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Oracle Tips by Burleson |
Lists of
Values (LOV)
A LOV is a reusable list that can be built
dynamically with a SQL select statement or with a static set of values
typed in by the developer. Examples of static LOVs are:
The values in dynamic LOV’s are populated using a
SQL select statement such as:
select
description d, manufacturer_id r
from manufacturer
order by 1;
LOV’s can be used in forms, in tabular form
columns, in reports using Display as Text based on LOV, and select
lists. More explanation on creating and using LOV’s is included later
in this book.
Shortcuts
Shortcuts
enable the creation of reusable HTML or PL/SQL code. For an idea of
how this is used, the select list in the Conditional Display region
for a button is shown in Figure 6.10. There is a button displayed
after the select list followed by a list of items shown directly below
the select list. In the HTML DB development environment, this was
done using a shortcut. The name of the shortcut is then placed in the
Post Element Text of the select list item. This example shows that
HTML DB is actually written in HTML DB.
As an exercise to demonstrate how to create and
use the developer’s own shortcut, a page item that displays a date
page item will be created. A link will be provided on the side of the
page item that will allow the user to click on it and set the item to
today’s date.
This is defined in the following four step
process:
1.
Create a blank application page named Shortcuts. In the Page
Attributes, add the following text to the HTML Header section. This
is using the functions.js script provided as part of HTML DB. It
provides the source code for the setValue() function used later in the
shortcut. What is being accomplished here is borrowing some code
provided with the installation of HTML DB.
<script src="#IMAGE_PREFIX#javascript/functions.js"
type="text/javascript"></script>
2.
Create a shortcut from scratch by going to Shared Components
àShortcuts.
-
On the Creation Method page, select From Scratch and
click Next.
-
On the Shortcut Attributes page:
-
Name: SET_TODAYS_DATE.
-
Type: PL/SQL Function Body.
-
Shortcut: Enter the text from below. The file is in the Code
Depot.
-
Click Create.
Not only is the setValue JavaScript
function provided by HTML DB going to be used in this example, the
above script references a gif image named r_blue_arrow.gif, which is
provided with HTML DB. Take note of the date format. It is possible
to change the date format to the developer’s preferred format.
Another thing that can be done is the use of a substitution string for
the date format to keep the date format consistent throughout the
application. One such substitution string would be
PICK_DATE_FORMAT_MASK. If so, the statement would look something like
this:
d := to_char( sysdate, :PICK_DATE_FORMAT_MASK
);
When using the PICK_DATE_FORMAT_MASK as mentioned
above, the page item would be created as a Date Picker (with
application format mask).
3.
Create an HTML region on the page and then a Date Picker on the
page. This way the formats will always stay consistent whether the
Date Picker icon or the Shortcut icon is used.
4.
After the page item is created, edit the new page item and add
the text SET_TODAYS_DATE to Post Element Text
(include the double quotes), as
shown in Figure 6.11.
M
Be careful: Shortcuts are case-sensitive. It is
recommended that developers use the same case as the HTML DB
development team, which is UPPERCASE.
Apply Changes to the page item and run the
page. It should look similar to Figure 6.12. What has happened with
the SET_TODAYS_DATE shortcut is HTML DB has executed the PL/SQL block
and returned the following HTML code.
<a href="javascript:setValue('P2910_SHORTCUT_DATE','01/24/2006');">
<img src="/i/r_blue_arrow.gif" width="16" height="16"></a>
It is this HTML code that was rendered as
the Post Element Text for the page item. It creates an anchor tag and
an image tag displaying a blue arrow. Clicking on the blue arrow
executes the JavaScript in the anchor tag.
The example above used the PICK_DATE_FORMAT_MASK
substitution string. This is a best practice method of keeping all
dates consistent throughout an application.
This is not the extent of the usefulness of
shortcuts. The sample in Figure 6.10 is created with a shortcut that
is an elaborate PL/SQL program returning a string of HTML source code.
Files
The files in this shared component are stored in
the HTML DB repository. From the repository, they can be referenced
in HTML code as described below.
Cascading Style Sheets and Static Files from the
information on JavaScript are covered in a later chapter of this book.
Images
Images can be
stored in the HTML DB repository and rendered in an application page.
The process and explanation of adding an image to the repository
follows:
1.
Navigate to the Shared Components page.
2.
Click on the Images link.
3.
Click on the Create button.
4.
On the Create Image page:
There are two ways to add the image to the
repository. It can either be associated with an application or with
the workspace. Adding it to the workspace is done by selecting the No
Application Associated option. If the image is added to the
workspace, it can be referenced by all applications in the workspace.
If it is added to a particular application, it can only be referenced
by that application.
5.
Upon completion, the program will return to the Images page
showing a list of images in the repository.
Referencing Images
When images are
referenced from the repository, it is done by using substitution
strings. The two options are:
-
#WORKSPACE_IMAGES#: Use this substitution string if the
image is either associated with an application other
than the developer’s own or associated with the workspace using
the No Application Associated option.
-
#APP_IMAGES#: Use this substitution string if the image
is loaded into the repository and associated with the current
application.
Examples
The image can be rendered into a region of type
PL/SQL by adding the following code for the region source:
htp.img( '#WORKSPACE_IMAGES#EasyHTMLDB.gif'
);
htp.img( '#APP_IMAGES#EasyHTMLDB.gif'
);
To use a loaded image as the logo for the
application, it can be set in the Application Attributes page as shown
in Figure 6.13.
There is additional information about working with
images in a later section of this book.
The above book excerpt is from:
Easy HTML-DB
Oracle Application Express
Create Dynamic
Web Pages with OAE
ISBN 0-9761573-1-4
Michael Cunningham & Kent
Crotty
http://www.rampant-books.com/book_2005_2_html_db.htm
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