我对Java的经验有限，尤其是与图形有关的经验。到目前为止，我已经在这个问题上提供了很大的帮助。它是入门代码（在底部），在我在Eclipse中对其进行测试时，它可以正常工作。我正在上课时用它来教一名高中生。按照下面注释中的说明，有人会知道一种简单的方法来扩展已经很简单的程序，从而在按下Z按钮之后使球跳/移动/重绘到随机的新位置吗？我正在考虑将以下代码添加到keyPressed（KeyEvent e）方法中：
else if(keyCode == KeyEvent.VK_Z)
{
//Not sure what to add here. Just want to change X and Y coordinates to
//anything, so long as the program works and stays fairly simple
//for now.
//----> g.fillOval(x + radius, y + radius, 2 * radius, 2 * radius);
// this line above says "g can not be resolved".
}
。
任何使程序简单的技巧或想法将不胜感激。谢谢！
。
import java.awt.*;
import java.awt.event.*; // #1
import javax.swing.*;
/******************************************************************************
*
* KeyListenerDemo.java
* Demonstrates getting keyboard input using the KeyListener interface.
*
* Program 18: Extend this program by adding a few more keystroke commands:
* z (VK_Z) - Cause the ball to jump to a random new location.
* s (VK_S) - Make the ball smaller - multiply its diameter 1/2.
* b (VK_B) - Make the ball bigger - multiply its diameter by 2.
* c (VK_C) - Change the color (in any way you'd like).
*
* In addition, modify the program to ensure the following:
* - The ball goes all the way to the edge of the screen but stays
* completely on the screen.
* - If a doubled diameter doesn't fit, make it as large as possible.
* - Be sure the ball never completely disappears.
*
*****************************************************************************/
public class KeyListenerDemo extends JFrame
implements KeyListener // #2
{
// Class Scope Finals
private static final int SCREEN_WIDTH = 1000;
private static final int SCREEN_HEIGHT = 800;
private static final int START_RADIUS = 25;
private static final int START_X = 100;
private static final int START_Y = 100;
private static final int STEP_SIZE = 10;
// Class Scope Variables
private static int x = START_X; // x at center of the ball
private static int y = START_Y; // y at center of the ball
private static int radius = START_RADIUS; // radius of the ball
// Methods
/**
* Create the window and register this as a KeyListener
*
* @param args
*/
public static void main (String[] args)
{
// Set up the JFrame window.
KeyListenerDemo gp = new KeyListenerDemo();
gp.setSize(SCREEN_WIDTH, SCREEN_HEIGHT);
gp.setVisible(true);
gp.addKeyListener(gp); // #3
// If this class had a constructor and you moved this line into
// that constructor it could not refer to gp since that variable
// is local to this method. Instead you would write::
// addKeyListener(this);
}
/**
* Called when a key is first pressed
* Required for any KeyListener
*
* @param e Contains info about the key pressed
*/
public void keyPressed(KeyEvent e) // #4A
{
int keyCode = e.getKeyCode();
if (keyCode == KeyEvent.VK_LEFT)
{
x = x - STEP_SIZE;
}
else if (keyCode == KeyEvent.VK_RIGHT)
{
x = x + STEP_SIZE;
}
else if (keyCode == KeyEvent.VK_UP)
{
y = y - STEP_SIZE;
}
else if (keyCode == KeyEvent.VK_DOWN)
{
y = y + STEP_SIZE;
}
repaint();
}
/**
* Called when typing of a key is completed
* Required for any KeyListener
*
* @param e Contains info about the key typed
*/
public void keyTyped(KeyEvent e) // #4B
{
}
/**
* Called when a key is released
* Required for any KeyListener
*
* @param e Contains info about the key released
*/
public void keyReleased(KeyEvent e) // #4C
{
}
/**
* paint - draw the figure
*
* @param g Graphics object to draw in
*/
public void paint(Graphics g)
{
g.setColor(Color.white);
g.fillRect(0, 0, SCREEN_WIDTH, SCREEN_HEIGHT);
g.setColor(Color.blue);
g.fillOval(x - radius, y - radius, 2 * radius, 2 * radius);
}
}
最佳答案
尝试做这样的事情：
public void keyPressed(KeyEvent e){
if(e.getKeyCode == KeyEvent.VK_Z){
moveRand();
//Assuming that is the method for moving the ball randomly.
}
}
然后
public void moveRand(Graphics2D g){
g.drawOval(Random.nextInt() / window.getWidth() + 1, Random.nextInt() / window.getHight() + 1, ballWidth, ballHight);
}
希望这会有所帮助。