我正在尝试创建一个使用包含特定形状（圆形，方形，椭圆形，矩形）的JComboBox的程序。用户单击指定的形状后，Panel将以随机尺寸和位置显示该形状的20个。
我在如何使形状具有随机尺寸和位置方面遇到麻烦。到目前为止，这是我的代码。任何建议或来源，将不胜感激。
谢谢。
import javax.swing.*;
import java.awt.*;
import java.awt.geom.*;
import java.util.*;
import java.awt.event.*;
public class HW1b extends JFrame
{
public HW1b()
{
super("Shapes");
final ComboPanel comboPanel = new ComboPanel();
String[] shapeItems = {"Circle", "Square", "Oval", "Rectangle"};
JComboBox shapeBox = new JComboBox<String>(shapeItems);
shapeBox.addItemListener(new ItemListener()
{
public void itemStateChanged(ItemEvent ie)
{
if (ie.getStateChange() == ItemEvent.SELECTED)
{
String item = (String)ie.getItem();
if(shapeBox.getSelectedItem().equals("Circle"))
comboPanel.makeCircles();
if(shapeBox.getSelectedItem().equals("Square"))
comboPanel.makeSquares();
if(shapeBox.getSelectedItem().equals("Oval"))
comboPanel.makeOvals();
if(shapeBox.getSelectedItem().equals("Rectangle"))
comboPanel.makeRectangles();
}
}
});
JPanel southPanel = new JPanel();
southPanel.add(shapeBox);
setDefaultCloseOperation(EXIT_ON_CLOSE);
getContentPane().add(comboPanel, "Center");
getContentPane().add(southPanel, "South");
setSize( 400, 400 );
setLocation( 200, 200 );
setVisible( true );
}
private class ComboPanel extends JPanel
{
int w, h;
Random rand;
static final int OVAL = 0;
static final int RECTANGLE = 1;
int shapeType = -1;
public ComboPanel()
{
rand = new Random();
setBackground(Color.white);
}
public void paintComponent(Graphics g)
{
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
int width = getWidth();
int height = getHeight();
int x, y;
Shape s = null;
for (int i = 0; i < 20; i++)
{
x = rand.nextInt(width - w);
y = rand.nextInt(width - h);
switch(shapeType)
{
case OVAL: s = new Ellipse2D.Double(x,y,w,h);
break;
case RECTANGLE: s = new Rectangle2D.Double(x,y,w,h);
break;
}
if (shapeType > -1)
g2d.draw(s);
}
}
public void makeCircles()
{
shapeType = OVAL;
w = 75;
h = 75;
repaint();
}
public void makeSquares()
{
shapeType = RECTANGLE;
w = 50;
h = 50;
repaint();
}
public void makeOvals()
{
shapeType = OVAL;
w = 80;
h = 60;
repaint();
}
public void makeRectangles()
{
shapeType = RECTANGLE;
w = 80;
h = 40;
repaint();
}
}
public static void main(String[] args)
{
new HW1b();
}
}
答案 0 :(得分：4)
您在代码中对w和h进行了硬编码，因此您的形状无法改变。不要这样做，而是使用随机变量rand来选择在某个所需范围内的随机w和h值。我自己，我不会在paintComponent方法中创建我的形状，因为绘画不完全在我的控制之下，并且可以在我不想要的时候发生。例如，在代码中，如果调整GUI大小，您的形状会有很大差异。相反，我会创建一个集合，例如ArrayList<Shape>，并在需要时用创建的Shape对象（即我的圆圈的Ellipse2D）填充它，然后在paintComponent方法中迭代遍历该集合，绘制形状。
例如......
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.Shape;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import java.awt.geom.Ellipse2D;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import javax.swing.*;
public class SomeShapes extends JPanel {
private ShapePanel shapePanel = new ShapePanel();
private JComboBox<MyShape> myShapeCombo = new JComboBox<>(MyShape.values());
public SomeShapes() {
myShapeCombo.setSelectedIndex(-1);
myShapeCombo.addItemListener(new ComboListener());
JPanel bottomPanel = new JPanel();
bottomPanel.add(myShapeCombo);
setLayout(new BorderLayout());
add(shapePanel, BorderLayout.CENTER);
add(bottomPanel, BorderLayout.PAGE_END);
}
private class ComboListener implements ItemListener {
@Override
public void itemStateChanged(ItemEvent e) {
MyShape myShape = (MyShape) e.getItem();
shapePanel.drawShapes(myShape);
}
}
private static void createAndShowGui() {
JFrame frame = new JFrame("SomeShapes");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(new SomeShapes());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}
enum MyShape {
OVAL("Oval"), RECTANGLE("Rectangle"), SQUARE("Square"), CIRCLE("Circle");
private String name;
private MyShape(String name) {
this.name = name;
}
public String getName() {
return name;
}
@Override
public String toString() {
return getName();
}
}
class ShapePanel extends JPanel {
private static final int PREF_W = 600;
private static final int PREF_H = PREF_W;
private static final Color SHAPE_COLOR = Color.BLUE;
private static final int SHAPE_COUNT = 20;
private static int MIN = 5;
private static int MAX = 200;
private List<Shape> shapeList = new ArrayList<>();
private Random random = new Random();
@Override
public Dimension getPreferredSize() {
if (isPreferredSizeSet()) {
return super.getPreferredSize();
}
return new Dimension(PREF_W, PREF_H);
}
public void drawShapes(MyShape myShape) {
shapeList.clear(); // empty the shapeList
switch (myShape) {
case OVAL:
drawOval();
break;
case RECTANGLE:
drawRectangle();
break;
// etc...
default:
break;
}
repaint();
}
private void drawOval() {
// for loop to do this times SHAPE_COUNT(20) times.
for (int i = 0; i < SHAPE_COUNT; i++) {
// first create random width and height
int w = random.nextInt(MAX - MIN) + MIN;
int h = random.nextInt(MAX - MIN) + MIN;
// then random location, but taking care so that it
// fully fits into our JPanel
int x = random.nextInt(getWidth() - w);
int y = random.nextInt(getHeight() - h);
// then create new Shape and place in our shapeList.
shapeList.add(new Ellipse2D.Double(x, y, w, h));
}
}
private void drawRectangle() {
// .... etc
}
//.. .. etc
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D)g;
// set rendering hints for smooth ovals
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2d.setColor(SHAPE_COLOR);
// iterate through the shapeList ArrayList
for (Shape shape : shapeList) {
g2d.draw(shape); // and draw each Shape it holds
}
}
}