hint_map.java

java编程的一些Applets例子。值得深入研究一下。

// hint_map.java
//
// Description
// ===========
//
// A Java class which implements image map like functionality, and
// displays a Win95 style help text for each area.
//
// Also provides the facility to load images (background, foreground), so that
// we have the appearance of transparency.
//
// Developed as a replacement for multiple copies of pbimg.java, which
// was becoming a piece of spahgetti, and had perfromnce problems if used
// multiple times within the same page to achieve a image map effect.
//
//
//
// Authors                Name                 email
// =======                ====                 ======
// 04-Feb-1996/SBH        Steve Hill           [e-mail]
//
// Revision History
// ================
// 04-Feb-1996/SBH      Created. Based on methods used in pbimg.java
//
// 13-Feb-1996/SBH      First released version, as unregistered shareware.
// (1.0)                Placed in CIS:JAVAUSER
//
// 21-Feb-1996/SBH      Added (optional) support for Netscape frames. Specifed by
// (1.2)                names as the last parameter for a hot area. 
//                      (NOTE: v1.1a was a 'special', and not generally
//                      released.
//
//                      Fixed bug whereby hint not displayed following call to
//                      paint() if not caused by mouse movement - moved
//                      repaint of hint to CopyOfftoOn()
//
//                      Incorporated workaround for problem in Netscape
//                      where HTML background loaded over a cached applet
//                      (just redraw 0.75 seconds after load)
//
// 27-Feb-1996/SBH      Fixed bug whereby after numerous reloads of the same
// (1.21)               applet, mouseDown messages were not delivered until
//                      the mouse moved within the hot_area (fix was to
//                      destry the timer thread when stop() called.
//-------------------------------------------------------------------------


import java.awt.*;
import java.util.StringTokenizer;
import java.net.URL;
import java.net.MalformedURLException;

class hot_area

// hot_area is a class which represents a polgon on screen, within the area
// of it's parent applet. The user interacts with hot areas as follows:
//
// o A Mouseclick will result in the URL being actioned, if valid
// o The mouse entering the area will result in a hint being displayed
//
//
//
{
private Polygon polyMyArea = new Polygon(); // The area covered
private hint_map Parent = null;             // My Parent applet    
private String  szHint;                     // The hint text to display
private String  szURLDescription;           // Description of my URL
private URL     uURL;                       // The URL to action
private boolean bHintVisible = false;       // When last called, was I visible?
private boolean bUseFrame = false;          // 21-Feb-96/SBH Load into Netscape Frame?
private String  szFrame;                    // 21-Feb-96/SBH The name of Netscape frame into which to load.   
public  boolean bInitialised = false;       // Everything ok.

  public hot_area ()
  {
  }

  public hot_area (String _szConfiguration, hint_map _Parent)

  // Description
  // ===========
  //
  // This takes a string of the format:
  //
  // "URL,Hint,X1,Y1,X2,Y2,.....Xn,Yn"
  //
  // and from it initialises the hot area.
  {
    int iX1 = 0;
    int iX2 = 0;
    int iX3 = 0;
    int iY1 = 0;
    int iY2 = 0;
    int iY3 = 0;

    String szTemp="";   //21-Feb-96/SBH Added to hold last param fetched

    boolean bRectangle = false; //(if only two points, we assume a rectangle)

    //debug ("New hot_area :" + _szConfiguration );

    //keep a track of our parent..

    Parent = _Parent;

    StringTokenizer st = new StringTokenizer(_szConfiguration, ",");

    try
    {
      szURLDescription   = st.nextToken();
      szHint             = st.nextToken();
    }
    catch (Exception e)
    {
      szHint = "Unable to determine URL" ;
    }

    try
    {
      uURL = new URL(Parent.getDocumentBase(),szURLDescription);
    }
    catch (MalformedURLException e)
    {
      uURL = null;
    }

    if (null != uURL)
      szURLDescription = uURL.toString();
    else
      szURLDescription = "Invalid URL";

    if (szURLDescription != null)
    {
      // We now try and work out our area.
      // There must be at least 4 numbers (x1,y1,x2,y2).
      try
      {
        iX1   = Integer.parseInt(st.nextToken());
        iY1   = Integer.parseInt(st.nextToken());
        iX2   = Integer.parseInt(st.nextToken());
        iY2   = Integer.parseInt(st.nextToken());
      }
      catch (Exception e)
      {
      szURLDescription = null;
      debug("Error: At least two points must be specified for hot_area '"+
            szHint + "'");
      }
      //debug(szHint +":" + iX1 + iY1 + iX2 + iY2);

      // Now, if there are no more points configured we have a rectangle
      // (we consider two points to be a rectangle)

      try
      {
        iX3   = Integer.parseInt(szTemp = st.nextToken());
        iY3   = Integer.parseInt(st.nextToken());
      }
      catch (Exception e)
      {
        bRectangle = true;
      }

      if (bRectangle)
      {
        polyMyArea.addPoint(iX1,iY1);
        polyMyArea.addPoint(iX2,iY1);
        polyMyArea.addPoint(iX2,iY2);
        polyMyArea.addPoint(iX1,iY2);
      //  debug (szHint +":Configured as rectangle");
        bInitialised = true;
      }
      else
      {
//        debug (szHint+ ": Polygon specified");
        polyMyArea.addPoint(iX1,iY1);
        polyMyArea.addPoint(iX2,iY2);
        polyMyArea.addPoint(iX3,iY3);

        while (!bInitialised)
        {
          try
          {
            iX1   = Integer.parseInt(szTemp=st.nextToken());
            iY1   = Integer.parseInt(st.nextToken());
            polyMyArea.addPoint(iX1,iY1);
          }
          catch (Exception e)
          {
            bInitialised = true;
          }
        }
      }
      if (!szTemp.equals(""))
      {
        szFrame   = szTemp;
        bUseFrame = true;
      }
    }
  }
//--------------------------------------------------------------------------
  public void MouseMove(int x, int y)
  // Description
  // ===========
  //
  // x and y are the absolute parameters of the cursor within the
  // applet. We check to see if they are inside us, and if so we should
  // display both a hint and a status.
  //
  //
  {
  if (polyMyArea.inside(x,y))
  {
    //Show our URL on the status line
    Parent.setStatusText(szURLDescription,true);
    Parent.setNewHintText(szHint);
    if (!bHintVisible)
    {
      //debug(szHint+": Mouse Entered");
      bHintVisible = true;
    }
    else
    {
    }
  }
  else
    {
      //Hide our URL, if on the status line
      Parent.setStatusText(szURLDescription,false);  
      if (bHintVisible)
      {
        //debug(szHint+": Mouse Left");
        bHintVisible = false;
      }
      else
      {
      }
    }
  }//MouseMove

//--------------------------------------------------------------------------
  public void MouseUp(int x, int y)
  // Description
  // ===========
  //
  // x and y are the absolute parameters of the cursor within the
  // applet. A mouse button has just been released. If it is in here
  // then do the jump
  //
  {
    // Check if inside, and hint visible. This means that the mouse went
    // down in this area as well.

    if (polyMyArea.inside(x,y) && bHintVisible)
    {
      if (bUseFrame) 
      {
        Parent.getAppletContext().showDocument(uURL,szFrame);
      }
      else
      {
        Parent.getAppletContext().showDocument(uURL);
      }
      Parent.showStatus("Fetching " + szURLDescription);
    }
  } //MouseUp

//--------------------------------------------------------------------------
  private void debug(String szText)
  {
   Parent.debug(szText);
  }

}
//========================================================================
public class hint_map extends java.applet.Applet implements Runnable {

    public String szVersion = "hint_map.class v1.21 (UNREGISTERED) (c) Steve Hill [e-mail]";

    Thread timer;
        
    Image imgStaticOffScreen = null; // Holds a copy of foreground over background 
    Image imgBackground      = null; // Used to load background
    Image imgForeground      = null; // Used to load foreground

    Graphics gcOff = null;   // Graphics context to draw on imgStaticOffScreen
    Graphics gcOn  = null;   // Graphics context to draw on visible screen.

    String szBackgroundFile; // URL of background as string
    String szForegroundFile; // URL of foreground as string

    int iOutstandingImageCount = 0; //Count of images not yet fully drawn offscreen.

    boolean bBackgroundOK = false; // Background file exists
    boolean bForegroundOK = false; // Foreground file exists
    Color   colBackground;         // Color of background (under backgroundimage)

    Dimension  dimOffScreen;       //size of offscreen image

    boolean bInitComplete = false;  // Interlock between paint() and run().

    hot_area HotAreas[] = new hot_area[20]; //array of all hot areas
    int      iMaxHotArea = 0;               // offset of last member of HotAreas    

    String   szLastStatus = "";             //Last vlaue shown on status bar    
    boolean  bStatusChanged = false;        //New status bar value    

    String  szHintText   = "";
    boolean bHintVisible = false;
    boolean bHintChanged = false;

    int lx,ly,lw,lh;                        // keep a copy of location of hint
                                            // in case we need to redraw during image fetch


    public void init()
    {
        System.out.println(szVersion);
        
        //Load up the background color from a hex triplet

        //debug("Entered init()");

        colBackground = getColorFromParam("bgcolor",Color.gray);

        // we always use the same on-screen graphics context, get it now..
        gcOn = getGraphics();

        szBackgroundFile = getParameter("background");

        if (null != (imgBackground = getImage(getDocumentBase(),szBackgroundFile)))
        {
           bBackgroundOK = true;
           iOutstandingImageCount++;
        }

        szForegroundFile = getParameter("foreground");

        if (null != (imgForeground = getImage(getDocumentBase(),szForegroundFile)))
        {
           bForegroundOK = true;
           iOutstandingImageCount++;
        }

        maintainStaticImages();
        copyOfftoOn();

        // now initialise all the hot areas. 

        boolean bDone = false;
        int j = 1;

        while  (!bDone)
        {
         bDone = (null==(HotAreas[j] = HotAreaFromParam(j++)));
        }

        iMaxHotArea = --j;

        bInitComplete = true;

        //debug("Exited init()");
    } //init()


//----------------------------------------------------------------------------
// Added start() stop() back in when flicker re-appeared..as a test

    public void start() {
        timer = new Thread(this);
        timer.start();
    }
    public void stop() {
        timer.stop();

        // 27-Feb-1996/SBH Added following line to fix bug whereby mouseup
        // sometimes not seen until mousemove occurs.
        timer=null;
    }


//----------------------------------------------------------------------------
    public void setStatusText(String _szStatus, boolean bVisible)

    // Description
    // ===========
    // If bVisible is true, then we display this text. If bVisible is false, 
    // we set the status bar to empty, if the last string displayed was same
    // this one. This gives each hot_area apparent access to their own
    // status bar, with the last call with bVisible=true having priority.

    {
      if (bVisible)
      {
        showStatus(_szStatus);
        szLastStatus = _szStatus;
      }
      else
      {
        if (szLastStatus.equals(_szStatus))
        {
          szLastStatus = "";
          showStatus("");
        }
      }
        
    }//setStatusText()
//----------------------------------------------------------------------------
public void setNewHintText(String _szHint)

// Description
// ===========
// bVisible is true, then display szText as a hint.
// otherwise, hide the hint, if the current text shown is szText
// 
//

{
    // if someone wants to display a hint, we must

    bHintVisible |= true;

    // but check if it's different from the last one displayed (we
    // may not need to redraw otherwise)

    // if the new hint is null, make sure we set flag (as appropriate)
    // but don't call .equals()

    if (_szHint == null)
    {
      if (szHintText != null)
        bHintChanged = true;
        szHintText = null;
    }

    else
    {
      if (!_szHint.equals(szHintText))
      {
        bHintChanged = true;
        szHintText = _szHint;
      }
    }
}//setHintNewText()

//----------------------------------------------------------------------------
    private hot_area HotAreaFromParam(int iAreaNumber)
    
    // Description
    // ===========
    //
    // Create a hot_area, given an integer. If not created, return null
    //
    // It is assumed that the HTML contains a parameter hot_area<iAreaNumber>
    // 
    //

    {
      hot_area retArea = null;
      String szParamValue;

      szParamValue = getParameter("hot_area" + iAreaNumber);