Creating Custom Forms Part B Eyad Alshareef Edited

Creating Custom Forms Part B Eyad Alshareef, Edited by: Mostafa Ali 1

Lesson B Objectives After completing this lesson, you should be able to: n Suppress default system messages n Create alerts and messages to provide system feedback to users n Create applications that avoid user errors n Trap common runtime errors Eyad Alshareef, Edited by: Mostafa Ali 2

Controlling System Messages n Forms Services message line Displays FRM- and ORA- messages n Classified according to n n Severity n Whether n or not they require user intervention Suppress default system messages Replace with custom messages n Set : SYSTEM. MESSAGE_LEVEL variable n n In PRE-FORM trigger Eyad Alshareef, Edited by: Mostafa Ali 3

Oracle Error Message Severity Levels 5: informative message (one record saved) n 10: informative message advising user of procedural error (cannot insert character ) n 20: condition that keeps trigger from working correctly n 25 condition that keeps form from working correctly n >25: extreme severity (out of memeory) n Eyad Alshareef, Edited by: Mostafa Ali 4

Providing System Feedback n Important application design principle n n Provide users with feedback about what is happening in application Make applications forgiving n Allow users to undo unintended operations Eyad Alshareef, Edited by: Mostafa Ali 5

Suppressing Lower Level System Messages n Set : SYSTEM. MESSAGE_LEVEL variable to a higher level in PRE-FORM trigger : SYSTEM. MESSAGE_LEVEL : = 25; Eyad Alshareef, Edited by: Mostafa Ali 6

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 Eyad Alshareef, Edited by: Mostafa Ali 7

Messages n Syntax: MESSAGE(‘message text’); Message Eyad Alshareef, Edited by: Mostafa Ali 8

Custom Messages n Short text string that displayed on form message line n n Up to 200 characters Syntax: n MESSAGE('message_string'); Eyad Alshareef, Edited by: Mostafa Ali 9

Alerts Form-level object n Object properties define alert appearance n Message Title Style icon Buttons Eyad Alshareef, Edited by: Mostafa Ali 10

Alerts n Dialog box Display text message longer than 200 characters n Displays one or more buttons n n Allow user to select between alternatives that execute associated program statements n Top-level form object Eyad Alshareef, Edited by: Mostafa Ali 11

Alerts (continued) n Styles: Note n Caution n Stop n n Button Label property determines: How many buttons appear on alert n Labels on buttons n Maximum 3 buttons n Eyad Alshareef, Edited by: Mostafa Ali 12

Alerts (continued) Create alert from Alert Navigation node n To declare/display alert: n DECLARE alert_button NUMBER; BEGIN alert_button: = SHOW_ALERT('alert_name'); END; Eyad Alshareef, Edited by: Mostafa Ali 13

Example Alert Eyad Alshareef, Edited by: Mostafa Ali 14

Syntax to Display an Alert and Execute Alternate Commands Depending on the Button the User Clicked Eyad Alshareef, Edited by: Mostafa Ali 15

Avoiding User Errors n Help users avoid errors Configure forms that validate input values n Programmatically disable form command buttons n Disable navigation form text items containing values that users should not change n Eyad Alshareef, Edited by: Mostafa Ali 16

Validating Form Input Values n Validate input values Ensure that values meet specific preset requirements n Use n n Text item validation properties n Form validation triggers n Validation unit n Represents largest chunk of data that user can enter before form validates all input values Eyad Alshareef, Edited by: Mostafa Ali 17

Text Item Validation Properties Eyad Alshareef, Edited by: Mostafa Ali 18

Validating Form Input Values (continued) n Item validation trigger Item-level trigger n Associate with item’s WHEN-VALIDATE-ITEM event n Fires when item validated n n As n determined by form validation unit If not valid n Raises built-in exception named FORM_TRIGGER_FAILURE Eyad Alshareef, Edited by: Mostafa Ali 19

Disabling Form Command Buttons to Avoid User Errors n Enable or disable button while form running: n SET_ITEM_PROPERTY('item_name', property_name, property_value); Eyad Alshareef, Edited by: Mostafa Ali 20

Validation Triggers n When Validate Item It should be Item level trigger. n Executes when the item validation occurs depending on Validation Unit property. n E. g. : IF NOT : student. s_class IN (‘FR’, ’SO’) THEN Message(‘Legal Values are FR and SO); RAISE FORM_TRIGGER_FAILURE; END IF; n Eyad Alshareef, Edited by: Mostafa Ali 21

How To Disable Buttons SET_ITEM_PROPERTY n E. g. : SET_ITEM_PROPERTY(‘Control. Delete’ , ENABLED, PROPERTY_FALSE); n Eyad Alshareef, Edited by: Mostafa Ali 22

Disabling Text Item Navigation n Nonnavigable User cannot press Tab key to place insertion point in text item n Set item’s Keyboard Navigable property to No n User can still click mouse pointer in text item to enter value n n Create trigger that moves insertion point to another form item n WHEN-MOUSE-UP event Eyad Alshareef, Edited by: Mostafa Ali 23

Trapping Form Runtime Errors n ON-ERROR event occurs n n Whenever ORA- or FRM- error occurs while form running Create form-level trigger that corresponds to ON-ERROR event n Use decision control structure to handle different errors Eyad Alshareef, Edited by: Mostafa Ali 24

Forms Builder Built-in Procedures for Handling Errors Eyad Alshareef, Edited by: Mostafa Ali 25

Lesson C Objectives After completing this lesson, you should be able to: n Convert data blocks to control blocks n Link data blocks to control blocks n Create a form that has multiple canvases n Create tab canvases n Create stacked canvases Eyad Alshareef, Edited by: Mostafa Ali 26

Data Blocks vs. Control Blocks n Data block n n n Control block n n n Easy to create and use Is associated with a single table, and reflects the table’s structure 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 Eyad Alshareef, Edited by: Mostafa Ali 27

Converting a Data Block to a Control Block n Use Data Block and Layout Wizards to create data block form and form layout Convert data block to control block n Add command buttons to control form processing n Simplify creation of control blocks n Eyad Alshareef, Edited by: Mostafa Ali 28

Converting a Data Block to a Control Block n n 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: n n Database Data Block = No Then change the following text property: n Required = No Eyad Alshareef, Edited by: Mostafa Ali 29

Linking a Data Block to a Control Block n Create forms that link data blocks and control blocks to work together n Usually represent master-detail relationship Eyad Alshareef, Edited by: Mostafa Ali 30

Linking Data Blocks and Control Blocks 1. 2. 3. Create the control block as the master block Create the data block as the detail block, but do not create a master-detail relationship Create a master-detail relationship manually in the WHERE Clause property of the detail block: data_block_field = : control_block. text_item Eyad Alshareef, Edited by: Mostafa Ali 31

Creating the Data Block n Use Data Block Wizard and Layout Wizards To create and configure data block n Must contain field that links it to control block n Create data block without master-detail relationship n n Link two blocks later Eyad Alshareef, Edited by: Mostafa Ali 32

Linking the Control Block and the Data Block n Open detail data block’s Property Palette n n Modify data block’s WHERE Clause property General syntax: n fieldname : = control_block. text_item_name Eyad Alshareef, Edited by: Mostafa Ali 33

Displaying and Refreshing the Data Block Values n Create a trigger to: Place the insertion point in the data block GO_BLOCK(‘data_block_name’); n Flush the data block to make its data consistent with the master block and the database: EXECUTE_QUERY; n Eyad Alshareef, Edited by: Mostafa Ali 34

Refreshing the Data Block Values n Add commands to: Initially populate data block display n Periodically refresh data block records n n Use the GO_BLOCK built-in: n n To move form focus to data block Then execute EXECUTE_QUERY built-in Flushes block n Makes information consistent with corresponding database data n Eyad Alshareef, Edited by: Mostafa Ali 35

Creating Forms with Multiple Canvases Good practice not to show too much information on user’s screen display n Single-form approach n Create one form with multiple canvases n Enables form to share data among different canvases n Impossible for multiple programmers to work simultaneously on different canvases of same application n Eyad Alshareef, Edited by: Mostafa Ali 36

Creating a Form with Multiple Canvases Users should be able to see all canvas text items without scrolling n For complex applications with many text items, divide application into multiple canvases n Eyad Alshareef, Edited by: Mostafa Ali 37

Block Navigation Order First block in Object Navigator Data Blocks list determines block items that first appear when form opens n Users can use the Tab key to navigate among different block items n Canvas that contains block items automatically appears n Eyad Alshareef, Edited by: Mostafa Ali 38

Block Navigation Order Block order Canvas order doesn’t matter Eyad Alshareef, Edited by: Mostafa Ali 39

Working with Multiple Canvases and Data Blocks n Create form that contains multiple canvases Create individual canvases n Specify to display specific block items on specific canvas n n Create new data block n Select canvas name on which block items appear n On Layout Wizard Canvas page Eyad Alshareef, Edited by: Mostafa Ali 40

n Working with Multiple Canvases and Data Blocks (continued) Often forms that have multiple canvases also have multiple data blocks n Group items that appear on same canvas in single data block n To n n keep blocks small and manageable Cannot create two items that have same name in same data block Ensure that Forms Builder places new items in correct block Eyad Alshareef, Edited by: Mostafa Ali 41

Specifying the Block Navigation Order n Specify which canvas initially appears when user runs form Canvas whose block items appear first under Data Blocks node in Object Navigator window n Order of canvases in Object Navigator Canvases list does not matter n n Only order of data blocks Eyad Alshareef, Edited by: Mostafa Ali 42

Referencing Different Canvases, Form Blocks, and Block Items n All form items have Canvas property n Specifies name of canvas on which item appears Form always displays canvas on which item with focus appears n Execute GO_ITEM built-in n Move form focus to item on target canvas n Good practice to include block name n Eyad Alshareef, Edited by: Mostafa Ali 43

Tap Canvas Eyad Alshareef, Edited by: Mostafa Ali 44

Canvas n n It is the surface that has the form items on it. It has many types: n n n Content (The default) Tab Stacked … All canvases inside some window must have the property ‘Window’ has the name of the enclosing window. Eyad Alshareef, Edited by: Mostafa Ali 45

Tab Canvases n Multiple-page canvases that allow users to move among different canvas surfaces by clicking tabs Eyad Alshareef, Edited by: Mostafa Ali 46

Tab Canvas Components n Tab canvas n n Tab pages n n Surfaces that display form items Tab labels n n Collection of related tab pages Identifier at top of tab page A tab canvas lies on top of a content canvas Eyad Alshareef, Edited by: Mostafa Ali 47

Creating a Tab Canvas n Use the Tab Canvas tool on the Layout Editor tool palette to draw a tab canvas on an existing content canvas n By default, a new tab canvas has 2 tab pages Create new tab pages as needed n Adjust tab page properties n Eyad Alshareef, Edited by: Mostafa Ali 48

Important Tab Page Properties Name: how the page Is referenced in the form Label: Caption that appears on the associated tab Eyad Alshareef, Edited by: Mostafa Ali 49

Adjusting the Tab Page Order n 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 Eyad Alshareef, Edited by: Mostafa Ali 50

Creating and Configuring Tab Canvases in Forms n Tab canvases Multiple-page canvases n Allow users to move between multiple canvas surfaces n n By selecting tabs at top of canvas Display large number of related items in modular way n Direct user through sequence of steps for performing task n Eyad Alshareef, Edited by: Mostafa Ali 51

Creating a Tab Canvas Contains two or more tab pages n Tab page n Object representing surface n Displays form items n Has tab label identifier at top n Eyad Alshareef, Edited by: Mostafa Ali 52

Creating Form Items on a Tab Canvas Use tab pages as any content canvas n Create items on tab pages n Using Data Block Wizard n By creating control block and drawing text items directly on tab canvases n n Must be sure to specify placement of items on tab canvas Eyad Alshareef, Edited by: Mostafa Ali 53

Stacked Canvas Eyad Alshareef, Edited by: Mostafa Ali 54

Stacked Canvases Canvas that appears on an existing content canvas, and can be displayed or hidden as needed n Allows user to configure canvas items n Eyad Alshareef, Edited by: Mostafa Ali 55

Stacked Canvas Example Content canvas Stacked canvas Eyad Alshareef, Edited by: Mostafa Ali 56

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 n Create block items on the stacked canvas n Create buttons and triggers to display and hide the stacked canvas n Eyad Alshareef, Edited by: Mostafa Ali 57

Displaying and Hiding a Stacked Canvas n Displaying a stacked canvas: GO_BLOCK(‘stacked_canvas_block’); SHOW_VIEW(‘stacked_canvas’); n Hiding a stacked canvas: GO_BLOCK(‘content_canvas_block’); HIDE_VIEW(‘stacked_canvas’); Eyad Alshareef, Edited by: Mostafa Ali 58

Lesson C Summary Convert data block to control block n Create relationship between control block and data block n Display information on multiple canvases: n Single-form approach n Multiple-form approach n n Tab canvas n Multiple-page canvas Eyad Alshareef, Edited by: Mostafa Ali 59