如何在JFrame上画一条曲线？

cuij7718：
具体该如何完成？
能否贴出代码？

import java.awt.*;
import java.awt.geom.*;
import java.util.*;
import java.awt.event.*;
import javax.swing.*;public class Sketch
{
   public static void main(String[] args)
   {
      SketchFrame frame = new SketchFrame();
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.show();
   }
}/**
   A frame with a panel for sketching a figure
*/
class SketchFrame extends JFrame
{
   public SketchFrame()
   {
      setTitle("Sketch");
      setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);      // add panel to frame      SketchPanel panel = new SketchPanel();
      Container contentPane = getContentPane();
      contentPane.add(panel);
   }   public static final int DEFAULT_WIDTH = 300;
   public static final int DEFAULT_HEIGHT = 200;
}/**
   A panel for sketching with the keyboard.
*/
class SketchPanel extends JPanel
{
   public SketchPanel()
   {
      last = new Point2D.Double(100, 100);
      lines = new ArrayList();
      KeyHandler listener = new KeyHandler();
      addKeyListener(listener);
      setFocusable(true);
   }   /**
      Add a new line segment to the sketch.
      @param dx the movement in x direction
      @param dy the movement in y direction
   */
   public void add(int dx, int dy)
   {
      // compute new end point
      Point2D end = new Point2D.Double(last.getX() + dx,
         last.getY() + dy);      // add line segment
      Line2D line = new Line2D.Double(last, end);
      lines.add(line);
      repaint();      // remember new end point
      last = end;
   }   public void paintComponent(Graphics g)
   {
      super.paintComponent(g);
      Graphics2D g2 = (Graphics2D)g;      // draw all lines
      for (int i = 0; i < lines.size(); i++)
         g2.draw((Line2D)lines.get(i));
   }   private Point2D last;
   private ArrayList lines;   private static final int SMALL_INCREMENT = 1;
   private static final int LARGE_INCREMENT = 5;   private class KeyHandler implements KeyListener
   {
      public void keyPressed(KeyEvent event)
      {
         int keyCode = event.getKeyCode();         // set distance
         int d;
         if (event.isShiftDown())
            d = LARGE_INCREMENT;
         else
            d = SMALL_INCREMENT;         // add line segment
         if (keyCode == KeyEvent.VK_LEFT) add(-d, 0);
         else if (keyCode == KeyEvent.VK_RIGHT) add(d, 0);
         else if (keyCode == KeyEvent.VK_UP) add(0, -d);
         else if (keyCode == KeyEvent.VK_DOWN) add(0, d);
      }      public void keyReleased(KeyEvent event) {}      public void keyTyped(KeyEvent event)
      {
         char keyChar = event.getKeyChar();         // set distance
         int d;
         if (Character.isUpperCase(keyChar))
         {
            d = LARGE_INCREMENT;
            keyChar = Character.toLowerCase(keyChar);
         }
         else
            d = SMALL_INCREMENT;         // add line segment
         if (keyChar == 'h') add(-d, 0);
         else if (keyChar == 'l') add(d, 0);
         else if (keyChar == 'k') add(0, -d);
         else if (keyChar == 'j') add(0, d);
      }
   }
}

可以直接在JFrame上画图，但是不好，可以在JFrame上加入一个JPanel，然后在JPanel上画图；
把你要画的图形的坐标值存放在数组中，然后调用paintComponent(Graphics g)方法，
在paintComponent()方法中，调用drawLine().
一段一段直到画完整个曲线。

caiyi0903：
你的代码画出的都是直角的折线，
能不能画出弧线出来？

JFrame本身具有核Applet类相同的方法Paint
public void paint(Graphics g)
{
}
通过就可绘出
java.awt.geom.*
中的line2D、GeneralPath也可。

如果是弧线得用GeneralPath类完成
用法基本上一样，只是多一个弧度问题（可以用默认的参数而不去考虑弧度）

利用类
QuadCurve2D (二次曲线)
和
CubicCurve2D （三次曲线）
可以绘制曲线，这两个类在包 java.awt.geom中
下面是我做的例子：import java.awt.*;
import java.awt.geom.*;
import javax.swing.*;public class CurveDemo extends JFrame
{
    //曲线参数
    Point2D.Double startQ=new Point2D.Double(50,75);
    Point2D.Double endQ=new Point2D.Double(150,75);
    Point2D.Double control=new Point2D.Double(80,25);    Point2D.Double startC=new Point2D.Double(50,150);
    Point2D.Double endC=new Point2D.Double(150,150);
    Point2D.Double controlStart=new Point2D.Double(80,100);
    Point2D.Double controlEnd=new Point2D.Double(160,100);

    QuadCurve2D.Double quadCurve;  //二次曲线
    CubicCurve2D.Double cubicCurve;//三次曲线
    public CurveDemo()
    {
      super("Curve Demo");
      setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

      quadCurve=new QuadCurve2D.Double(
   startQ.x,startQ.y,control.x,control.y,endQ.x,endQ.y);
      cubicCurve=new CubicCurve2D.Double(
   startC.x,startC.y,controlStart.x,controlStart.y,
   controlEnd.x,controlEnd.y,endC.x,endC.y);

      setSize(300,300);
      show();
     }

     public void paint(Graphics g)
     {
      Graphics2D g2D=(Graphics2D)g;
      g2D.setPaint(Color.BLUE);
      g2D.draw(quadCurve);
      g2D.draw(cubicCurve);
     }

     public static void main(String[] args)
     {
       CurveDemo curve=new CurveDemo();
      }
}

import java.awt.*;
import java.awt.geom.*;public class test
{
  public test(Point start, Point next)
  {
    curve=new GeneralPath();
    curve.moveTo(start.x, start.y);
    curve.lineTo(next.x, next.y);
  }  // 添加另一端
  public void modify(Point start, Point next) {
    curve.lineTo(next.x,
                 next.y);
  }  public java.awt.Rectangle getBounds() {
    return curve.getBounds();
  }  public void draw(Graphics2D g2D) {
    g2D.draw(curve); // 重绘弧线
  }  private GeneralPath curve;
}试一试

如果要显示刚才例子中曲线的控制点（控制弯曲度和方向），程序稍微复杂些，如下：//绘制曲线import java.awt.*;
import java.awt.geom.*;
import javax.swing.*;public class CurveDemo2 extends JFrame
{
         //曲线参数
         Point2D.Double startQ=new Point2D.Double(50,75);
Point2D.Double endQ=new Point2D.Double(150,75);
Point2D.Double control=new Point2D.Double(80,25);

Point2D.Double startC=new Point2D.Double(50,150);
Point2D.Double endC=new Point2D.Double(150,150);
Point2D.Double controlStart=new Point2D.Double(80,100);
Point2D.Double controlEnd=new Point2D.Double(160,100);

QuadCurve2D.Double quadCurve;  //二次曲线
CubicCurve2D.Double cubicCurve;//三次曲线     public CurveDemo2()
     {
      super("Curve Demo");
      setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

      quadCurve=new QuadCurve2D.Double(
   startQ.x,startQ.y,control.x,control.y,endQ.x,endQ.y);
      cubicCurve=new CubicCurve2D.Double(
   startC.x,startC.y,controlStart.x,controlStart.y,
   controlEnd.x,controlEnd.y,endC.x,endC.y);

      setSize(300,300);
      show();
     }

//添加内部类来显示曲线的控制点和切线
class Marker
{
  Ellipse2D.Double circle;
  Point2D.Double center;
  static final double radius=3;

  public Marker(Point2D.Double control)
  {
   center=control;
   circle=new Ellipse2D.Double(control.x-radius,control.y-radius,
       2.0*radius,2.0*radius);
  }

  public void draw(Graphics2D g2D)
  {
   g2D.draw(circle);
  }

  Point2D.Double getCenter()
  {
   return center;
  }
}

//设定控制点
Marker ctrlQuad=new Marker(control);
Marker ctrlCubic1=new Marker(controlStart);
Marker ctrlCubic2=new Marker(controlEnd);

public void paint(Graphics g)
{
  Graphics2D g2D=(Graphics2D)g;
  g2D.setPaint(Color.BLUE);
  g2D.draw(quadCurve);
  g2D.draw(cubicCurve);

  //下面显示控制点和切线
  g2D.setPaint(Color.RED);
  ctrlQuad.draw(g2D);
  ctrlCubic1.draw(g2D);
  ctrlCubic2.draw(g2D);

  Line2D.Double tangent=new Line2D.Double(startQ,ctrlQuad.getCenter());
  g2D.draw(tangent);
  tangent=new Line2D.Double(endQ,ctrlQuad.getCenter());
  g2D.draw(tangent);
  tangent=new Line2D.Double(startC,ctrlCubic1.getCenter());
  g2D.draw(tangent);
  tangent=new Line2D.Double(endC,ctrlCubic2.getCenter());
  g2D.draw(tangent);
}

     public static void main(String[] args)
     {
  CurveDemo2 curve=new CurveDemo2();
}
}

我已经搞定了。
本意是做出圆角的button来。
现在已经搞定了。
现把这个button的源码贴出来以饷各位帮助过我的兄弟们。

NJButton.java代码package UIControl.NJButton;import javax.swing.JButton;
import javax.swing.BorderFactory;
import java.awt.event.*;
import java.awt.*;
import java.awt.geom.*;
import UIControl.UIProperties.UIProperties;
import javax.swing.plaf.basic.BasicButtonUI;public class NJButton extends JButton
{
    private static final int m_ArcLen = 8;
    public NJButton()
    {
        try
        {
            jbInit();
            setContentAreaFilled(false);
        }
        catch (Exception ex)
        {
            ex.printStackTrace();
        }
    }    private void jbInit() throws Exception
    {
        this.setBorder(BorderFactory.createEtchedBorder());//设置Button的Border风格
        this.addMouseListener(new NJButton_this_mouseAdapter(this));//鼠标移入事件
        this.setBackground(UIProperties.cInnerButton); //设置Button的背景颜色
        this.setForeground(UIProperties.cForeButton); //设置Button的前景颜色
        this.setFont(UIProperties.fMiddle);//设置Button的字体大小
    }    protected void paintComponent(Graphics g)
    {
        boolean blRaise = true;
//        if (getModel().isArmed())
//        {
//            blRaise = false;
//        }
        g.setColor(this.getBackground());
        g.fill3DRect(0, 0, getSize().width - 1,
                   getSize().height - 1,blRaise);        //这个调用会画一个标签和焦点矩形。
        super.paintComponent(g);
    }
    //画按钮的边界
    protected void paintBorder(Graphics g)
    {
        g.setColor(new Color(128,128,255));
        drawRect(0, 0, getSize().width - 1,
                 getSize().height - 1, g);
    }    public void drawRect(int x, int y, int width, int height, Graphics g)
    {
        if ( (width < 0) || (height < 0))
        {
            return;
        }        if (height == 0 || width == 0)
        {
            g.drawLine(x, y, x + width, y + height);
        }
        else
        {
            g.drawArc(x ,y ,m_ArcLen,m_ArcLen,90,90);
            g.drawLine(x + (m_ArcLen/2), y, x + width - (m_ArcLen/2), y);
            g.drawArc(x + width - m_ArcLen,y ,m_ArcLen,m_ArcLen,0,90);
            g.drawLine(x + width, y + (m_ArcLen/2), x + width, y + height - (m_ArcLen/2));
            g.drawArc(x + width - m_ArcLen,y + height - m_ArcLen ,m_ArcLen,m_ArcLen,270,90);
            g.drawLine(x + width - (m_ArcLen/2), y + height, x + (m_ArcLen/2), y + height );
            g.drawArc(x ,y + height - m_ArcLen ,m_ArcLen,m_ArcLen,180,90);
            g.drawLine(x, y + height - (m_ArcLen/2), x, y + (m_ArcLen/2));
        }
    }    // 侦测点击事件
    Shape shape;
    public boolean contains(int x, int y)
    {// 如果按钮改变大小，产生一个新的形状对象。
        if (shape == null ||
            !shape.getBounds().equals(getBounds()))
        {
            shape = new Ellipse2D.Float(0, 0,
                                        getWidth(), getHeight());
        }
        return shape.contains(x, y);
    }
    /**
     * 鼠标移入事件方法
     * @param e    鼠标事件
     */
    void this_mouseEntered(MouseEvent e)
    {
        this.setCursor(new Cursor(Cursor.HAND_CURSOR)); //设置鼠标形状为手型
        this.setBackground(new Color(248, 249, 252));
    }    /**
     * 鼠标移出事件方法
     * @param e    鼠标事件
     */
    void this_mouseExited(MouseEvent e)
    {
        this.setBackground(UIProperties.cInnerButton);
    }
}class NJButton_this_mouseAdapter extends java.awt.event.MouseAdapter
{
    NJButton adaptee;    NJButton_this_mouseAdapter(NJButton adaptee)
    {
        this.adaptee = adaptee;
    }    public void mouseEntered(MouseEvent e)
    {
        adaptee.this_mouseEntered(e);
    }
    public void mouseExited(MouseEvent e)
    {
        adaptee.this_mouseExited(e);
    }
}UIProperties.java代码package UIControl.UIProperties;import java.awt.Color;
import java.awt.Font;public class UIProperties
{
    /**
     * 颜色属性
     */
    public static final Color cBackground = new Color(224,224,224);//一般背景颜色
    public static final Color cInnerFrame = new Color(237,237,237);//内置框颜色
    public static final Color cInnerFrame2 = new Color(237,245,245);//内置框颜色2
    public static final Color cInnerButton = new Color(237,241,248);//内置按钮颜色
    public static final Color cOuterButton = new Color(198,196,232);//外部按钮及滚动条颜色
    public static final Color cScrollFrame = new Color(125,125,255);//滚动条边框颜色
    public static final Color cForeNormal = new Color(10,49,107);//一般前景颜色
    public static final Color cForeButton = Color.BLACK;//按钮前景颜色    /**
     * 字体属性
     */
    public static final Font fSmall = new Font("Dialog", 0, 12);//小字体
    public static final Font fMiddle = new Font("Dialog", 0, 14);//中等字体
    public static final Font fLarge = new Font("Dialog", 0, 16);//大字体    public UIProperties()
    {
    }
}

上面兄弟们的方法我都没用，我用的是
g.drawArc(int x, int y, int width, int height,
int startAngle, int arcAngle);
方法搞定的。不过还是要感谢大家，散分了。：）

调试易

如何在JFrame上画一条曲线？

解决方案 »