<!-- 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(' <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: 2024/11/27 06:20,
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