在java中点击menuitems时如何改变形状和颜色

Question

Im无法改变某种形状的颜色。但是当用户点击一个菜单项时，它将成功转换成另一个形状。现在的问题是我想不出解决这个问题的解决方案。谁可以帮我这个事？非常感谢帮助。谢谢。

@Override 
    public void paintComponent(Graphics shapes) 
    { 
     super.paintComponent(shapes); 
     switch(colorNo) 
     { 
      case 0 : color = Color.RED;break; 
      case 1 : color = Color.BLUE;break; 
      case 2 : color = Color.MAGENTA;break; 
     } 
     switch(numbers) 
     { 
      case 0 : circle(shapes);break; 
      case 1 : rectangle(shapes);break; 
      case 2 : square(shapes);break; 
      case 3 : triangle(shapes);break; 
     } 
    } 

    public void circle(Graphics shapes) 
    { 
     shapes.setColor(color); 
     shapes.fillOval(250,100, 100, 100); 
    } 


    @Override 
    public void actionPerformed(ActionEvent click) { 
     if(click.getSource() == circle){ 
      numbers = 0; 
      repaint(); 
     }else if(click.getSource() == square){ 
      numbers = 1; repaint(); 
     }else if(click.getSource() == rectangle){ 
      numbers = 2; repaint(); 
     }else if(click.getSource() == triangle){ 
      numbers = 3; repaint(); 
     } 
     if(click.getSource() == red){ 
      colorNo = 0; repaint(); 
     } 

    } 

Answer 1

简单 - 在你的paintComponent方法，你超的的paintComponent电话后，和之前，你设定的形状您的switch语句，设置图形对象的颜色，在您设置的相同方式形状。您当然必须为每个颜色菜单项添加一个侦听器才能使其工作。

这是太如果您使用AbstractActions而不是让所有东西都共享相同的ActionListener，则会更容易和更清晰。例如，这段代码并不完全符合你所要做的，但它可以给你一些想法。

import java.awt.Color; 
import java.awt.Dimension; 
import java.awt.Graphics; 
import java.awt.event.ActionEvent; 

import javax.swing.*; 


public class MyShapes extends JPanel { 
    private static final int PREF_W = 400; 
    private static final int PREF_H = PREF_W; 
    private JMenuBar menuBar = new JMenuBar(); 
    private Color color = Color.WHITE; 

    public MyShapes() { 
     JMenu colorMenu = new JMenu("Color"); 
     colorMenu.add(new JMenuItem(new ColorAction("Black", Color.BLACK))); 
     colorMenu.add(new JMenuItem(new ColorAction("White", Color.WHITE))); 
     colorMenu.add(new JMenuItem(new ColorAction("Red", Color.RED))); 
     colorMenu.add(new JMenuItem(new ColorAction("Blue", Color.BLUE))); 
     colorMenu.add(new JMenuItem(new ColorAction("Green", Color.GREEN))); 
     menuBar.add(colorMenu); 
    } 

    @Override 
    protected void paintComponent(Graphics g) { 
     super.paintComponent(g); 
     g.setColor(color); 
     g.fillRect(0, 0, getWidth(), getHeight()); 
    } 

    @Override 
    public Dimension getPreferredSize() { 
     if (isPreferredSizeSet()) { 
      return super.getPreferredSize(); 
     } 
     return new Dimension(PREF_W, PREF_H); 
    } 

    public JMenuBar getMenuBar() { 
     return menuBar; 
    } 

    private class ColorAction extends AbstractAction { 
     private Color actionColor; 

     public ColorAction(String name, Color color) { 
      super(name); 
      this.actionColor = color; 
     } 

     @Override 
     public void actionPerformed(ActionEvent e) { 
      color = actionColor; 
      repaint(); 
     } 
    } 

    private static void createAndShowGui() { 
     MyShapes mainPanel = new MyShapes(); 

     JFrame frame = new JFrame("MyShapes"); 
     frame.setJMenuBar(mainPanel.getMenuBar()); 
     frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE); 
     frame.getContentPane().add(mainPanel); 
     frame.pack(); 
     frame.setLocationByPlatform(true); 
     frame.setVisible(true); 
    } 

    public static void main(String[] args) { 
     SwingUtilities.invokeLater(new Runnable() { 
      public void run() { 
       createAndShowGui(); 
      } 
     }); 
    } 
} 

需要注意的是，你可以画出你的形状以同样的方式 - 从菜单项的操作的actionPerformed方法内填充的变量。只有这次DrawShape接口类型的变量将用于其方法，这里是public void draw(Graphics g)。这种类型的程序设计模式被称为Command Pattern。例如：

import java.awt.Color; 
import java.awt.Dimension; 
import java.awt.Graphics; 
import java.awt.Graphics2D; 
import java.awt.Polygon; 
import java.awt.RenderingHints; 
import java.awt.event.ActionEvent; 

import javax.swing.*; 

@SuppressWarnings("serial") 
public class MyShapes extends JPanel { 
    private static final int PREF_W = 400; 
    private static final int PREF_H = PREF_W; 
    private JMenuBar menuBar = new JMenuBar(); 
    private Color color = null; 
    public DrawShape drawShape = null; 

    public MyShapes() { 
     // create and fill colorMenu 
     JMenu colorMenu = new JMenu("Color"); 
     colorMenu.add(new JMenuItem(new ColorAction("Black", Color.BLACK))); 
     colorMenu.add(new JMenuItem(new ColorAction("White", Color.WHITE))); 
     colorMenu.add(new JMenuItem(new ColorAction("Red", Color.RED))); 
     colorMenu.add(new JMenuItem(new ColorAction("Blue", Color.BLUE))); 
     colorMenu.add(new JMenuItem(new ColorAction("Green", Color.GREEN))); 

     // create and fill shapeMenu 
     JMenu shapeMenu = new JMenu("Shape"); 
     shapeMenu.add(new JMenuItem(new DrawShapeAction("Square", new DrawShape() { 

      @Override 
      public void draw(Graphics g) { 
       int x = getWidth()/4; 
       int y = getHeight()/4; 
       int width = getWidth()/2; 
       int height = getHeight()/2; 
       g.fillRect(x, y, width, height); 
      } 
     }))); 
     shapeMenu.add(new JMenuItem(new DrawShapeAction("Circle", new DrawShape() { 

      @Override 
      public void draw(Graphics g) { 
       int x = getWidth()/4; 
       int y = getHeight()/4; 
       int width = getWidth()/2; 
       int height = getHeight()/2; 
       g.fillOval(x, y, width, height); 
      } 
     }))); 
     shapeMenu.add(new JMenuItem(new DrawShapeAction("Triangle", new DrawShape() { 

      @Override 
      public void draw(Graphics g) { 
       int[] x = new int[3]; 
       int[] y = new int[3]; 
       x[0] = getWidth()/4; 
       x[1] = getWidth()/2; 
       x[2] = 3 * getWidth()/4; 
       y[0] = 3 * getHeight()/4; 
       y[1] = getHeight()/4; 
       y[2] = y[0]; 
       Polygon polygon = new Polygon(x, y, 3); 
       g.fillPolygon(polygon); 
      } 
     }))); 

     // add both JMenus to the JMenuBar 
     menuBar.add(colorMenu); 
     menuBar.add(shapeMenu); 
    } 

    @Override 
    protected void paintComponent(Graphics g) { 
     super.paintComponent(g); 

     // if either color or drawShape are not set, exit this method and draw nothing 
     if (color == null || drawShape == null) { 
      return; 
     } 

     // to smooth out the edges 
     Graphics2D g2 = (Graphics2D) g; 
     g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON); 

     // set color and call drawShape's draw method 
     g.setColor(color); 
     drawShape.draw(g); 
    } 

    @Override 
    public Dimension getPreferredSize() { 
     if (isPreferredSizeSet()) { 
      return super.getPreferredSize(); 
     } 
     return new Dimension(PREF_W, PREF_H); 
    } 

    public JMenuBar getMenuBar() { 
     return menuBar; 
    } 

    private class ColorAction extends AbstractAction { 
     private Color actionColor; 

     public ColorAction(String name, Color color) { 
      super(name); 
      this.actionColor = color; 
     } 

     @Override 
     public void actionPerformed(ActionEvent e) { 
      MyShapes.this.color = actionColor; 
      repaint(); 
     } 
    } 

    private class DrawShapeAction extends AbstractAction { 
     private DrawShape actionDrawShape; 

     public DrawShapeAction(String name, DrawShape drawShape) { 
      super(name); 
      this.actionDrawShape = drawShape; 
     } 

     @Override 
     public void actionPerformed(ActionEvent e) { 
      MyShapes.this.drawShape = actionDrawShape; 
      repaint(); 
     } 
    } 

    private interface DrawShape { 
     void draw(Graphics g); 
    } 

    private static void createAndShowGui() { 
     MyShapes mainPanel = new MyShapes(); 

     JFrame frame = new JFrame("MyShapes"); 
     frame.setJMenuBar(mainPanel.getMenuBar()); 
     frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE); 
     frame.getContentPane().add(mainPanel); 
     frame.pack(); 
     frame.setLocationByPlatform(true); 
     frame.setVisible(true); 
    } 

    public static void main(String[] args) { 
     SwingUtilities.invokeLater(new Runnable() { 
      public void run() { 
       createAndShowGui(); 
      } 
     }); 
    } 
}