle;
            }
            
            if (xPosition > drawingPanelDimension.width - radius) {
                angle = 540 - angle;
            }
            
            if (yPosition < radius) {
                angle = 360 - angle;
            }
            
            if (yPosition > drawingPanelDimension.height - radius) {
                angle = 360 - angle;
            }
            
            angle %= 360;
        }

        public Point2D getPosition() {
            return new Point2D.Double(xPosition, yPosition);
        }
        
    }

}