JApplet创建了一个在Java中反弹并逐渐降低的球 [英] JApplet creates a ball that bounces and gets progressively less high in Java
问题描述
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);
}
}
所以我想创造一个反弹的球然后逐渐变小。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。
So I am trying to create a ball that bounces up and down and progressively gets smaller. I need to use the following code as a class that will set up my next class that will actually carry out the action. I know that I need to set up the current code that I have into constructors, instance variables and methods to create objects from but I can't seem to figure out how to do that.
另外，如何让绘制的图像在JApplet上上下移动？
Also how would I make the drawn image move up and down across the JApplet?
推荐答案
这是一个基本的例子这个想法
This is a basic example of the idea
基本上，当你按空格键时，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，然后它会下降并反弹直到它已经用尽了反弹
Basically, when you press the spacebar, it generates a vertical movement which slows over time till it runs out of energy, it will then fall and rebound until it has run out of "bounce"
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<的概念a href =http://docs.oracle.com/javase/tutorial/uiswing/misc/keybinding.html =nofollow noreferrer>键绑定， Swing Timer 和基本的自定义绘画
The example introduces concepts of Key Bindings, Swing Timer and basic custom painting
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