slider.java

java高级使用教程 全书一共分六章

// Slider - a slider widget
//
// This code is freely usable for any purpose.

package Acme.Widgets;

import java.awt.*;

/// A slider widget.
// <P>
// A slider is a widget that varies between a minimum and a maximum
// value. The user can drag a "thumb" to change the current value. As
// the slider is dragged, Motion() is called. When the slider is
// released, Release() is called. Override these two methods to give
// the slider behavior.
// <P>
// This is (strongly) based on a version by
// <A HREF="http://www.cs.brown.edu/people/amd/">Adam Doppelt</A>.
// <P>
// <A HREF="/resources/classes/Acme/Widgets/Slider.java">Fetch the software.</A><BR>
// <A HREF="/resources/classes/Acme.tar.gz">Fetch the entire Acme package.</A>

public class Slider extends Canvas
    {

    private static final int THUMB_SIZE = 14;
    private static final int BUFFER = 2;

    private static final int TEXT_HEIGHT = 15;
    private static final int TEXT_BUFFER = 3;

    private static final int DEFAULT_WIDTH = 100;
    private static final int DEFAULT_HEIGHT = 15;

    private static final int MIN_WIDTH = 2 * ( THUMB_SIZE + BUFFER + 1 );
    private static final int MIN_HEIGHT = 2 * ( BUFFER + 1 );

    private static final int DEFAULT_MIN = 1;
    private static final int DEFAULT_MAX = 100;

    int value, valueMin, valueMax;
    int pixel, pixelMin, pixelMax;
    Color barColor, thumbColor, lineColor, textColor;

    /// Constructor, all default values.
    public Slider()
	{
	setDefaults();
	}

    /// Constructor, some specified values.
    public Slider( int valueMin, int valueMax )
	{
	setDefaults();
	setMinimum( valueMin );
	setMaximum( valueMax );
	setValue( valueMin );
	}

    /// Constructor, some specified values.
    public Slider( int valueMin, int valueMax, int width )
	{
	setDefaults();
	setMinimum( valueMin );
	setMaximum( valueMax );
	setValue( valueMin );
	setWidth( width );
	}

    private void setDefaults()
	{
	valueMin = DEFAULT_MIN;
	valueMax = DEFAULT_MAX;
	thumbColor = getBackground();
	if ( thumbColor == null )
	    thumbColor = Color.lightGray;
	barColor = thumbColor.darker();
	textColor = getForeground();
	if ( textColor == null )
	    textColor = Color.black;
	lineColor = textColor;
	resize( DEFAULT_WIDTH, DEFAULT_HEIGHT + TEXT_HEIGHT );
	// setSize( DEFAULT_WIDTH, DEFAULT_HEIGHT + TEXT_HEIGHT );
	setValue( valueMin );
	}


    /// This method is called when the "thumb" of the slider is moved by
    // the user.  May be overridden to give the slider some behavior.
    public void motion()
	{
	}

    /// This method is called when the "thumb" of the slider is released
    // after being moved.  May be overridden to give the slider some behavior.
    public void release()
	{
	}


    /// Sets the maximum value for the slider.
    // @param num The new maximum.
    public void setMaximum( int num )
	{
	valueMax = num;
	if ( valueMin > valueMax )
	    valueMin = valueMax;
	setValue( value );
	}

    /// Sets the minimum value for the slider.
    // @param num The new minimum.
    public void setMinimum( int num )
	{
	valueMin = num;
	if ( valueMax < valueMin )
	    valueMax = valueMin;
	setValue( value );
	}

    /// Sets the current value for the slider. The thumb will move to
    // reflect the new setting.
    // @param num The new setting for the slider.
    public void setValue( int num )
	{
	value = num;

	if ( value < valueMin )
	    value = valueMin;
	else if ( value > valueMax )
	    value = valueMax;

	if ( value != valueMin )
	    pixel = (int) ( Math.round(
		Math.abs(
		    (double) ( value - valueMin ) /
		    (double) ( valueMax - valueMin ) ) *
		(double) ( pixelMax - pixelMin ) ) + pixelMin );
	else
	    pixel = pixelMin;

	repaint();
	}

    /// Sets the height of the slider. This is the height of the entire
    // slider canvas, including space reserved for displaying the
    // current value.
    // @param num The new height.
    public void setHeight( int num )
	{
	if ( num < MIN_HEIGHT + TEXT_HEIGHT )
	    num = MIN_HEIGHT + TEXT_HEIGHT;
	resize( size().width, num );
	// setSize( getSize().width, num );
	repaint();
	}

    /// Sets the width of the slider. This is the width of the actual
    // slider box.
    // @param num The new width.
    public void setWidth( int num )
	{
	if ( num < MIN_WIDTH )
	    num = MIN_WIDTH;
	resize( num, size().height );
	// setSize( num, getSize().height );
	repaint();
	}

    /// Sets the color for the slider's bar. The "bar" is the rectangle
    // that the thumb slides around in.
    // @param color The new bar color.
    public void setBarColor( Color color )
	{
	barColor = color;
	repaint();
	}

    /// Sets the color for the slider's thumb. The "thumb" is the box that
    // the user can slide back and forth.
    // @param color The new thumb color.
    public void setThumbColor( Color color )
	{
	thumbColor = color;
	repaint();
	}

    /// Sets the line color for the slider - the little vertical line
    // on the thumb.
    // @param color The new line color.
    public void setLineColor( Color color )
	{
	lineColor = color;
	repaint();
	}

    /// Sets the color for the slider`s text.
    // @param color The new text color.
    public void setTextColor( Color color )
	{
	textColor = color;
	repaint();
	}


    /// Returns the current value for the slider.
    // @return The current value for the slider.
    public int getValue()
	{
	return value;
	}


    public void paint( Graphics g )
	{
	int width = size().width;
	// int width = getSize().width;
	int height = size().height;
	// int height = getSize().height;

	g.setColor( barColor );
	g.fill3DRect(
	    0, TEXT_HEIGHT, width, height - TEXT_HEIGHT, false );

	g.setColor( thumbColor );
	g.fill3DRect(
	    pixel - THUMB_SIZE, TEXT_HEIGHT + BUFFER,
	    THUMB_SIZE * 2 + 1, height - 2 * BUFFER - TEXT_HEIGHT, true );

	g.setColor( lineColor );
	g.drawLine(
	    pixel, TEXT_HEIGHT + BUFFER + 1, pixel, height - 2 * BUFFER );

	g.setColor( textColor );
	String str = String.valueOf( value );
	int strWidth = getFontMetrics( g.getFont() ).stringWidth( str );
	g.drawString( str, pixel - strWidth / 2, TEXT_HEIGHT - TEXT_BUFFER );
	}

    public void setBounds( int x, int y, int width, int height )
	{
	super.setBounds( x, y, width, height );
	pixelMin = THUMB_SIZE + BUFFER;
	pixelMax = width - THUMB_SIZE - BUFFER - 1;
	if ( value != valueMin )
	    pixel = (int) ( Math.round(
		Math.abs(
		    (double) ( value - valueMin ) /
		    (double) ( valueMax - valueMin ) ) *
		(double) ( pixelMax - pixelMin ) ) + pixelMin );
	else
	    pixel = pixelMin;
	}

    public boolean mouseDown( Event e, int x, int y )
	{
	if ( x >= pixel - THUMB_SIZE && x <= pixel + THUMB_SIZE )
	    {
	    if ( x < pixel )
		setValue( value - 1 );
	    else if ( x > pixel )
		setValue( value + 1 );
	    }
	else
	    mouseAction( x );
	motion();
	return true;
	}

    public boolean mouseDrag( Event e, int x, int y )
	{
	mouseAction( x );
	motion();
	return true;
	}

    public boolean mouseUp( Event e, int x, int y )
	{
	release();
	return true;
	}

    private void mouseAction( int x )
	{
	double percent;
	pixel = Math.min( Math.max( x, pixelMin ), pixelMax );

	if ( pixel != pixelMin )
	    percent = ( (double) pixel - pixelMin ) / ( pixelMax - pixelMin );
	else
	    percent = 0;

	value =
	    (int) ( Math.round( percent * (double) ( valueMax - valueMin ) ) ) +
	    valueMin;

	repaint();
	}

    }