不久前我自己编写了一个星级小部件。随意使用它：
/**
* The StarRaring is a widget that displays a predefined number of images side
* by side to realize a "star ranking". This star ranking has listeners to
* listen to the user input and adjust the number of stars painted with full
* alpha. The remaining stars are painted with a user defined alpha value
* (default: 150)
*
* @author Sebastian Raubach
*
*/
public class StarRating extends Composite
{
private Image image;
private int hoverSelected = 0;
private int selected = 0;
private int nrOfImages = 5;
private int alpha = 150;
private int width;
private int height;
private boolean vertical = false;
/**
* <p>
* Creates a star rating widget with a default selection of 1 star
* </p>
*
* @param parent
* the hosting composite
* @param style
* the widget style
*/
public StarRating(Composite parent, int style)
{
super(parent, style);
/* Add dispose listener for the image */
addListener(SWT.Dispose, new Listener()
{
@Override
public void handleEvent(Event arg0)
{
if(image != null)
image.dispose();
}
});
/* Add custom paint listener that paints the stars */
addListener(SWT.Paint, new Listener()
{
@Override
public void handleEvent(Event e)
{
paintControl(e);
}
});
/*
* Keep track of the mouse movements and highlight possible new
* selection
*/
addListener(SWT.MouseMove, new Listener()
{
@Override
public void handleEvent(Event arg0)
{
int x = arg0.x;
int y = arg0.y;
/* Determine direction */
int step = (vertical ? height : width) + 1;
int location = vertical ? y : x;
/* Determine current index */
int current = (location / step);
/* Redraw if necessary */
if (current != hoverSelected)
{
hoverSelected = current;
redraw();
}
}
});
/* On mouse exit, reset selection */
addListener(SWT.MouseExit, new Listener()
{
@Override
public void handleEvent(Event arg0)
{
hoverSelected = selected;
redraw();
}
});
/* On mouse up, set new selection based on hover selection */
addListener(SWT.MouseUp, new Listener()
{
@Override
public void handleEvent(Event arg0)
{
selected = hoverSelected;
}
});
}
/**
* <p>
* Draws the images. Selected images are drawn with full alpha, unselected
* images with the user defined alpha value
* </p>
*
* @param event
* The source event
*/
private void paintControl(Event event)
{
GC gc = event.gc;
if (image != null)
{
int stepX = vertical ? 0 : width + 1;
int stepY = vertical ? height + 1 : 0;
for (int i = 0; i < nrOfImages; i++)
{
if (i == hoverSelected + 1)
gc.setAlpha(alpha);
gc.drawImage(image, 1 + stepX * i, 1 + stepY * i);
}
/* Reset alpha value */
gc.setAlpha(255);
}
}
/**
* <p>
* Returns the image used for the star painting
* </p>
*
* @return the image used for the star painting
*/
public Image getImage()
{
return image;
}
/**
* <p>
* Set the image used for the star painting
* </p>
*
* @param image
* the image used for the star painting
*/
public void setImage(Image image)
{
this.image = new Image(Display.getDefault(), image, SWT.IMAGE_COPY);
width = image.getBounds().width;
height = image.getBounds().height;
redraw();
}
/**
* <p>
* Set the number of stars to be shown on the star rating
* </p>
* <p>
* Minimum = 1, Maximum = unrestricted
* </p>
*
* @param nrOfStars
* the number of stars to be shown on the star rating
*/
public void setNrOfStars(int nrOfStars)
{
if (nrOfStars < 1)
throw new IllegalArgumentException("Invalid value for number of stars. Minimum: 1, Selection: " + nrOfStars);
else
nrOfImages = nrOfStars;
}
/**
* <p>
* Returns the number of stars to be shown on the star rating
* </p>
*
* @return the number of stars to be shown on the star rating
*/
public int getNrOfStars()
{
return nrOfImages;
}
/**
* <p>
* Get the number of selected stars of the star rating
* </p>
*
* @return the number of selected stars of the star rating
*/
public int getSelection()
{
return selected + 1;
}
/**
* <p>
* Set the number of selected stars of the star rating
* </p>
* <p>
* Minimum = 1, Maximum = nr. of stars available
* </p>
*
* @param selection
* the number of selected stars of the star rating
*/
public void setSelection(int selection)
{
if (selection < 0 || selection > nrOfImages)
throw new IllegalArgumentException("Invalid value for star selection. Minimum: 0, Maximum: " + nrOfImages + ", Selection: " + selection);
else
selected = selection - 1;
hoverSelected = selected;
}
/**
* <p>
* Set the alpha value used for painting the non-selected stars
* </p>
* <p>
* Minimum = 0, Maximum = 255
* </p>
*
* @param alpha
* The alpha value used for painting the non-selected stars
*/
public void setAlpha(int alpha)
{
if (alpha < 0 || alpha > 255)
throw new IllegalArgumentException("Invalid alpha value. Minimum: 0, Maximum: 255, Selection: " + alpha);
else
this.alpha = alpha;
}
/**
* <p>
* Returns the alpha value used for painting the non-selected stars
* </p>
*
* @return the alpha value used for painting the non-selected stars
*/
public int getAlpha()
{
return alpha;
}
/**
* <p>
* Set the orientation of the widget to vertical
* </p>
*
* @param vertical
* Set to true if the stars should be aligned in a vertical and
* to false if the stars should be aligned in a horizontal line
*/
public void setVertical(boolean vertical)
{
this.vertical = vertical;
}
/**
* <p>
* Returns the orientation of the widget
* </p>
*
* @return true, if the widget is vertical, false if the widget is
* horizontal
*/
public boolean getVertical()
{
return vertical;
}
@Override
public Point computeSize(int wHint, int hHint, boolean changed)
{
int overallWidth = 0;
int overallHeight = 0;
/* Determine the preferred dimensions of the widget */
if (image != null)
{
overallWidth = vertical ? width : width * nrOfImages + nrOfImages - 1;
overallHeight = vertical ? height * nrOfImages + nrOfImages - 1 : height;
}
/* Consider hints */
if (wHint != SWT.DEFAULT && wHint < overallWidth)
overallWidth = wHint;
if (hHint != SWT.DEFAULT && hHint < overallHeight)
overallHeight = hHint;
/* Return computed dimensions plus border */
return new Point(overallWidth + 2, overallHeight + 2);
}
public static void main(String[] args)
{
Display display = Display.getDefault();
Shell shell = new Shell(display);
shell.setLayout(new GridLayout(1, false));
StarRating star = new StarRating(shell, SWT.NONE);
star.setImage(new Image(display, "star.png"));
star.setVertical(true);
star.setNrOfStars(10);
star.setSelection(3);
star.setAlpha(100);
star.setVertical(false);
shell.pack();
shell.open();
while (!shell.isDisposed())
{
if (!display.readAndDispatch())
display.sleep();
}
display.dispose();
}
}
看起来像这样：