dial.java

learning java的源代码。书中每个实例都有相关的代码example。

//file: Dial.java
import java.awt.*;
import java.awt.event.*;
import java.beans.*;
import java.util.*;
import javax.swing.*;

public class Dial extends JComponent {
  int minValue, value, maxValue, radius;

  public Dial(  ) { this(0, 100, 0); }

  public Dial(int minValue, int maxValue, int value) {
    this.minValue = minValue;
    this.maxValue = maxValue;
    this.value = value;
    setForeground(Color.lightGray);

    addMouseListener(new MouseAdapter(  ) {
      public void mousePressed(MouseEvent e) { spin(e); }
    });
    addMouseMotionListener(new MouseMotionAdapter(  ) {
      public void mouseDragged(MouseEvent e) { spin(e); }
    });
  }

  protected void spin(MouseEvent e) {
    int y = e.getY(  );
    int x = e.getX(  );
    double th = Math.atan((1.0 * y - radius) / (x - radius));
    int value=((int)(th / (2 * Math.PI) * (maxValue - minValue)));
    if (x < radius)
      setValue(value + maxValue / 2);
    else if (y < radius)
      setValue(value + maxValue);
    else
      setValue(value);
  }

  public void paintComponent(Graphics g) {
    Graphics2D g2 = (Graphics2D)g;
    int tick = 10;
    radius = getSize(  ).width / 2 - tick;
    g2.setPaint(getForeground().darker(  ));
    g2.drawLine(radius * 2 + tick / 2, radius,
        radius * 2 + tick, radius);
    g2.setStroke(new BasicStroke(2));
    draw3DCircle(g2, 0, 0, radius, true);
    int knobRadius = radius / 7;
    double th = value * (2 * Math.PI) / (maxValue - minValue);
    int x = (int)(Math.cos(th) * (radius - knobRadius * 3)),
    y = (int)(Math.sin(th) * (radius - knobRadius * 3));
    g2.setStroke(new BasicStroke(1));
    draw3DCircle(g2, x + radius - knobRadius,
                 y + radius - knobRadius, knobRadius, false );
  }

  private void draw3DCircle( Graphics g, int x, int y,
                             int radius, boolean raised) {
    Color foreground = getForeground(  );
    Color light = foreground.brighter(  );
    Color dark = foreground.darker(  );
    g.setColor(foreground);
    g.fillOval(x, y, radius * 2, radius * 2);
    g.setColor(raised ? light : dark);
    g.drawArc(x, y, radius * 2, radius * 2, 45, 180);
    g.setColor(raised ? dark : light);
    g.drawArc(x, y, radius * 2, radius * 2, 225, 180);
  }

  public Dimension getPreferredSize(  ) {
    return new Dimension(100, 100);
  }

  public void setValue(int value) {
    firePropertyChange( "value", this.value, value );
    this.value = value;
    repaint(  );
    fireEvent(  );
  }
  public int getValue(  )  { return value; }
  public void setMinimum(int minValue)  { this.minValue = minValue; }
  public int getMinimum(  )  { return minValue; }
  public void setMaximum(int maxValue)  { this.maxValue = maxValue; }
  public int getMaximum(  )  { return maxValue; }

  public void addDialListener(DialListener listener) {
    listenerList.add( DialListener.class, listener );
  }
  public void removeDialListener(DialListener listener) {
    listenerList.remove( DialListener.class, listener );
  }

  void fireEvent(  ) {
    Object[] listeners = listenerList.getListenerList(  );
    for ( int i = 0; i < listeners.length; i += 2 )
      if ( listeners[i] == DialListener.class )
        ((DialListener)listeners[i + 1]).dialAdjusted(
          new DialEvent(this, value) );
  }

  public static void main(String[] args) {
    JFrame f = new JFrame("Dial v1.0");
    f.addWindowListener( new WindowAdapter(  ) {
      public void windowClosing(WindowEvent e) { System.exit(0); }
    });
    f.setSize(150, 150);

    final JLabel statusLabel = new JLabel("Welcome to Dial v1.0");
    final Dial dial = new Dial(  );
    JPanel dialPanel = new JPanel(  );
    dialPanel.add(dial);
    f.getContentPane(  ).add(dialPanel, BorderLayout.CENTER);
    f.getContentPane(  ).add(statusLabel, BorderLayout.SOUTH);

    dial.addDialListener(new DialListener(  ) {
      public void dialAdjusted(DialEvent e) {
        statusLabel.setText("Value is " + e.getValue(  ));
      }
    });
    f.setVisible( true );
  }
}