Enhanced Guide to Enhanced Guide to Oracle10gOracle10g

Chapter 6:Creating Custom Forms

Data Block and Custom Forms Data block form

Based on data blocks that are associated with specific database tables

Reflect the structure of the database Custom form

Based on control blocks that process data from multiple tables

Reflect business processes rather than the database structure

Creating a Custom Form

1. Create the form2. Create the form window and canvas

manually3. Create a control block

Data block that is not associated with a specific table

Contains form items that you manually draw on the canvas

4. Create form triggers to process data

Form Triggers Code that is associated with a form

object and an event Can contain SQL INSERT, UPDATE,

DELETE, and SELECT commands Referencing form text item values

in triggers:

:block_name.item_name

Program Units Self-contained programs Can be called from PL/SQL triggers Used to make triggers more

modular, and reuse code within triggers

Practice1 Create a custom form that has:

Employee Name Employee Salary Department Name

Create a LOV to retrieve block records Use triggers to retrieve block records Create a button that calls a program

unit to clear the block.

Referencing System Date and Time Values in FormsSystem Variable Return Value

$$DATE$$ Current operating system date

$$TIME$$ Current operating system time

$$DATETIME$$ Current operating system date & time

$$DBDATE$$ Current DB server date

$$DBTIME$$ Current DB server time

$$DBDATETIME$$ Current DB server date & time

Form Triggers Categories

Block processing Interface event Master-detail processing Message handling Navigational Query time Transactional Validation

Trigger Timing PRE-

Fires just before associated event occurs POST-

Fires just after associated event occurs ON-, WHEN-, KEY-

Fires immediately, in response to specific user actions, such as key presses

Trigger Scope Defines where an event must occur to

make the trigger fire Trigger scope includes the object to

which the trigger is attached, as well as all objects within that object Form-level: fires when event occurs within

any block or item in the form Block-level: fires when event occurs within

any item in the form Item-level: fires only when event occurs

within that item

Trigger Execution Hierarchy If 2 related objects have the same

trigger, the lower-level object’s trigger fires instead of the higher-level one. Form & block, block’s trigger fires Block & item, item’s trigger fires

You can specify a custom execution order using the Execution Hierarchy property of the trigger.

Navigational Triggers External navigation: occurs when

user causes form focus to change Internal navigation: occurs as a

result of internal form triggers that fire in response to external navigation events

User Action Triggers FiredResult on User Screen Display

User starts formPRE-FORMPRE-BLOCK

Form appears, but with no data visible

WHEN-NEW-FORM-INSTANCEWHEN-NEW-BLOCK-INSTANCEWHEN-NEW-RECORD-INSTANCEWHEN-NEW-ITEM-INSTANCE

Form is

available for use

Triggers That Fire at Form Startup

12 3

4 5

User Action Triggers Fired Result on User Screen Display

User places the insertion point in a text item

WHEN-NEW-ITEM-INSTANCE Insertion point appears in item

WHEN-NEW-RECORD-INSTANCE WHEN-NEW-ITEM-INSTANCE

Next record appears

User clicksthe Next Recordbutton

Triggers That Fire as a Result Of External Navigation

User Action Triggers FiredResult on User Screen Display

User closes the Forms Runtime window

Forms Runtime window closes

POST-BLOCKPOST-FORM

Triggers That Fire When a Form Closes

Practice2 Create a department data block. Create an Update button. Create a Cancel button that uses a

procedure.

Directing External Navigation Form tab

order is based on item order in Object Navigator block list

Formtaborder

Moving to a Specific Form Item GO_ITEM(‘block_name.item_name’); Do not write colon(:) before the block name in this commnd.

E.g: GO_ITEM(‘emp.sal’);

Other navigational instructions: GO_BLOCK(‘block_name’) GO_FORM(‘form_name’)

Oracle Error Message Severity Levels 5: informative message 10: informative message advising

user of procedural error 20: condition that keeps trigger

from working correctly 25 condition that keeps form from

working correctly >25: extreme severity

Suppressing Lower Level System Messages Set :SYSTEM.MESSAGE_LEVEL

variable to a higher level in PRE-FORM trigger

:SYSTEM.MESSAGE_LEVEL := 25;

Providing User Feedback in Forms

Message Text in message line at bottom of form Informational only; user doesn't have to

respond

Alert Dialog box Allows user to choose different ways to

proceed

Messages

Message

Syntax:MESSAGE(‘message text’);

Alerts Form-level object Object properties define alert

appearanceTitle

Styleicon

Message

Buttons

Code for Displaying an AlertDECLARE

alert_button NUMBER;

BEGIN

alert_button := SHOW_ALERT('alert_name');

IF alert_button = ALERT_BUTTON1 THEN

program statements for first button;

ELSE

program statements for second button;

END IF;

END;

Avoiding User Errors Make primary and foreign key

text items non-navigable (How?)

When user moves form focus to primary or foreign key text item, move focus to alternate form item (How?)

How to make nonnavigable item?

Set the text item property Keyboard Navigable to NO

Use When New Item Instance or

When Mouse Up triggers to make internal navigation from the nonnavigable item.

Trapping Runtime Errors Create an ON-ERROR event trigger

Form-level trigger Executes whenever an FRM- or ORA-

error occurs -FRM errors: generated by Forms

Runtime -ORA errors: generated by

database

Form Procedures That Return System Error Information DBMS_ERROR_CODE: The most

recent -ORA error number. (Negative Number)

DBMS_ERROR_TEXT: -ORA error message and number.

ERROR_CODE: The most recent FRM error number. (Positive Number)

ERROR_TEXT: FRM error message and number.

Structure of ON-ERROR Trigger

BEGIN --trap FRM errorsIF ERROR_CODE = FRM_error_code1 THEN

error handler;ELSIF ERROR_CODE = FRM_error_code2 THEN

error handler;…ELSE

--trap ORA errorsIF DBMS_ERROR_CODE = -ORA_error_code1 THEN

error handlerELSIF DBMS_ERROR_CODE = -ORA_error_code2 THEN

error handler…END IF

END IF;END;

Code totrap –FRM errors

Code totrap –ORA errors

Form Validation Ensures that form data meets

preset requirements so erroneous data is not sent to database

Using validation properties or using validation triggers.

Form Validation Categories Data

Specifies data types, lengths, and maximum and minimum values

Database Specifies which operations a user can

perform on a text item List of Values

Specifies whether a data value must be validated against the text item’s LOV (Validate From List text item property)

Validation Properties Validation unit form property:

specifies the largest data chunk that the user can enter before validation occurs Can be performed at the form, block,

record, or item level Specified in the Validation Unit property

on the form Property Palette By default, it is set to item level.

Cont. You should use the item level with

the custom forms, and the record or block level with the data block forms.

The validation properties that are checked always and before checking other properties and triggers are:

format mask, required, datatype, range, and validate from list

Text Item Validation Properties

Data Type Minimum Value Maximum Value Validate From List Insert Allowed Query Allowed Required …

Why do not we use validation properties instead of validation triggers?

Question

We use validation triggers for more complex validations. (like what?)

Answer

Validation Triggers When Validate Item

It should be Item level trigger. Executes when the item validation occurs

depending on Validation Unit property. E.g. : IF NOT :student.s_class IN (‘FR’,’SO’) THEN Message(‘Legal Values are FR and SO);RAISE FORM_TRIGGER_FAILURE;END IF;

How To Disable Buttons SET_ITEM_PROPERTY E.g. :SET_ITEM_PROPERTY(‘Control.Delete

’ , ENABLED, PROPERTY_FALSE);

Data Blocks vs. Control Blocks Data block

Easy to create and use Is associated with a single table, and reflects

the table’s structure Control block

Requires a lot of custom programming Can contain items from many different tables

You can link data and control blocks to take advantages of the strengths of each

Linking Data Blocks and Control Blocks

1. Create the control block as the master block2. Create the data block as the detail block,

but do not create a master-detail relationship

3. Create a master-detail relationship manually in the WHERE Clause property of the detail block:

data_block_field = :control_block.text_item

Displaying and Refreshing the Data Block Values Create a trigger to:

Place the insertion point in the data block

GO_BLOCK(‘data_block_name’); Flush the data block to make its data

consistent with the master block and the database:

EXECUTE_QUERY;

Example1. Create a text field manually and name it

dept_no. Name the block containing this field ‘control’.

2. Create a data block depending on the table ‘dept’. Make it tabular with 5 rows.

3. Go to the dept block property: Where Clause

And write in it:

Deptno = :control.dept_no

4. Make a button and write in it the previous code

5. Run the form, enter an existing department number in the dept_no field, and press the button.

Converting a Data Block to a Control Block Create a data block and layout that

contains most of the required text items Convert the data block to a control

block by changing the following block property: Database Data Block = No

Then change the following text property: Required = No

Creating a Form with Multiple Canvases Users should be able to see all

canvas text items without scrolling For complex applications with

many text items, divide application into multiple canvases

Block Navigation Order First block in Object Navigator Data

Blocks list determines block items that first appear when form opens

Users can use the Tab key to navigate among different block items

Canvas that contains block items automatically appears

Block Navigation Order

Block order

Canvas order doesn’t matter

Controlling Block Navigation Block Navigation Style property

Same Record: navigation cycles through items on same record when you reach the end of the current record.

Change Record: navigation moves to the next record in the same data block when you reach the end of the current record.

Change Data Block: navigation moves to next data block in list when you reach the end of the current block.

Canvas It is the surface that has the form items

on it. It has many types:

Content (The default) Tab Stacked …

All canvases inside some window must have the property ‘Window’ has the name of the enclosing window.

Tab Canvases Multiple-page canvases that allow

users to move among different canvas surfaces by clicking tabs

Tab Canvas Components Tab canvas

Collection of related tab pages Tab pages

Surfaces that display form items Tab labels

Identifier at top of tab page A tab canvas lies on top of a

content canvas

Creating a Tab Canvas Use the Tab Canvas tool on

the Layout Editor tool palette to draw a tab canvas on an existing content canvas By default, a new tab canvas has 2

tab pages Create new tab pages as needed Adjust tab page properties

Important Tab Page Properties

Name: how the pageIs referenced in the form

Label: Caption that appears on the associated tab

Adjusting the Tab Page Order Tab page that appears first is tab

page whose block items appear first in the Object Navigator

Block order

Tab page order doesn’t matter

Stacked Canvases Canvas that appears on an

existing content canvas, and can be displayed or hidden as needed

Allows user to configure canvas items

Stacked Canvas Example

Stackedcanvas

Contentcanvas

Creating a Stacked Canvas Use the Stacked Canvas tool on

the Layout Editor tool palette to draw a stacked canvas on an existing content canvas

Create block items on the stacked canvas

Create buttons and triggers to display and hide the stacked canvas

Displaying and Hiding a Stacked Canvas Displaying a stacked canvas:GO_BLOCK(‘stacked_canvas_block’);

SHOW_VIEW(‘stacked_canvas’);

Hiding a stacked canvas:GO_BLOCK(‘content_canvas_block’);

HIDE_VIEW(‘stacked_canvas’);

Practice What are the smart triggers? What is the message displayed on saving

successfully? What is the message displayed when you click

SAVE without making any operation? What is the message displayed when the

insertion (or deletion) operation fails? What is the message displayed when you

enter an incorrect data type in the field? What is the type of the previous messages?

(FRM or ORA)