Trees

Trees can be used to display hierarchal data.  Trees are based on a base table.  The table must have an ID column, a Parent ID column, and a display text item.  The following example uses the information in the following CAR_PARTS table.  A car is made up of parts and each part can have sub-parts.  The records that make up the CAR_PARTS table are shown in Table 11.2 and Figure 11.18.

Column Name	Data Type	Nullable	Default	Primary Key
ID	NUMBER	Yes	-	-
PARENT_ID	NUMBER	Yes	-	-
ITEM	varchar2(20)	Yes	-	-

When a tree is created, a new page is created with all the information required to display the tree.  A tree can be complicated to build.  It is recommended that the tree be created first in order to create the page.  Then, modify the page afterwards.

Creating a Tree

The first step to creating a tree is to navigate to the Shared Component area of the application.  Choose the Trees link in the second column.  This will start the Tree wizard.

1.     On the first page of the wizard, as shown in Figure 11.19, the following information is required.  All of these entries can be left at their default values.

• Page:  This is the number of that page which will be created

• Page Name:  Name of the page created.

• Region Template:  Template of the region which will display the tree.

• Region Name:  The name of the region. Click Next.

2.     The next page, shown in Figure 11.20, will require:

• Tree Name:  The name of the tree.  Enter in Car Parts.

• Default Expanded Levels:  This is how many levels the tree will show when first displayed.

• Start Tree:  The method to provide the starting point.  A Static Value will be used for the example.  Normally, this might be based on a LOV or other page item.  Click  Next.

3.      On the next page, as shown in Figure 11.21, the Tree template will be chosen.  Each tree still performs in the same manner; they just vary in the graphics which are shown in the tree.  The Standard Tree will be chosen for this example.  Click Next.

4.      On this page, shown in Figure 11.22, the starting point for the Tree, the root, will be specified.  This will be a static value, a query, or a popup value depending on what was selected on page two of the wizard, as was shown in Figure 11.20.  Enter the number zero (0).  Click Next.

5.      The next page of the wizard, shown in Figure 11.23, is to select which buttons to include with the Tree.  There are three buttons from which to choose: one to Collapse All nodes of the tree; one to Expand All nodes of the tree; and, one to Reset the tree to when it was first rendered.  Click Next.

6.      Using the next two pages, shown in Figure 11.24, of the wizard, the base table for the Tree will be chosen.  In this case, this will be the CAR_PARTS table.  The first page is where the Table Owner will be selected and the table itself will be selected on the second page.  Click Next.

7.      The next page, shown in Figure 11.25, is very important.  This is where the three columns which are required for a Tree will be specified: the ID; the PARENT ID; and, the LEAF NODE.  The link can be additional information on the part such as a picture and details.  In this example, a link will not be created.  Click Next.

8.      The next page is where optional WHERE and ORDER BY clauses can be specified for the Query.  Click Next.

9.      The summary page is last.  It will show all the options that were included in the wizard.  If all looks good, click Finish.

Creating Trees on Application Pages

A page will now be created.  When running the page, there will be a region with the tree.  If links were specified for the leaf nodes, each link could navigate to a new page.  The nodes can be collapsed or expanded by the user.  To learn more about the trees, look over the page that was created, as shown in Figure 11.26.