framedbarmeter.java

书籍"Java_面向事件编程"的附带光盘代码

import objectdraw.*;
import java.awt.*;

public class FramedBarMeter extends FramedDisplay
{   
      // Space between the frame and the bar
    private static final double INSET=2;
    
      // The bar itself
    private FilledRect bar;

      // Fraction currently being displayed
    private double fraction;
    
      // Create frame and bar filling a fraction of the display
    public FramedBarMeter( double aFraction,
                           double x, double y,
                           double width, double height,
                           DrawingCanvas canvas) {
   
        super( x, y, width, height, canvas );
     
        fraction = aFraction;
        
        bar = new FilledRect( displayLeft()+INSET, 
                              displayTop()+INSET, 
                              (displayWidth()-2*INSET)*fraction, 
                              displayHeight()-2*INSET, canvas);
        bar.setColor(Color.blue);
    }
    
      //  Change the fraction of the display filled by the bar
    public void setFraction( double aFraction) {
        fraction = aFraction;
        positionContents();
    }

      //  Resize and reposition the bar appropriately 
    protected void positionContents(  ) {
    
        bar.moveTo( displayLeft()+INSET, displayTop()+INSET );
        bar.setWidth( (displayWidth()-2*INSET)*fraction );
        bar.setHeight( displayHeight()-2*INSET );
    }

}