Language Java Script Definitive Examples 16.3.TXT

 <!-- This example is from the book _JavaScript: The Definitive Guide_.     -->
<!-- Written by David Flanagan.  Copyright (c) 1996 O'Reilly & Associates. -->
<!-- This example is provided WITHOUT WARRANTY either expressed or implied.-->
<!-- You may study, use, modify, and distribute it for any purpose.        -->
<HEAD>
<SCRIPT LANGUAGE="JavaScript1.1">
// This is the constructor function for our new ToggleButton class.
// Calling it creates a ToggleButton object and outputs the required
// <A> and <IMG> tags into the specified document at the current location.  
// Therefore, don't call it for the current document from an event handler.
// Arguments:
//    document - the Document object the buttons will be created in.
//    checked - a boolean that says whether the button is initially checked.
//    label - an optional string that specifies text to appear after the button
//    onclick - an optional function to be called when the toggle button is
//              clicked.  It will be passed a boolean indicating the new
//              state of the button.  You can also pass a string, which will
//              be converted to a function which is passed a boolean argument
//              named "state"
function ToggleButton(document, checked, label, onclick)
{
    // first time called, document will be false.  Ignore this call.
    if (document ==index.html null) return;

    // The first time we are called (and only the first time) we have
    // to do some special stuff.  First, now that the prototype object
    // is created, we can set up our methods.  
    // Second, we've got to load the images that we'll be using.
    // Doing this will get the images in the cache for when we need them.
    if (!ToggleButton.prototype.over) {
        // Initialize the prototype object to create our methods
        ToggleButton.prototype.over = _ToggleButton_over;
        ToggleButton.prototype.out = _ToggleButton_out;
        ToggleButton.prototype.click = _ToggleButton_click;

        // Now create an array of image objects, and assign URLs to them.
        // The URLs of the images are configurable, and are stored in an
        // array property of this constructor function itself.  They will be
        // initialized below.  Because of a bug in Navigator, we've got
        // to maintain references to these images, so we store the array
        // in a property of the constructor rather than using a local variable.
        ToggleButton.images = new Array(4);
        for(var i = 0; i < 4; i++) {
            ToggleButton.images[i] =index.html new Image(ToggleButton.width,
                                               ToggleButton.height);
            ToggleButton.images[i].src = ToggleButton.imagenames[i];
        }
    }
    
    // Save some of the arguments we were passed.
    this.document = document;
    this.checked = checked;

    // Remember that the mouse is not currently on top of us.
    this.highlighted = false;

    // Save the onclick argument to be called when the button is clicked.
    // If it is not already a function, attempt to convert it
    // to a function that is passed a single argument, named state.
    this.onclick = onclick;
    if (typeof this.onclick == "string")
        this.onclick = new Function("state", this.onclick);

    // Figure out what entry in the document.images[] array the images
    // for this checkbox will be stored at.
    var index = document.images.length;

    // Now output the HTML code for this checkbox. Use <A> and <IMG> tags.
    // The event handlers we output here are confusing, but crucial to the
    // operation of this class.  The "_tb" property is defined below, as
    // are the over(), out(), and click() methods.
    document.write('&nbsp;<A HREF ="index.html" ' +
      'onMouseOver="document.images[' + index + ']._tb.over();return true;" '+
      'onMouseOut="document.images[' + index + ']._tb.out()" '+
      'onClick="document.images[' + index + ']._tb.click(); return false;">');
    document.write('<IMG SRC="' + ToggleButton.imagenames[this.checked+0] +'"'+
                   ' WIDTH=' + ToggleButton.width +
                   ' HEIGHT=' + ToggleButton.height +
                   ' BORDER=0 HSPACE=0 VSPACE=0 ALIGN="absmiddle">');
    if (label) document.write(label);
    document.write('</A>');

    // Now that we've output the <IMG> tag, save a reference to the
    // Image object that it created in the ToggleButton object.
    this.image =index.html document.images[index];

    // And also make a link in the other direction: from the Image object
    // to this ToggleButton object.  Do this by defining a "_tb" property
    // in the Image object.
    this.image._tb = this;
}

// This becomes the over() method.
function _ToggleButton_over()
{
    // Change the image, and remember that we're highlighted
    this.image.src = ToggleButton.imagenames[this.checked + 2];
    this.highlighted = true;
}

// This becomes the out() method
function _ToggleButton_out()
{
    // Change the image, and remember that we're not highlighted
    this.image.src = ToggleButton.imagenames[this.checked + 0];
    this.highlighted = false;
}

// This becomes the click() method
function _ToggleButton_click()
{
    // Toggle the state of the button, change the image, and call the
    // onclick method, if it was specified for this ToggleButton
    this.checked = !this.checked;
    this.image.src = ToggleButton.imagenames[this.checked+this.highlighted*2];
    if (this.onclick) this.onclick(this.checked);
}

// Initialize static class properties that describe the checkbox images.  These
// are just defaults.  Programs can override them by assigning new values.
// But the should only be overridden *before* any ToggleButtons are created.
ToggleButton.imagenames = new Array(4);            // create an array
ToggleButton.imagenames[0] = "images/togglebutton0.gif";  // the unchecked box
ToggleButton.imagenames[1] = "images/togglebutton1.gif";  // the box with a check mark
ToggleButton.imagenames[2] = "images/togglebutton2.gif";  // unchecked but highlighted
ToggleButton.imagenames[3] = "images/togglebutton3.gif";  // checked and highlighted
ToggleButton.width = ToggleButton.height = 25;     // size of all images
</SCRIPT>
</HEAD>

<BODY BGCOLOR="white">
<!-- Here's how we might use the ToggleButton class. -->
Optional extras:<BR>
<SCRIPT LANGUAGE="JavaScript1.1">
// Create the buttons
var tb1 =index.html new ToggleButton(document, true, "28.8K Modem<BR>");
var tb2 =index.html new ToggleButton(document, false, "Laser Printer<BR>");
var tb3 =index.html new ToggleButton(document, false, "Tape Backup Unit<BR>");
</SCRIPT>

<!-- Here's how we can use the ToggleButton objects from event handlers -->
<FORM>
<INPUT TYPE="button" VALUE="Report Button States"
       onClick="alert(tb1.checked + '\n' + tb2.checked + '\n' + tb3.checked)">
<INPUT TYPE="button" VALUE="Reset Buttons"
       onClick="if (tb1.checked) tb1.click();
                if (tb2.checked) tb2.click();
                if (tb3.checked) tb3.click();">
</FORM>
</BODY>

file: /Techref/language/JAVA/script/definitive/examples/16.3.txt, 7KB, , updated: 1997/4/4 10:59, local time: 2024/12/4 18:16,

^{3.138.61.52:LOG IN}

©2024 These pages are served without commercial sponsorship. (No popup ads, etc...).Bandwidth abuse increases hosting cost forcing sponsorship or shutdown. This server aggressively defends against automated copying for any reason including offline viewing, duplication, etc... Please respect this requirement and DO NOT RIP THIS SITE. Questions?

Please DO link to this page! Digg it! / MAKE!

<A HREF="http://sxlist.com/Techref/language/JAVA/script/definitive/examples/16.3.txt"> language JAVA script definitive examples 16</A>

Did you find what you needed?

Welcome to sxlist.com!

Site supported by
sales, advertizing,
& kind contributors
just like you!
Please don't rip/copy
(here's why
Copies of the site on CD
are available at minimal cost.