JApplet创建了一个在Java中反弹并逐渐降低的球

public class Circle extends JApplet { public void paint(Graphics g) { int x=100; int y=100; int diameter=50; int xResize=500; int yResize=500; super.paint(g); resize(xResize,yResize); g.drawOval(x, y, diameter, diameter); } } 

所以我试图创造一个上下反弹并逐渐变小的球。 我需要使用以下代码作为一个类来设置我将实际执行操作的下一个类。 我知道我需要将当前的代码设置为构造函数，实例变量和创建对象的方法，但我似乎无法弄清楚如何做到这一点。

另外，我如何使绘制的图像在JApplet上上下移动？

Answer 1

这是这个想法的基本例子

基本上，当你按下空格键时，它会产生一个垂直运动，随着时间的推移逐渐减慢，直到它耗尽能量，它会下降并反弹，直到它没有“反弹”

 import java.awt.BorderLayout; import java.awt.Dimension; import java.awt.EventQueue; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.event.KeyEvent; import javax.swing.AbstractAction; import javax.swing.ActionMap; import javax.swing.InputMap; import javax.swing.JFrame; import javax.swing.JPanel; import javax.swing.KeyStroke; import javax.swing.Timer; import javax.swing.UIManager; import javax.swing.UnsupportedLookAndFeelException; public class JumpingSprite { public static void main(String[] args) { new JumpingSprite(); } public JumpingSprite() { EventQueue.invokeLater(new Runnable() { @Override public void run() { try { UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName()); } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) { } JFrame frame = new JFrame("Test"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setLayout(new BorderLayout()); frame.add(new TestPane()); frame.pack(); frame.setLocationRelativeTo(null); frame.setVisible(true); } }); } public static class TestPane extends JPanel { protected static final int SPRITE_HEIGHT = 10; protected static final int SPRITE_WIDTH = 10; private float vDelta; // The vertical detla... private float rbDelta; // Rebound delta... private float rbDegDelta; // The amount the rebound is degregated... private int yPos; // The vertical position... private float gDelta; // Gravity, how much the vDelta will be reduced by over time... private Timer engine; private boolean bounce = false; public TestPane() { yPos = getPreferredSize().height - SPRITE_HEIGHT; vDelta = 0; gDelta = 0.25f; // This is how much the re-bound will degrade on each cycle... rbDegDelta = 2.5f; InputMap im = getInputMap(WHEN_IN_FOCUSED_WINDOW); ActionMap am = getActionMap(); im.put(KeyStroke.getKeyStroke(KeyEvent.VK_SPACE, 0), "jump"); am.put("jump", new AbstractAction() { @Override public void actionPerformed(ActionEvent e) { // Can only bound when we're actually on the ground... // You might want to add fudge factor here so that the // sprite can be within a given number of pixels in order to // jump again... if (yPos + SPRITE_HEIGHT == getHeight()) { vDelta = -8; rbDelta = vDelta; bounce = true; } } }); engine = new Timer(40, new ActionListener() { @Override public void actionPerformed(ActionEvent e) { int height = getHeight(); // No point if we've not been sized... if (height > 0) { // Are we bouncing... if (bounce) { // Add the vDelta to the yPos // vDelta may be postive or negative, allowing // for both up and down movement... yPos += vDelta; // Add the gravity to the vDelta, this will slow down // the upward movement and speed up the downward movement... // You may wish to place a max speed to this vDelta += gDelta; // If the sprite is not on the ground... if (yPos + SPRITE_HEIGHT >= height) { // Seat the sprite on the ground yPos = height - SPRITE_HEIGHT; // If the re-bound delta is 0 or more then we've stopped // bouncing... if (rbDelta >= 0) { // Stop bouncing... bounce = false; } else { // Add the re-bound degregation delta to the re-bound delta rbDelta += rbDegDelta; // Set the vDelta... vDelta = rbDelta; } } } } repaint(); } }); engine.start(); } @Override public Dimension getPreferredSize() { return new Dimension(200, 200); } @Override protected void paintComponent(Graphics g) { super.paintComponent(g); Graphics2D g2d = (Graphics2D) g.create(); int width = getWidth() - 1; int xPos = (width - SPRITE_WIDTH) / 2; g2d.drawOval(xPos, yPos, SPRITE_WIDTH, SPRITE_HEIGHT); g2d.dispose(); } } } 

该示例介绍了键绑定 ， Swing Timer和基本自定义绘制的概念