frameddisplay.java

书籍"Java_面向事件编程"的附带光盘代码

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

// A FramedDisplay is a composite graphic intended to serve
// as a frame in which a program can display information.
public class FramedDisplay {

    private static final int BORDER = 3;    // Border thickness
    private static final int ROUNDNESS = 5;   // Corner roundess
    
    // Colors used for the frame
    private static final Color BORDERCOLOR = Color.gray;
    private static final Color HIGHLIGHTCOLOR = Color.red;
    
    private FilledRoundedRect body;            // The background
    private FilledRoundedRect border;        // The border

    // Create the display area's background and border
    public FramedDisplay( double x, double y,
                          double width, double height,
                          DrawingCanvas canvas)  {
        border = new FilledRoundedRect( x, y, width, height,
                                        ROUNDNESS, ROUNDNESS, canvas);
        body = new FilledRoundedRect( x + BORDER, y + BORDER,
                                      width-2*BORDER, height-2*BORDER,
                                      ROUNDNESS, ROUNDNESS, canvas);
        border.setColor( BORDERCOLOR );
    }
    
    // This method should be overriden by any subclass so
    // it correctly positions the contents of the display
    protected void positionContents(  ) {   }

    // Change the border's color to make it stand out
    public void highlight() {  border.setColor( HIGHLIGHTCOLOR ); }

    // Restore the standard border color
    public void unHighlight() { border.setColor( BORDERCOLOR );  }
        
    // Return the x coord of the left edge of display area
    protected double displayLeft() {    return body.getX();   }
    
    // Return the y coord of the top edge of display area
    protected double displayTop() {    return body.getY();    }
    
    // Return the width of the display area
    protected double displayWidth() { return body.getWidth();  }
    
    // Return the height of the display area
    protected double displayHeight() { return body.getHeight();  }

    // move the parts of the framed display by offsets
    public void move(double xoff, double yoff) {
        border.move(xoff, yoff);
        body.move(xoff, yoff);
        positionContents();
    }
    
    // move the parts of the frame to a specific location
    public void moveTo( double x, double y ) {
        move( x - border.getX(), y - border.getY() );
    }
}