About creating an AJAX page with DML procedures using dynamic actions

Question

About creating an AJAX page with DML procedures in APEX using dynamic actions. Help with limitations.
I want to share my experience, creating AJAX procedures in APEX 4.0.
LIMITATIONS
•     How Can I Hide UPDATE button while I press NEW button. ??
•     How Can I Hide CREATE button while I’m UPDATING A RECORD. ??
•     How can I avoid multiple Inserts or Updates. ??
Here are the steps to create an AJAX Updatable Form using the sample table DEPTS. You can see the demo here: [http://apex.oracle.com/pls/apex/f?p=15488:1]
1)     Create a blank page
2)     Add a Report Region for departments (It shows the columns deptno, dname and loc).
3)     Add an HTML Region and create the elements to edit a Department.
a.     P1_DEPTNO (Hidden to store PK)
b.     P1_DNAME (Text Field)
c.     P1_LOC (Text Field)
4)     You also have to create a hidden element called P1_ACTION. This will help to trigger dynamic actions to perform DMLs.
5)     Open Page Attributes and in the HTML Header Section include the following code.
<script>
     function doSelect(pId){
          $x_Value(‘P1_DEPTNO’,pId);
          $x_Value(‘P1_ACTION’,’SELECT’);
</script>
6)     Modify the column DEPTNO in the report, to add column link. In the link text you can use #DEPTNO# , in target you must select ‘URL ‘ and in the URL field write javascript:doSelect(#DEPTNO#);
7)     Create the following Buttons in the Form Region.
CANCEL     Redirects to URL: javascript:$x_Value(‘P150_ACTION’,’CANCEL’);
NEW          Redirects to URL: javascript:$x_Value(‘P150_ACTION’,’NEW’);
SAVE          Redirects to URL: javascript:$x_Value(‘P150_ACTION’,’UPDATE’);
CREATE          Redirects to URL: javascript:$x_Value(‘P150_ACTION’,’CREATE’);
8)     Create the following Dynamic Action to Select a Department
Name:     Select Dept
Event:     Change
Selection Type:     Item(s)
Item(s):     P1_ACTION
Condition:     equal to
Value:     SELECT
Action:     Execute PL/SQL Code
PL/SQL Code:     
SELECT dname, loc
INTO :P1_DNAME, :P1_LOC
FROM dept
WHERE deptno = :P1_DEPTNO;
Page Items to Submit:     P1_DEPTNO, P1_DNAME, P1_LOC     
Don’t include any false action and create the Dynamic Action.
The first limitation, the value of page elements don’t do refresh so I added the following true actions to the dynamic action AFTER Execute PL/SQL Code.
Action:     Set Value
Unmark *‘Fire on page load’* and *‘Stop execution on error’*
Set Type:     PL/SQL Expression
PL/SQL Expression:     :P1_DNAME
Page Items to submit:     (none) (leave it blank)
Affected Elements: Item P1_DNAME
Action:     Set Value
Unmark *‘Fire on page load’* and *‘Stop execution on error’*
Set Type:     PL/SQL Expression
PL/SQL Expression:     :P1_LOC
Page Items to submit:     (none) (leave it blank)
Affected Elements: Item P1_LOC
These actions allow refresh the items display value.
9)     Create the following Dynamic Action to Update a Department
Name:     Update Dept
Event:     Change
Selection Type:     Item(s)
Item(s):     P1_ACTION
Condition:     equal to
Value:     CREATE
Action:     Execute PL/SQL Code
PL/SQL Code:     
UPDATE dept SET
dname = :P1_DNAME,
loc = :P1_LOC
WHERE deptno = :P1_DEPTNO;
Page Items to Submit:     P1_DEPTNO, P1_DNAME, P1_LOC     
Don’t include any false action and create the Dynamic Action.
Include the following True Actions BEFORE the Execute PL/SQL Code true Action.
Action:     Set Value
Unmark ‘Fire on page load’ and ‘Stop execution on error’
Set Type:     PL/SQL Expression
PL/SQL Expression:     :P1_DNAME
Page Items to submit:     P1_DNAME
Affected Elements: Item P1_DNAME
Action:     Set Value
Unmark *‘Fire on page load’* and *‘Stop execution on error’*
Set Type:     PL/SQL Expression
PL/SQL Expression:     :P1_LOC
Page Items to submit:     P1_LOC
Affected Elements: Item P1_LOC
These actions allow refresh the items display value.
Finally to refresh the Departments report, add the following true action at the end
Action:     Refresh
Affected Elements: Region Departments
10)     Create the following Dynamic Action to Create a Department
Name:     Create Dept
Event:     Change
Selection Type:     Item(s)
Item(s):     P1_ACTION
Condition:     equal to
Value:     CREATE
Action:     Execute PL/SQL Code
PL/SQL Code:     
INSERT INTO dept(deptno,dname,loc)
VALUES (:P1_DEPTNO,:P1_DNAME,:P1_LOC);
Page Items to Submit:     P1_DEPTNO, P1_DNAME, P1_LOC     
Don’t include any false action and create the Dynamic Action.
Include the following True Actions BEFORE the Execute PL/SQL Code true Action.
Action:     Set Value
Unmark *‘Fire on page load’* and *‘Stop execution on error’*
Set Type:     PL/SQL Function Body
PL/SQL Function Body:     
DECLARE
v_pk NUMBER;
BEGIN
SELECT DEPT_SEQ.nextval INTO v_pk FROM DUAL;; -- or any other existing sequence
RETURN v_pk;
END;
Page Items to submit:     P1_DEPTNO
Affected Elements: Item P1_DEPTNO
Action:     Set Value
Unmark *‘Fire on page load’* and *‘Stop execution on error’*
Set Type:     PL/SQL Expression
PL/SQL Expression:     :P1_DNAME
Page Items to submit:     P1_DNAME
Affected Elements: Item P1_DNAME
Action:     Set Value
Unmark ‘Fire on page load’ and ‘Stop execution on error’
Set Type:     PL/SQL Expression
PL/SQL Expression:     :P1_LOC
Page Items to submit:     P1_LOC
Affected Elements: Item P1_LOC
These actions allow refresh the items display value.
Finally to refresh the Departments report, add the following true action at the end
Action:     Refresh
Affected Elements: Region Departments
11)     Create the following Dynamic Action to delete a department
Name:     Delete Dept
Event:     Change
Selection Type:     Item(s)
Item(s):     P1_ACTION
Condition:     equal to
Value:     DELETE
Action:     Execute PL/SQL Code
PL/SQL Code:     
DELETE dept
WHERE deptno = :P1_DEPTNO;
Page Items to Submit:     P1_DEPTNO
Don’t include any false action and create the Dynamic Action.
Include the following True Actions AFTER the Execute PL/SQL Code true Action.
Action:     Refresh
Affected Elements: Region Departments
Action:     Clear
Unmark ‘Fire on page load’
Affected Elements: Items P1_DEPTNO, P1_DNAME, P1_LOC
12)     Finally Create the following Dynamic Action for the NEW event
Name:     New Dept
Event:     Change
Selection Type:     Item(s)
Item(s):     P1_ACTION
Condition:     equal to
Value:     NEW
Action:     Clear
Unmark *‘Fire on page load’*
Affected Elements: Items P1_DEPTNO, P1_DNAME, P1_LOC

Answer 1

I need some help to solve this issues
•     How Can I Hide UPDATE button while I press NEW button. ??
•     How Can I Hide CREATE button while I’m UPDATING A RECORD. ??
•     How can I avoid multiple Inserts or Updates. ??