Question

所以我想在我的盒子和三角形以及其他一些

上画画后清理我的窗户

形状。我需要点击一个按钮并撤消所有应该从

消失的所有内容窗口，一切都被清理干净了。

这里我做了一个方框，当我点击按钮框并在窗口中点击一个框显示

我点击。

我为三角形做了同样的事情。

这是主程序（只有框）：

    import java.awt.*;

    import java.awt.event.*;

    import javax.swing.*;

    public class Kaleidescope extends JFrame implements MouseListener, ActionListener,

            MouseMotionListener {

        Triangle L;

        Triangle[] triangles;

        int triangleCount;

        Box b;

        Box[] boxes; // 2-d array of Box objects, form a color pallet

        int boxCount; 

        JButton boxButton;

        Oval O;

        Oval[] ovals;

        int ovalCount;

        Oval v; // Oval x, y 

        int downX=0, downY=0, upX=0, upY=0;

        int x1, y1; // mousePressed

        int w1, z1; // mouseEntered

        int mode = 1; // 1 = line, 2= boxes, 3 = oval, 4= text, 5 = SG, twoLines = 7.

        JButton TriangleButton;

        JButton boxButton;

        boolean Boxe = false; // if true draw box

        JButton ovalButton;

        int x1, y1; // mousePressed

        int w1, z1; // mouseEntered

        public static void main(String[] args) 
        {

            System.out.println("hi there.");

            new Kaleidescope();

            setDefaultCloseOperation(EXIT_ON_CLOSE);

            addMouseListener(this);

            addMouseMotionListener(this);

             triangles = new Triangle[20];

             triangleCount = 0; 

             boxes = new Box[20];

             boxCount = 0; 

             ovals = new Oval[20];
             ovalCount = 0;

            setLayout(new FlowLayout());

            boxButton = new JButton("Boxes");

            add(boxButton);

            boxButton.addActionListener(this);

            TriangleButton = new JButton("Triangles");

            add(TriangleButton);

            TriangleButton.addActionListener( this);

            ovalButton = new JButton("Oval");

            add(ovalButton);

            ovalButton.addActionListener( this);

            setSize(new Dimension(500, 500));

            setVisible(true);
        }

   // returns a random color

   public Color randomColor()

   {    

      int red = (int)(Math.random()*255);

      int green = (int)(Math.random()*255);

      int blue = (int)(Math.random()*255);

      return new Color(red,green,blue);    
   }

        public void mouseClicked(MouseEvent e) 
    {

        System.out.println("click at x="+e.getX()+" y="+e.getY()); 

        // convert window coords to box array indexes.

        // These were adjusted slightly after the video was made

        // (no more flakiness, these are right on target).

        int boxi = (e.getX()-10)/20; // convert mouse x to box index

        int boxj = (e.getY()-40)/20;

        System.out.println("click at boxi="+boxi+" boxj="+boxj);  

        // set extra box to the color that we clicked on

            if (mode == 2) 
            {

                boxes[boxCount++] = new Box(e.getX(), e.getY(), randomColor());
            }    


              if ( mode == 1)

            {

               triangles[triangleCount++] = new Triangle(e.getX(), e.getY(), 

                   randomColor());

            }



            repaint();
        }

        public void actionPerformed(ActionEvent e) 

        {

         if      ( e.getSource()==TriangleButton ) { mode  = 1;}

     else if ( e.getSource()==boxButton ) { mode = 2;}

     else if ( e.getSource()==ovalButton) { mode = 3;}


    else if (e.getSource() == clearButton)

    {
        // release all existing boxes

        while (boxCount-- > 0) boxes[boxCount] = null;

            while (triangleCount-- > 0) triangles[triangleCount] = null;

            while (ovalCount-- > 0) ovals[ovalCount] = null;

    }

  repaint();   

        }

        public void mouseEntered(MouseEvent e) 

        {

        }

        public void mousePressed(MouseEvent e)

        {   

         x1 = e.getX();

     y1 = e.getY();

     downX = e.getX();

     downY = e.getY();

     if ( mode == 3)

      {
          v = new Oval(e.getX(),e.getY(), randomColor());

          ovals [ovalCount]= v;

          ovalCount++; 

      }

   repaint();

        }

        public void mouseExited(MouseEvent e) 
        {

        }

        public void mouseReleased(MouseEvent e) 
        {

        }
public void mouseMoved( MouseEvent e ) {}

public void mouseDragged（MouseEvent e）

{

  upX = e.getX();

  upY = e.getY();

  if ( mode ==3)

  {

      int width;

      int height;

      width = upX - downX;

      height = upY - downY;

      v.w = width; 

      v.h = height; 

  }

  repaint();

}

        public void paint(Graphics g) 
        {
            super.paint(g);   

            for (int i = 0; i < boxCount; i++) 

            {
                boxes[i].drawMe(g);

            }

  for ( int a=0; a<triangleCount; a++)

   {

      triangles[a].drawMe(g);

   }   

  for ( int b=0; b<ovalCount; b++)

  {

      ovals[b].drawMe(g);

  }

 }

}

这是盒子的另一个类（连接到主程序来绘制我的盒子）

import java.awt.*;

public class Box 
{
    protected Color color;

    protected int x, y; // pixels from upper left to upper left corner

    // make a box

    public Box(int x1, int y1, Color c1) 
    {
        x = x1;

        y = y1;

        color = c1;
    }

    public void drawMe(Graphics g) 

    {
        g.setColor(color);

        g.fillRect(x, y, 20, 20);
    }

    public void setColor(Color c) 

    {
        color = c;
    }

    public Color getColor() 

    {
        return color;
    }
}

Here is another class

package kaleidescope;

public class Point

{ 

int x;

int y;

public Point( int x1, int y1 )

{

   x = x1; y = y1;
}

}

此类

package kaleidescope;

import java.awt.*;

public abstract class Shape

{

protected Color color;

abstract public void drawMe( Graphics g ); 

}

Answer 1

只需添加“清除”按钮，然后在处理程序中将boxCount设置为零并调用repaint()。您必须调整actionPerformed以检测清除按钮何时为源。

编辑：这是你的代码修改后添加一个清晰的功能（仅适用于盒子，但见下文）：

JButton boxButton;
JButton clearButton; // NEW

public static void main(String[] args) 
{
    System.out.println("hi there.");
    new Kaleidescope();
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    addMouseListener(this);
    addMouseMotionListener(this);
    boxes = new Box[20];
    boxCount = 0;
    setLayout(new FlowLayout());
    boxButton = new JButton("Boxes");
    add(boxButton);
    boxButton.addActionListener(this);

    // NEXT 3 LINES ARE NEW
    clearButton = new JButton("Clear");
    add(clearButton);
    clearButton.addActionListener(this);

    setSize(new Dimension(500, 500));
    setVisible(true);
}

public void actionPerformed(ActionEvent e) 
{
    if (e.getSource() == boxButton) 
    {
        mode = 2;
        repaint();
    }
    else if (e.getSource() == clearButton)
    {
        // release all existing boxes
        while (boxCount-- > 0) boxes[boxCount] = null;

        // TODO: zero out all other display list items as well

        // redraw everything (which is now nothing)
        repaint();
    }
}

由于您没有显示如何维护其他形状的列表，因此我无法为TODO部分提供特定代码。但是，它看起来与我发布的内容非常相似。

编辑2：

以下是我建议如何切换使用ArrayList而不是数组的方法。我将描述如何改变盒子的东西;其他形状也类似。

导入java.util.ArrayList。
消除变量boxCount。
更改
```
Box[] boxes;
```
到
```
ArrayList<Box> boxes;
```

替换

行

boxes = new Box[20];
boxCount = 0;

使用：

boxes = new ArrayList<Box>(); // or new ArrayList<>() for Java 7+ compiler

替换行：

boxes[boxCount++] = new Box(e.getX(), e.getY(), randomColor());

使用：

boxes.add(new Box(e.getX(), e.getY(), randomColor()));

替换行：

while (boxCount-- > 0) boxes[boxCount] = null;

使用：

boxes.clear();

替换绘图循环：

for (int i = 0; i < boxCount; i++) 
{
    boxes[i].drawMe(g);
}

使用：

for (Box box : boxes) {
    box.drawMe(g);
}

就是这样。从您到目前为止发布的代码中，我没有看到为盒子，三角形和椭圆形成单独列表的原因。我建议您只有一个Shape个对象的显示列表，其中包含要绘制的所有形状（盒子，三角形和椭圆形都混合在一起）。但是，在代码的其他部分中，您可能会分别处理每个对象列表;这可能会改变我的建议。

如何撤消我绘制的所有内容

1 个答案: