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Oracle Tips by Burleson |
Radio
Buttons
Radio buttons are used to give the user a list of
choices where they can only pick one value from the list. Unlike a
Select List, all the choices for the radio button are given on the
page when rendered. Because of this, it is a best practice to limit
the number of choices to only a few. An example of a Radio Button
group is shown in Figure 10.29.
The user will only be allowed to select one of the
colors which will then specify the value for the page item.
Radio button page items are based on a LOV. In
the LOV, the display values are specified and the value the page item
will be set to when the radio button is selected. The Color example
above will be created in the following exercise.
To create a Select List in a region, click on the  icon
in the Items region on the Page Definition page:
1. On
the Item Type page, select the type of list to create. This case will
just use the standard type Radiogroup and click Next. Table 10.4
shows the different types of Radiogroups available.
|
RADIOGROUP |
DESCRIPTION |
|
Radiogroup |
This is the standard type of radio group
and just displays the text and provides a return value. |
|
Radiogroup with Redirect |
This type of radio group will not submit
the page for processing, but it will redirect the page back to
itself. This can be used to set the session state for the item,
but not submit. It is commonly used when something else on the
page may depend on the value for the radio group in a condition.
|
|
Radiogroup (with Submit) |
This type of radio group will submit the
page when an item in the radio group is selected. |
Table 10.4:
The types of Radiogroups
2.
On the Display Position and Name page.
-
Item
Name: Enter the name of the item.
-
Sequence: Enter the sequence based on
where the page item is to be displayed in the region.
-
Region: Select the region in which this
page item should be displayed.
-
Click Next.
3.
This is the important page. This is where the display values
are defined and the result which will be set to the page item. There
are some options to fill in which are explained below. For this
example, the Display Null has been set to NO. A simple static LOV
will be used for this example. The List of Values definition is:
STATIC:Red;R,White;W,Blue;B,Green;G,Purple;P,Yellow;Y
If the values were
saved in a table, a Select statement could be used to also populate
the LOV. The Select statement might look like:
select color_name display_value,
color_code result
from color_table
order by color_name;
Answering YES here will cause the
select list to be rendered with an extra item indicating null.
The default text that will be displayed in the select list to
indicate null is %.
-
: Enter the text to be displayed in the event the
session state for the select list is null. In Figure 10.24, the
text Select a Department will be displayed in the select list when
a value has not been selected from the list.
-
: Enter a value to be used in session state if no item
is selected in the select list. This item can be used in page
validations to check if an item has been selected. It is common
to use a -1 for numeric data and an X for character data.
-
Click Next.
4.
On the Item Attributes page:
-
:
Enter the text to display next to the select list. Enter Colors.
-
: Choose the position to place the label. Choose
Above.
-
: This is not used for radio buttons.
-
: Select the position to display the Radio button
in relation to the table cell in which it will be rendered.
-
: Choose the template to be used for the label.
-
Click Next.
5.
On the Source page:
-
: Choose the source for where the value is being set
from. It is normal to leave this set to Static Assignment where
value equals source attribute. What that means is when the page
is rendered the selected item will be set to the value
corresponding with the session state for the page item.
-
: Enter the value that for the radio group. This
value could be any of the values but make sure to use the result
and not the display value.
-
Click the Create Item button to not set
any conditions, or click Next to set conditions.
6.
On the Cachingpage, select
the desired Derive Item Source
option. The default is Only when the value is NULL.
7.
Click the Create Item button.
At this point, the radio group is not quite
finished. Running the page will show that the radio group displays in
a single column shown in Figure 10.30, which is not quite the desired
result. The reason that it is in a single column is because the item
creation wizard did not give the option necessary to have the values
in a single line. The item will have to be edited and a value
changed.
First, edit the page item, P3_COLORS, or whatever
you named it. A change needs to be made in the LOV definition for the
COLUMNS field. This field specifies in how many columns across the
display values should appear. In this case, the goal is to have a
single line, so the value will be changed to six. For two lines of
values, three columns would be used.
On display, the page item can be set to equal a
value. When the page is rendered, the display value corresponding to
the item value will be shown as chosen. For example, if P3_COLORS
have the value of W, when the page is rendered, White will be chosen.
Radio groups are great way to display a full list
to the user and have them select only a single value. Remember, to
limit the choices to only a few because it may take up quite a bit of
space on the page.
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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