Event Sequence in Visual FoxPro

Article
07/09/2007

Though some events occur as single events, a user action often triggers multiple events. Some of these events occur independently; however, some event sequences are fixed, for example, the event sequence that occurs when a form is created or destroyed.

When a sequence of events is triggered for a control, the entire sequence of events is associated with the control. For example, suppose you click the left mouse button on a command button and the drag the mouse pointer away from the command button. The command button's MouseMove event continues to occur even though the mouse pointer moves over the form. If you release the left mouse button over the form instead of over the command button, the MouseUp event that occurs is associated with the command button instead of the form.

The following table shows the general sequence of Visual FoxPro events, assuming that the data environment's AutoOpenTables property is set to True (.T.). Other events can occur based on user interaction and system response.

Visual FoxPro Event Sequence

Object	Event that occurs
Data environment	BeforeOpenTables
Form set	Load
Form	Load
Data environment cursor(s)	Init
Data environment	Init
Objects 1	Init
Form	Init
Form set	Init
Form set	Activate
Form	Activate
Object1 2	When
Form	GotFocus
Object1	GotFocus
Object1	Message
Object1	Valid 3
Object1	LostFocus
Object2 3	When
Object2	GotFocus
Object2	Message
Object2	Valid 4
Object2	LostFocus
Form	QueryUnload
Form	Destroy
Object 5	Destroy
Form	Unload
Form set	Unload
Data environment	AfterCloseTables
Data environment	Destroy
Data environment cursor(s)	Destroy

1. For each object, from innermost object to outermost container 2. First object in the tab order 3. Next object to get focus 4. As the object loses focus 5.For each object, from outermost container to innermost object

Event Sequence Example

The following example uses a form to illustrate the order in which events occur in response to user interaction.

A sample form

FoxProFormEvenSequence screenshot

In this example, the user performs the following actions:

Runs the form.
Types text in the Text1 text box.
Selects the text and copies it to the Clipboard.
Moves to the Text2 text box by pressing the TAB key.
Pastes the text into Text2.
Closes the form by clicking the Command2 command button.

These actions trigger system events for each object. The following tables list the events that occur in response to each user action.

Note

In this example, the Paint event has been removed from the tables because this event occurs frequently and makes it difficult to see the sequences of the other events.

Action 1

The user runs the form by typing the following command in the Command window:

DO FORM form1 NAME frmObject

Visual FoxPro loads the form, initializes each object, and then initializes the form. The form is activated and the first text box receives input focus.

Object	Event
DataEnvironment	BeforeOpenTables
Form1	Load
DataEnvironment	Init
Text1	Init
Text2	Init
Command1	Init
Command2	Init
Form1	Init
Form1	Activate
Form1	GotFocus
Text1	When
Text1	GotFocus

Action 2

The user types the text "Test" in the text box, Text1. Each keystroke generates two events.

Note

The KeyPress event receives two parameters: a number representing the pressed key and the state of the SHIFT, ALT, and CTRL keys.

Object	Event	Parameters
Text1	KeyPress	(84 for "T", 1)
Text1	InteractiveChange
Text1	KeyPress	(101 for "e", 0)
Text1	InteractiveChange
Text1	KeyPress	(115 for "s", 0)
Text1	InteractiveChange
Text1	KeyPress	(116 for "t",0)
Text1	InteractiveChange

Action 3

The user selects the text in the text box, Text1, by double-clicking the text and copies the text to the Clipboard by pressing CTRL+C. Mouse events and a Click event accompany the DblClick event.

Note

The MouseMove, MouseDown, and MouseUp events receive four parameters: a number indicating the pressed button, the state of the SHIFT key, and (X, Y) coordinates. The X and Y coordinates are relative to the form and reflect the form's scale mode, for example, pixels. Though only one MouseMove event is listed for each control, in actuality, this event can occur half a dozen times or more.

Object	Event	Parameters
Form1	MouseMove	(0, 0, 100, 35)
Text1	MouseMove	(0, 0, 44, 22)
Text1	MouseDown	(1, 0, 44, 22)
Text1	MouseUp	(1, 0, 44, 22)
Text1	Click
Text1	MouseDown	(1, 0, 44, 22)
Text1	MouseUp	(1, 0, 44, 22)
Text1	DblClick

Action 4

The user moves to the text box, Text2, by pressing the TAB key.

Object	Event	Parameters
Text1	KeyPress	(9, 0)
Text1	Valid
Text1	LostFocus
Text2	When
Text2	GotFocus

Action 5

The user pastes the text into the text box, Text2, by pressing CTRL+V.

Object	Event
Text2	InteractiveChange

Action 6

The user clicks the command button, Command2, to close the form.

Object	Event
Form1	MouseMove
Command2	MouseMove
Text2	Valid
Command2	When
Text2	LostFocus
Command2	GotFocus
Command2	MouseDown	(1, 0, 143, 128)
Command2	MouseUp	(1, 0, 143, 128)
Command2	Click
Command2	Valid
Command2	When

When the form closes and objects are released, additional events take place in the opposite order of the events listed for Action 1.

Object	Event
Form1	Destroy
Command2	Destroy
Command1	Destroy
Text2	Destroy
Text1	Destroy
Form1	Unload
DataEnvironment	AfterCloseTables
DataEnvironment	Destroy

Event Sequence in Visual FoxPro

Event Sequence Example

See Also

Tasks

Concepts

Other Resources

Additional resources