Session #
An Introduction to Controls
Rainer Becker
dFPUG / ISYS GmbH
Controls.doc 37 KB
Controls.ppt 129KB
Introduction
Abouüt the Speaker
Rainer Becker is the leader of the German FoxPro User Group, an organisation
with 1100+ paying members (companies and programmers), and the president
of the ISYS GmbH, a MS Solution Provider and contract partner of MS Consulting
Services. You can reach him at:
Adress: Rainer Becker, Messerschmittstr. 2a,
65760 Eschborn, Germany
Phone: 01149-6173-68182, Fax: -65997
But better you try it via CompuServe (CIS-ID 100024,1364) or leave a
message at the dFPUG-section (GO MSCESYS).
Whats included
We will start with a short introduction to the principles of Properties,
Events and Methods. You need to know these terms to work with controls
of any kind.
The main part is a guided tour through all Controls. We will visit old,
new and changed ones in a sorted order - walking all properties upstairs.
The controls are sorted by the number of properties, events and methods
they have bringing us some new of each by each new control we see.
Finally I will loose some words about containers, naming conventions
and the use of Builders as well as guide you to some sessions that build
on this one.
Whats excluded
We can not talk (at least not to much) about the following themes in
Visual FoxPro:
Form Designer
Class Designer
Grid-Control
OLE-Controls
Classes
Inheritance
Non-Visual Objects
Event-Model
But you might get a good base for all of that with this session as you
should have a good overview over all types of controls.
Vocabulary
Visual FoxPro introduces a lot of new buzz-words. Some of them are really
important when you start working with controls. These are properties,
events and methods. All three are not that exactly defined and overlap
sometimes. The questions we need to answer in the beginning:
- What are Properties ?
- What are Methods ?
- What are Events ?
- How to avoid confusion?
- How to reference objects ?
What are PROPERTIES?
In FoxPro/Windows we had private and public variables. In Visual FoxPro
there are some more type of variables. Additionaly all types of controls
have properties - think of them as variables bound to a control. Some
examples:
commandbutton.caption = text shown on the button
textbox.comment = a note of the developer
Even better might be this description: Public vars with a private path
as you can access properties from everywhere as long as you know where
they live.
You can add your own properties to a control! Later on you will need
them. You can use them for non-visual objects or even applications-objects.
What are METHODS?
Methods are procedures. Think of them as old-style snippets, saved in
a memo-field and compiled when you close the memo. They are proceduress
bound to Controls/Forms instead staying in an individual program (or generated
screen-file).
Some Examples:
Refresh Repaint the object
SetFocus Make object the current object
Even better might be this description: Public functions with a private
path as you can access methods from everywhere as long as you know where
they live. Might remind you to the construct DO <function> IN.
You can add your own methods as you can add properties. You will sometimes
need your own methods. Building your own is real fun as you can really
encapsulate code with the object and e.g. build protected invisible internal
methods that can only seen and used be the object itself.
What are EVEN3TS?
Events occur outside of program control and the application has to react
to them - at least if it is an event-driven application. In connection
with controls, events are bound to methods. Therefore you can think of
them as old-style snippets called when something happened. They are procedures
bound to Windows-Events.
Some Examples:
VALID old-fashioned VALID-event
CLICK a mouse-click happened on a control
You can not extend the available set of events. Think of events as a
fixed set of methods that are bound to the operating system events, internal
events of Visual FoxPro (like a Timer event) or an action of the user
(like a mouse-click or mouse-move).
You normally need only some of them - but it is great that there are
so many! In most controls nearly all events are left blank except for
e.g. the click-event.
Avoid Confusion
As there are a lot of properties, methods and events you can easily get
confused. Do not do that <g>. Just remember that both, Events and
Methods, have a Procedure that can be called. In case of methods it is
only called by your code, in case of events these procedures can be called
from someone else additionaly. By the way: Therefore sometimes code that
should be placed in an event is put into a separate method and called
from the event instead, to ease access.
Events could also be seen as an regular Event that occured and a Method
bound to that event. On the other hand some properties are followed by
actions (and can be seen as events too).
These Categories are not closed boxes, do not loose to much time to distinguish
events and methods. There are many - but most are easy to use! Do not
get confused by the sheer mass of things you see in the property sheet.
When dealing with the property sheet and all these properties, events
and methods you should obey the graphical hints Visual FoxPro provides.
· Bold = changed
· Italic = read-only
If you switch a property and aftterwards switch it back to ist default
value it is still marked in bold. Use RESET TO DEFAULT (located on the
menu of the right mouse button) to get rid of unwanted changes. This sets
back the original graphical hints.
Syntax
As mentionend above you can access all properties of all controls by
a special access path. The syntax definition for accessing them:
objectvariable.[form.]control.property = Setting
As the hierarchy of controls can end up with a very long list, there
are some shurtcuts implemented:
THIS. the actual control
THISFORM. the actual form
THISFORMSET. the actual formset
_SCREEN. the FoxPro main window
ACTIVEFORM. the active form of a form set
ACTIVEPAGE. the active page of a page frame
ACTIVECONTROL. the active control on a container
PARENT. the parent object (not
inheritance!)
The THIS-shortcuts can only be used within methods.
The ACTIVE-shortcuts are connected to a logical property of the control
- you can cycle through this property in all associated controls to find
inactive ones.
The keyword PARENT. should be fully understood. It has got nothing to
do with the inheritance or the parent class (see below). It is just the
object in which the control resides. In case of a option button the parent
is the optino button group. If a command button is placed on a form the
form is the parent, if it is placed in a command button group the group
is the parent. This keyword is extremly usefull if you build a group of
controls that belong together. If you reference the connected objects
via PARENT. you never need to know who the parent (Allis?) is.
To short writing of references you can use the construct WITH.. ..ENDWITH
for a group of properties to be used with the same reference.
If you do not know the childs of a container object, there are clauses
like COUNT or PAGES that behave like arrays of the child objects and can
be used to reference all of them or a special one by adding a number in
a bracket.
Controls - A Guided Tour
Here is the list of controls
we will visit in this order:
- Timers
- Lines
- Shapes
- Images
- Labels
- Command Buttons
- Option Buttons
- Check Boxes
- Text Boxes
- Edit Boxes
- Spinners
- Option Groups and Command Groups
- Combo Boxes
- List Boxes
- Page Frames
- Pages
- OLE-Controls
Not all of them are new! Most of them are renamed. Here is the list of
renamed controls:
Text => Label control
GET-Field => Text box
Edit Region => Edit box
Popup => Combo box
Radio button => Option button
Screen => Form
ScreenSet => FormSet
Picture => Image
Really new are:
Timers => for timed events (at
least a small help)
Pages/Pageframe => for these nice tabbed dialogs
Grid => the all-new-version of the browse-command
Basic Example
Lets start with a new but small one: Timers
Data Comment, Tag
Methods BASIC, TimerEvent, Reset
Layout COORDINATES
Other CLASS, Interval
Tips Not executed while Menu open
Not exact enough for RealTime
special Timer Property/Event/Method
IntervalProp. Timer in milliseconds
TimerEvent Procedure called at Event
ResetMethod Restart timer
Basic Data
Comment You should use it!
Tag Free property
Basic Layout
Top ...
Left ...
Heigth ...
Width ...
Basic Other
Name Naming conventions
Enabled logical Flag
Class Objects belong to classes
ClassLibrary optional: VCX of the class
Baseclass Base class derived from
Parentclass optional: derived from
Parent runtime: container object
Basic Events
Init Object initialised
Destroy Object removed
Error local error-handler
Basic Methods
CloneObject runtime duplication
SaveAsClass objects from VCX to VCX
ReadExpression Method at design time
WriteExpression Method at design time
Visible Objects
Lines
Data ---
Events CLICK, MOUSE, DRAG
Methods Drag, Move, UIEnable, ZOrder
Layout DragIcon/Mode, BORDER,
Draw- Mode, MousePointer, LineSlant
Other HelpContextID
Tips No 3D-line-effects
Click Events for visible Objects
Click Mouse left click
DblClick Mouse double click
RightClick Mouse right click
Mouse Events for visible Objects
MouseMove Mouse over object
MouseDown Mouse pressed for click
MouseUp Mouse released
MousePointer 12 pointer versions
Drag & Drop for visible Objects
Drag
DragDrop End of drag, target event
DragOver object over target, target event
Methods
Drag Method for manual dragging
Move Method for manual moving
Properties
DragIcon Cursor Icon for drag
DragMode automatic / manual
Properties for Visible Objects
Bordercolor
Borderstyle
Borderwidth
Visible Temporary hide object
HelpContextID for HelpCompiler
ZOrder Meth. active Page, tlb order
UIEnable Evt. Page activate event
Drawmode 16 different modes
(Line/Shape/Form)
LineSlant special line property
Plain Objects
Shapes
Data ---
Methods ---
Layout BackColor/Style, FillColor/Style
ColorScheme/Source, ToolTip;
SpecialEffect, Curvature
Other ---
Tips Shapes in front block the click event
Properties for Plain Objects
Colors
BackStyle Transparent / Opaque (Default)
BackColor RGB-Color for Qpaque objects
FillColorStyle Transparent, Solid, Lines
FillColor RGB-Color if not transparent
ColorScheme Object/Form/Source/Default
ColorSource Scheme for Above=Source
ToolTipText ToolTip if Form.ShowTips=.T.
SpecialEffect Plain or 3D
Curvature 0=rectangle - 99=circle
Images
Data ---
Methods ---
Layout Picture (Bitmap, Icon)
Stretch (Clip/Isometric/Stretch)
Other ---
Tips Stretch also used for OLE
Objects with Caption
Labels
Data ---
Methods ---
Layout Caption, FONT, COLOR,
AutoSize, WordWrap, Alignment
Other --
Tips The Caption can be a function
Layout Properties for Objects with Caption
FontName Fontname
FontSize Fontsize
FontFlags FontBold, FontItalic, FontStrikeThru,
FontOutline, FontUnderline, FontShadow
DisabledBackColor Color
DisabledForeColor Color
ForeColor Color
Caption Text to be shown (function)
Alignment Left/Right/Centered
AutoSize Resize horiz. for text
WordWrap Wrap words/resize vertical
Accessible Objects
Command Buttons
Data TerminateRead
Methods ErrorMessage, see EVENTS
Layout DownPicture, DisabledPicture
StatusBarText, (Style=Inv.)
Other TabIndex, TabStop (Forms!)
Default, Cancel
Tips Use small fonts with pictures Use
StatusBarText instead
Events for accessible objects
When old-fashioned WHEN
Valid old-fashioned VALID
GotFocus Tabbed to it
LostFocus Tabbed somewhere else...
SetFocus Method (enabled & visible)
KeyPress Key Preview Event
Refresh SHOW GET (Requery,Page)
Message Return Message text (Old!)
Option Buttons
Data ControlSource
Field or memvar
Value
same type as ControlSource
Methods ---
Layout Alignment (Left/Right) for button
SpecialEffect not for command
button
Other ---
Tips Only in Option Button Groups!
Avoid Confusion
Name object name
Caption title
ControlSource differs
memvar
field
function
Value object value
Check Boxes
Data ---
Methods InteractiveChangeEvent P rogrammaticChangeEvent
Layout ---
Other ---
Tips ProgrammaticChange important!
Objects with entered data
Text Boxes
Data Format, InputMask, Margin, Read-Only,
Open/MemoWindow
Methods RangeHigh, RangeLow
Layout SELECT, Style (SAY-compatible), PasswordChar
Other HideSelection
Tips - Play with selected areas!
Selected Text
SelStart Begin of selection
SelLength Number of chars
SelText Complete Selected text
HideSelection Show after LostFocus
SelectedForeColor Text color
SelectedBackColor Background color
Edit Boxes
Data MaxLength
Methods ---
Layout ScrollBars (vert. & horiz.)
Other AllowTabs
Tips - „Selected text“ applies here
Spinners
Data KeyboardHigh/LowValue, SpinnerHigh/LowValue,
Increment
Methods UpEvent, DownEvent
Layout ---
Other ---
Tips - Use High/LowValues
instead of RangeEvents
Combo and List boxes
Combo Boxes
Data BoundColumn, DisplayValue
Methods AddItem, AddListItem,
Layout ColumnCount, -Lines,
-Width,
Disabled/Select/Item/Back/ForeColor
Other TopIndex, TopItemID,
+NEW
IncrementalSearch,
Listcount,ListIndex, ListIdemID
Layout for Combo box
ColumnCount Number of Columns
ColumnLines Show column lines
ColumnWidth Width of columns (colon-delimited)
ItemBackColor
ItemForeColor
SelectedItemBackColor
SelectedItemForeColor
DisabledItemBackColor
DisabledItemForeColor
Data for Combo box
RowSourceType 9 options
RowSource name type
BoundColumn Column bound to Value
DisplayValue Text or pos. for display
ItemData Additional value
List Array of text
Sorted Alphabetically sorted
FirstElement for Arrays only
NumberOfElements for Arrays only
Methods for Combo box
Requery Requery SQL/QPR-Source
Other for Combo box
IncrementalSearch self-explanatory
TopIndex first visible item
NewIndex last AddItem-position
Listcount Number of items
ListIndex (Last) selected
item
What are Ids?
ItemIDData Additional value by ID
ListItem Array of text by ID
Other
TopItemID ID of topmost vis. list-item
NewItemID last AddItem-ID
ListItemID (Last) selected item ID
Do not get confused by the pairs List / ListItem and ListIndex / ListItemID!
The RowSourceType (0=None), (1=Value)
ID-Methods in a Combo box
AddItem Add at position
AddListItem Add with ID
RemoveItem Remove from position
RemoveListItem Remove with ID
Clear Delete all items
IndexToItemID Position -> ID
ItemIDToIndex ID -> Position
List Boxes
Data ---
Methods ---
Layout ---
Other MultiSelect
Tips Use DisplayValue
and Value together for text and offset
Container
Container hierarchy
FormSet Form
Form Pageframe, Grid, Controls
PageFrame Pages
Page Grid, Controls
Grid Columns
Column Header, Controls
Option Group Option Buttons
Command Group Command Buttons
Option/Command Button Groups
Data ---
Methods AddObject, RemoveObject
Layout ButtonCount
Other Buttons
Tips ChangeEvents only
in Groups
No Inheritance
for new buttons
Page Frames
Data ActivePage
Methods ---
Layout PageCount, PageHeight/Width,Tabs,
TabStretch
Other Pages (Array)
Tips Drop objects on top
for all pages
Pages
Data Controls (Array)
Methods ---
Layout ControlCount
Other PageOrder, KeyPreview
Tips - Reference all with
PAGES
Grids
As Grids are the most complex controls you can have, an own session is
donated to them. Most important for you to know is, that a Grid is a container
that can consist of Headers and Columns. Columns are containers too as
they consist of e.g. text objects or other types of controls. It is really
complicated to build a Grid by hand or programmatically. You should start
building grids on your own with the help of the Grid Builder - otherwise
it will be real pain. The best might be to have a look at the Session
„Using the Grid Control“ from Whil Hentzen.
OLE-Controls
There are two type of OLE-controls. First you have OLE Bound Controls
which are "bound" to Genearl-fields and have no own Events.
Second you have OLE Container Controls which are an OCX with own Events
connected to it or an other OLE not bound to fields. The OCX-libraries
are new to the FoxPro world and give us the power VisualBasic-users had
with the old-fashioned VBX-libraries. Have a look at the Session „OLE
Custom Controls“ from Steven Black, who will introduce you a lot of never-seen
(at least in the FoxPro world) controls you can buy at the fast growing
Third-Party-market.
Container-Confusion
To avoid container-confusion, you need to distinguish three types of
controls, that might contain other controls.
- Container Objects The official visual
container control type:
FrameSet, Frame, PageFrame, Page, Grid,
Column, Option Group, Command Group
- Control Objects A container
with protected objects in it
- Custom Objects A non-visual-class
that might contain other objects
Some tips and hints
Ease your work with Naming Conventions
If you have not worked with naming conventions, switching to Visual FoxPro
is a good point to start with it. To minimize confusion with all these
new types of controls, naming conventions are a must.
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chk Check box
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cbo Combo box
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cmd Command
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cmg Com. group
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cnt Container
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ctl Control
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(cus Custom)
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edt Edit box
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frm Form
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frs Form set
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grd Grid
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grc Grid column
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grh Grid header
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img Image
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lbl Label
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lin Line
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lst List box
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olb OLE-bound
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ole OLE
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opt Option button
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opg Option group
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(otl Outline)
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pag Page
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pgf Page Frame
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sep Separator
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shp Shape
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spn Spinner
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txt Text box
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tmr Timer
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tbr Toolbar
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Ease your work with Builders
You should really ease your work with the new Builders. We have gone
the hard way today doing everything manual - but with the builders you
are ten times faster for everydays work. There are builders for these
controls:
- Text box
- Edit box
- List box
- Combo-Box
- Option Group
- Command Group
- Grid
By the way, Builders use these special design methods every control has
build in:
- ReadMethod
- WriteMethod
- ReadExpression
- WriteExpression
And the function „ASelObj( )“ will help you to find the selected objects
in case you build a builder on your own. Take a look at a builder-session
to find out more about these predecessors of GenScrnX. You will love
them!
Where to go from here?
There is a lot more to learn about Visual FoxPro and ist new user interface.
Try one of the following sessions here on FoxTeach:
- The Form Designer - Alan Schwartz
- Advanced Visual FoxPro Controls - Ted Roche
- Using the Grid Control in the Real World - Whil Hentzen
- OLE Custom Controls in Visual FoxPro - Steven Black
- Builders in Visual FoxPro - Steven Black
- Using Visual FoxPro Classes - Ken Levy
- The Class Browser - Ken Levy
I know all of these speakers and really recommend their sessions to you.
About the speaker:
Rainer Becker has been programming with Foxpro for several years. He
is the founder of the German FoxPro User Group dFPUG, a semi-professional
group of 1100+ programmers in Germany, Austria and Switzerland. The dFPUG
publishes a bimonthly 32-pages newsletter with companion disk, it organizes
120 small meetings, 50 workshops and a FoxPro developers conference a
year and provides an own section in CompuServe. His main profession is
programming complete software packages for public school administrations,
corporate controlling departments and publishing companies. You can reach
him via Fax (01149-6173-65997), Phone (01149-6173-68182) and CompuServe
(CIS-ID 100024,1364) or by placing a message in the dFPUG-section (GO
MSCESYS).
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