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The List Manager page item is a interesting type of item.  This type allows the user to enter values which will be added to a list.  Values can also be selected from a designated LOV to populate the list.  This type of item is good for information for which the user may not have direct knowledge.  For example, a person who is providing a list of email addresses to email something.  Since email addresses change all the time, it would be hard to keep up with a list.  With this item, the user can supply any unknown email addresses and also provide them with a list of known email addresses.  The next example will create a List Manager item just for this purpose.

Figure 10.27 shows an example of what this List Manager item will look like.  The top horizontal box is the entry box where the user will enter any unknown addresses.  After entering the address, the user will click on the Add button to add the entry to the list.  The lower vertical box will contain the entered items.  The user can remove items from the list by selecting the item in the list and pressing the Remove button.

There is a small icon next to the entry box.  This box will invoke the Popup LOV.  The LOV will provide a list of values to select.  The return value will be placed in the list.  The normal List Manager will convert everything to uppercase.  Use the type with preserve case to allow upper or lower case.

To create a List Manager 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 Manager that you would like and click Next.  The List Manager, based on Popup LOV, which preserves case, was chosen for the demonstration.  Table 10.3 shows the different type of List Managers available.

2.       On the Display Position and Name page.

• Item Name: Enter the name of the item, P1_EMAIL_ADDRESS.

• 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 most important part of the wizard.  This is where the display values and the results are defined for the list.  On this page, the developer will choose a LOV that has already be created and named, type in a new Select statement or make a Static list.  For this example, a named LOV which was previously created was chosen.  The SELECT statement for the LOV is:

select cust_last_name||', '||cust_first_name d, cust_email r
from  demo_customers
order by 1  

The PopUp LOV will show the customers name and when selected will return the customers email address back to the list.

The following are the explanations for some of fields on this page:

• Named LOV: Enter the name of the LOV that will provide the values for this select list.

• Display Null Option: Choose whether or not to display the fact that the session state for the item is NULL.

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 %.

• Null Text: 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.

• Null Value: 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:

•  Label: Enter the text to display next to the select list, Email Addresses.

• Label Alignment: Choose the position to place the label.

• Field Alignment: Select the position to display the select list in relation to the table cell in which it will be rendered.

• Label Template: Choose the template to be used for the label.

• Click Next.

     5.       On the Source page:

• Item Source: 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. 

• Default: For a certain value to be selected as the default, the value of the display item will be entered here.  This should be the same as the Null Value explained above.

• 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.

When the page is run, the List Manager item will start out empty.  Figure 10.28 gives an example of how the list looks after a few entries including an entry that is about to be added to the list.  The list box will expand and collapse based on the entries.

When the page is submitted, like the Multiple Select Lists, the page item will be set to the list values delimited by colons.  In this example, the page item will be equal to:

kent@yahoo.com:JohnDulles@aol.com:Eugene_Bradley@msn.com:Michael@dba.com

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