Skip to main content

Learning Dojo: Scripting Widgets

What Exactly is a Widget?
Dijit components are handy encapsulations or user interface functionality. That's what made Visual Basic's component based technology so appealing twenty years ago.

Widgets are components in the abstract sense, but what are they from a coding standpoint?
So far, we have a vague idea, at least for the declarative case, that a widget is a snippet of HTML with a dojoType, like this:

<div dojoType="dijit.layout.ContentPane" href="http://localhost/too/many/slashes.html" ></div>

There are four main ways to get a widget refrence:

  • You can set the jsId= attribute in the tag, which creates a global JavaScript variable with that name
  • You can use dijit.byId(id). This is sueful if you had set the id= attribute on your widget
  • You can use dijit.byNode(nodeVariable) when you don't have the id attribute but you have the DOM node itself. You can usually get the node with dojo.query
  • Similarly, dijit.getEnclosingWidge(nodeVariable)  will get the "nearest" widget surrounding it, if you have a DOM node inside the widget.
  • You can read an attribute or call a method on another object that returns a widget. For example, the attribute adjacent of dojo.layout.StackContainer gives you back a widget

For examples:
dojobook.widgets.DeclarativePortal.setUrl = function() {
// returns back the div tag of the selected AccordionPane
var paneList = dijit.byId("ups" );

// Get the selected dijit.layout.AccordionPane. This is
// kept in selectedChildWidget
var chosenPane = paneList.selectedChildWidget;
// Now, get the value from the textbox. Note we can use
// dojo.byId() here because the .value property is a property of Node
var newUrl = dojo.byId("newUrl" ).value;
// Change the URL from which the content comes. Using setHref
// changes the content right away.
chosenPane.setHref("services/pure_proxy.php?url=" + newUrl);
}

...

<label for="newUrl">New URL:</label>
<input type="text" length="50" id="newUrl">
<button dojoType="dijit.form.Button" />
Set 
<script type="dojo/method" event="onClick" args="evt"> dojobook.widgets.DeclarativePortal.setUrl();
</script>
</button>
</body></html>



Comments

Popular posts from this blog

Quicksort implementation by using Java

 source: http://www.algolist.net/Algorithms/Sorting/Quicksort. The divide-and-conquer strategy is used in quicksort. Below the recursion step is described: 1st: Choose a pivot value. We take the value of the middle element as pivot value, but it can be any value(e.g. some people would like to pick the first element and do the exchange in the end) 2nd: Partition. Rearrange elements in such a way, that all elements which are lesser than the pivot go to the left part of the array and all elements greater than the pivot, go to the right part of the array. Values equal to the pivot can stay in any part of the array. Apply quicksort algorithm recursively to the left and the right parts - the previous pivot element excluded! Partition algorithm in detail: There are two indices i and j and at the very beginning of the partition algorithm i points to the first element in the array and j points to the last one. Then algorithm moves i forward, until an element with value greater or equal

Live - solving the jasper report out of memory and high cpu usage problems

I still can not find the solution. So I summary all the things and tell my boss about it. If any one knows the solution, please let me know. Symptom: 1.        The JVM became Out of memory when creating big consumption report 2.        Those JRTemplateElement-instances is still there occupied even if I logged out the system Reason:         1. There is a large number of JRTemplateElement-instances cached in the memory 2.     The clearobjects() method in ReportThread class has not been triggered when logging out Action I tried:      About the Virtualizer: 1.     Replacing the JRSwapFileVirtualizer with JRFileVirtualizer 2.     Not use any FileVirtualizer for cache the report in the hard disk Result: The japserreport still creating the a large number of JRTemplateElement-instances in the memory        About the work around below,      I tried: item 3(in below work around list) – result: it helps to reduce  the size of the JRTemplateElement Object        

Stretch a row if data overflows in jasper reports

It is very common that some columns of the report need to stretch to show all the content in that column. But  if you just specify the property " stretch with overflow' to that column(we called text field in jasper report world) , it will just stretch that column and won't change other columns, so the row could be ridiculous. Haven't find the solution from internet yet. So I just review the properties in iReport one by one and find two useful properties(the bold  highlighted in example below) which resolve the problems.   example: <band height="20" splitType="Stretch" > <textField isStretchWithOverflow="true" pattern="" isBlankWhenNull="true"> <reportElement stretchType="RelativeToTallestObject" mode="Opaque" x="192" y="0" width="183" height="20"/> <box leftPadding="2"> <pen lineWidth="0.25"/>