首先，我强烈建议您不要使用KeyListener，这是最好的麻烦，更好的选择是使用Key Bindings API，它是为了修复KeyListener API的短整数而设计的。第二，你不应该修改多边形的点，2D图形API实际上可以有一些非常巧妙的技巧，这使得它更容易和更快地改变你的位置（以及旋转和缩放）正在绘制。
查看更多细节请看2D Graphics。
而是改变多，这是不考虑可视范围的点，你可以简单地用一个AffineTransform ...
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
Point location = frog.getLocation();
AffineTransform at = AffineTransform.getTranslateInstance(location.x, location.y);
g2d.transform(at);
g2d.setColor(new Color(0, 150, 15));
g2d.fill(frog);
g2d.setColor(Color.BLACK);
g2d.draw(frog);
g2d.dispose();
}
这只是简单地改变了Graphics的原点上下文要绘制多边形的位置（是的，还有另外一个原因，我使用的是AffineTransform
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.Polygon;
import java.awt.Rectangle;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.geom.AffineTransform;
import javax.swing.AbstractAction;
import javax.swing.Action;
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 Test {
public static void main(String[] args) {
new Test();
}
public Test() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new Board());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
protected enum VerticalDirection {
NONE, UP, DOWN;
}
protected enum HorizontalDirection {
NONE, LEFT, RIGHT;
}
public static class Board extends JPanel {
protected static final int Y_DELTA = 4;
protected static final int X_DELTA = 4;
private Frog frog;
private VerticalDirection verticalDirection = VerticalDirection.NONE;
private HorizontalDirection horizontalDirection = HorizontalDirection.NONE;
public Board() {
setBackground(Color.GREEN);
frog = new Frog();
Timer timer = new Timer(40, new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
Point location = frog.getLocation();
switch (verticalDirection) {
case UP:
location.y -= Y_DELTA;
break;
case DOWN:
location.y += Y_DELTA;
break;
}
switch (horizontalDirection) {
case LEFT:
location.x -= X_DELTA;
break;
case RIGHT:
location.x += X_DELTA;
break;
}
Rectangle bounds = frog.getBounds();
int width = bounds.x + bounds.width;
int height = bounds.y + bounds.height;
if (location.y < 0) {
location.y = 0;
} else if (location.y + height > getHeight()) {
location.y = getHeight() - height;
}
if (location.x < 0) {
location.x = 0;
} else if (location.x + width > getWidth()) {
location.x = getWidth() - width;
}
frog.setLocation(location);
repaint();
}
});
timer.start();
addPressedKeyBinding("up", KeyEvent.VK_UP, new VerticalMovementAction(VerticalDirection.UP));
addPressedKeyBinding("down", KeyEvent.VK_DOWN, new VerticalMovementAction(VerticalDirection.DOWN));
addPressedKeyBinding("left", KeyEvent.VK_LEFT, new HorizontalMovementAction(HorizontalDirection.LEFT));
addPressedKeyBinding("right", KeyEvent.VK_RIGHT, new HorizontalMovementAction(HorizontalDirection.RIGHT));
addReleasedKeyBinding("up", KeyEvent.VK_UP, new VerticalMovementAction(VerticalDirection.NONE));
addReleasedKeyBinding("down", KeyEvent.VK_DOWN, new VerticalMovementAction(VerticalDirection.NONE));
addReleasedKeyBinding("left", KeyEvent.VK_LEFT, new HorizontalMovementAction(HorizontalDirection.NONE));
addReleasedKeyBinding("right", KeyEvent.VK_RIGHT, new HorizontalMovementAction(HorizontalDirection.NONE));
}
protected void addPressedKeyBinding(String name, int virtuaKey, Action action) {
addKeyBinding(name + ".pressed", KeyStroke.getKeyStroke(virtuaKey, 0, false), action);
}
protected void addReleasedKeyBinding(String name, int virtuaKey, Action action) {
addKeyBinding(name + ".released", KeyStroke.getKeyStroke(virtuaKey, 0, true), action);
}
protected void addKeyBinding(String name, KeyStroke ks, Action action) {
InputMap im = getInputMap(WHEN_IN_FOCUSED_WINDOW);
ActionMap am = getActionMap();
im.put(ks, name);
am.put(name, action);
}
@Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
Point location = frog.getLocation();
AffineTransform at = AffineTransform.getTranslateInstance(location.x, location.y);
g2d.transform(at);
g2d.setColor(new Color(0, 150, 15));
g2d.fill(frog);
g2d.setColor(Color.BLACK);
g2d.draw(frog);
g2d.dispose();
}
protected class VerticalMovementAction extends AbstractAction {
private VerticalDirection direction;
public VerticalMovementAction(VerticalDirection direction) {
this.direction = direction;
}
@Override
public void actionPerformed(ActionEvent e) {
verticalDirection = direction;
}
}
protected class HorizontalMovementAction extends AbstractAction {
private HorizontalDirection direction;
public HorizontalMovementAction(HorizontalDirection direction) {
this.direction = direction;
}
@Override
public void actionPerformed(ActionEvent e) {
horizontalDirection = direction;
}
}
}
public static class Frog extends Polygon {
private Integer[] xcoord;
private Integer[] ycoord;
private Point location;
public Frog() {
location = new Point(0, 0);
xcoord = new Integer[]{5, 10, 10, 15, 15, 20,
20, 30, 30, 35, 35, 40, 40,
45, 45, 40, 40, 30, 30, 40,
40, 45, 45, 40, 40, 35, 35,
30, 30, 20, 20, 15, 15, 10,
10, 5, 5, 10, 10, 20, 20,
10, 10, 5, 5};
ycoord = new Integer[]{10, 10, 5, 5, 20, 20,
10, 10, 20, 20, 5, 5, 10, 10,
15, 15, 25, 25, 30, 30, 35, 35,
40, 40, 45, 45, 35, 35, 40, 40,
35, 35, 45, 45, 40, 40, 35, 35,
30, 30, 25, 25, 15, 15, 10};
for (int i = 0; i < xcoord.length; i++) {
this.addPoint(xcoord[i], ycoord[i]);
}
}
public Point getLocation() {
return location;
}
public void setLocation(Point location) {
this.location = location;
}
}
}
现在，你可能想知道为什么我会用AffineTransform，而不是Graphcis2D#translate，最主要的原因是，它很容易申请其他转换，如旋转......
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
Point location = frog.getLocation();
Rectangle bounds = frog.getBounds();
int width = bounds.x + bounds.width;
int height = bounds.y + bounds.height;
AffineTransform at = AffineTransform.getTranslateInstance(location.x, location.y);
at.rotate(Math.toRadians(angle), width/2, height/2);
g2d.transform(at);
g2d.setColor(new Color(0, 150, 15));
g2d.fill(frog);
g2d.setColor(Color.BLACK);
g2d.draw(frog);
g2d.dispose();
}
这样做只是申请一个复合转换，移动Graphics上下文的起源和旋转矩阵
而对于一个完整的例子...
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.Polygon;
import java.awt.Rectangle;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.geom.AffineTransform;
import javax.swing.AbstractAction;
import javax.swing.Action;
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 Test {
public static void main(String[] args) {
new Test();
}
public Test() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new Board());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
protected enum VerticalDirection {
NONE, UP, DOWN;
}
protected enum HorizontalDirection {
NONE, LEFT, RIGHT;
}
public static class Board extends JPanel {
protected static final int Y_DELTA = 4;
protected static final int X_DELTA = 4;
private Frog frog;
private VerticalDirection verticalDirection = VerticalDirection.NONE;
private HorizontalDirection horizontalDirection = HorizontalDirection.NONE;
private double angle = 0; // Up...
public Board() {
setBackground(Color.GREEN);
frog = new Frog();
Timer timer = new Timer(40, new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
Point location = frog.getLocation();
switch (verticalDirection) {
case UP:
angle = 0;
location.y -= Y_DELTA;
break;
case DOWN:
angle = 180;
location.y += Y_DELTA;
break;
}
switch (horizontalDirection) {
case LEFT:
location.x -= X_DELTA;
angle = 270;
break;
case RIGHT:
location.x += X_DELTA;
angle = 90;
break;
}
Rectangle bounds = frog.getBounds();
int width = bounds.x + bounds.width;
int height = bounds.y + bounds.height;
if (location.y < 0) {
location.y = 0;
} else if (location.y + height > getHeight()) {
location.y = getHeight() - height;
}
if (location.x < 0) {
location.x = 0;
} else if (location.x + width > getWidth()) {
location.x = getWidth() - width;
}
frog.setLocation(location);
repaint();
}
});
timer.start();
addPressedKeyBinding("up", KeyEvent.VK_UP, new VerticalMovementAction(VerticalDirection.UP));
addPressedKeyBinding("down", KeyEvent.VK_DOWN, new VerticalMovementAction(VerticalDirection.DOWN));
addPressedKeyBinding("left", KeyEvent.VK_LEFT, new HorizontalMovementAction(HorizontalDirection.LEFT));
addPressedKeyBinding("right", KeyEvent.VK_RIGHT, new HorizontalMovementAction(HorizontalDirection.RIGHT));
addReleasedKeyBinding("up", KeyEvent.VK_UP, new VerticalMovementAction(VerticalDirection.NONE));
addReleasedKeyBinding("down", KeyEvent.VK_DOWN, new VerticalMovementAction(VerticalDirection.NONE));
addReleasedKeyBinding("left", KeyEvent.VK_LEFT, new HorizontalMovementAction(HorizontalDirection.NONE));
addReleasedKeyBinding("right", KeyEvent.VK_RIGHT, new HorizontalMovementAction(HorizontalDirection.NONE));
}
protected void addPressedKeyBinding(String name, int virtuaKey, Action action) {
addKeyBinding(name + ".pressed", KeyStroke.getKeyStroke(virtuaKey, 0, false), action);
}
protected void addReleasedKeyBinding(String name, int virtuaKey, Action action) {
addKeyBinding(name + ".released", KeyStroke.getKeyStroke(virtuaKey, 0, true), action);
}
protected void addKeyBinding(String name, KeyStroke ks, Action action) {
InputMap im = getInputMap(WHEN_IN_FOCUSED_WINDOW);
ActionMap am = getActionMap();
im.put(ks, name);
am.put(name, action);
}
@Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
Point location = frog.getLocation();
Rectangle bounds = frog.getBounds();
int width = bounds.x + bounds.width;
int height = bounds.y + bounds.height;
AffineTransform at = AffineTransform.getTranslateInstance(location.x, location.y);
at.rotate(Math.toRadians(angle), width/2, height/2);
g2d.transform(at);
g2d.setColor(new Color(0, 150, 15));
g2d.fill(frog);
g2d.setColor(Color.BLACK);
g2d.draw(frog);
g2d.dispose();
}
protected class VerticalMovementAction extends AbstractAction {
private VerticalDirection direction;
public VerticalMovementAction(VerticalDirection direction) {
this.direction = direction;
}
@Override
public void actionPerformed(ActionEvent e) {
verticalDirection = direction;
}
}
protected class HorizontalMovementAction extends AbstractAction {
private HorizontalDirection direction;
public HorizontalMovementAction(HorizontalDirection direction) {
this.direction = direction;
}
@Override
public void actionPerformed(ActionEvent e) {
horizontalDirection = direction;
}
}
}
public static class Frog extends Polygon {
private Integer[] xcoord;
private Integer[] ycoord;
private Point location;
public Frog() {
location = new Point(0, 0);
xcoord = new Integer[]{5, 10, 10, 15, 15, 20,
20, 30, 30, 35, 35, 40, 40,
45, 45, 40, 40, 30, 30, 40,
40, 45, 45, 40, 40, 35, 35,
30, 30, 20, 20, 15, 15, 10,
10, 5, 5, 10, 10, 20, 20,
10, 10, 5, 5};
ycoord = new Integer[]{10, 10, 5, 5, 20, 20,
10, 10, 20, 20, 5, 5, 10, 10,
15, 15, 25, 25, 30, 30, 35, 35,
40, 40, 45, 45, 35, 35, 40, 40,
35, 35, 45, 45, 40, 40, 35, 35,
30, 30, 25, 25, 15, 15, 10};
// I rest the coordinates back to 0x0 because it's easier to
// deal with when applying a rotation...
for (int index = 0; index < xcoord.length; index++) {
xcoord[index] -= 5;
}
for (int index = 0; index < ycoord.length; index++) {
ycoord[index] -= 5;
}
for (int i = 0; i < xcoord.length; i++) {
this.addPoint(xcoord[i], ycoord[i]);
}
}
public Point getLocation() {
return location;
}
public void setLocation(Point location) {
this.location = location;
}
}
}
看，不用数学！
我真是个傻瓜......我知道这会是一件简单的事情。我实现了这种变化，现在它与翻译方法完美地结合在一起。非常感谢你的帮助！ – ineverfinishanyth
@ineverfinishanyth很高兴帮助你:) – Paul