scrollpanedemo.java

java 完全探索的随书源码

// ScrollPaneDemo.java

import java.awt.*;

class ScrollPaneDemo extends Frame
{
   ScrollPaneDemo (String title)
   {
      super (title);

      // Create a MediaTracker object to track image loading.

      MediaTracker mt = new MediaTracker (this);

      // Applications require a Toolkit for image loading.

      Toolkit tk = Toolkit.getDefaultToolkit ();

      // Get the next image.

      Image im = tk.getImage ("iss.jpg");

      // Add image to MediaTracker object.

      mt.addImage (im, 0);

      // Force image to load.

      try
      {
           mt.waitForID (0);
      }
      catch (InterruptedException e) {}

      // Create a scroll pane container.

      ScrollPane sp = new ScrollPane ();

      // Create picture component.

      Picture pic = new Picture ();

      // Add picture to scroll pane.

      sp.add (pic);

      // Draw image.

      pic.draw (im);

      // Add scroll pane to frame (in center of its border layout).

      add (sp);

      // Set frame background (around scroll pane component/container)
      // to light gray.

      setBackground (Color.lightGray);

      // Set frame size to 400 by 400 pixels.

      setSize (400, 400);

      // Ensure that frame is visible.

      setVisible (true);
   }

   public static void main (String [] args)
   {
      new ScrollPaneDemo ("Scroll Pane Demo");
   }
}

class Picture extends Canvas
{
   private Image image;     // The current image.

   public void draw (Image image)
   {
      this.image = image;  // Save the current image.
      repaint ();          // Draw the image (update is called).
   }

   public Dimension getPreferredSize ()
   {
      // When the layout manager calls picture's getPreferredSize ()
      // method, this method will return a Dimension object that
      // tells the layout manager how much room to reserve for the
      // picture component.  Because the iss image is 640 x 481,
      // these dimensions are returned.

      return new Dimension (640, 481);
   }

   public void paint (Graphics g)
   {
      // Determine the upper-left image corner (x, y) coordinates so
      // that the image will be centered.

      int x = (getSize ().width - image.getWidth (this)) / 2;
      int y = (getSize ().height - image.getHeight (this)) / 2;

      // Draw the image.

      g.drawImage (image, x, y, this);
   }
}