Navigation: ABC Library Reference > IncrementalLocatorClass >====== IncrementalLocatorClass Overview ====== | |
The IncrementalLocatorClass is an EntryLocatorClass that activates on each additional search character added to the search value (not when the locator control is accepted).
Use an Incremental locator when you want a multi-character search on numeric or alphanumeric keys and you want the search to take place immediately upon the end user's keystroke.
IncrementalLocatorClass Concepts
An IncrementalLocator is a multi-character locator, with no locator control required (but strongly recommended).
The locator control may be a STRING, ENTRY, COMBO, or SPIN, however, any control other than a STRING causes the Incremental locator to behave like an Entry locator–the search is delayed until the control is accepted.
With a STRING control (or no control), when the BrowseClass LIST has focus, keyboard input characters are automatically added to the locator's search value string for each keystroke, and the BrowseClass immediately advances to the nearest matching record. The Backspace key removes characters from the locator's search value string.
We strongly recommend using a STRING control as the Incremental Locator control for the following reasons:
So the search occurs immediately with each keystoke, and
So the user can see the value for which the BrowseClass object is searching.
IncrementalLocatorClass Relationship to Other Application Builder Classes
The BrowseClass uses the IncrementalLocatorClass to locate and scroll to the nearest matching item. Therefore, if your program's BrowseClass objects use an Incremental Locator, your program must instantiate the IncrementalLocatorClass for each use. Once you register the IncrementalLocatorClass object with the BrowseClass object (see BrowseClass.AddLocator), the BrowseClass object uses the IncrementalLocatorClass object as needed, with no other code required. See the Conceptual Example.
IncrementalLocatorClass ABC Template Implementation
The ABC BrowseBox template generates code to instantiate the IncrementalLocatorClass for your BrowseBoxes. The IncrementalLocatorClass objects are called BRWn::Sort#:Locator, where n is the template instance number and # is the sort sequence (id) number. As this implies, you can have a different locator for each BrowseClass object sort order.
You can use the BrowseBox's Locator Behavior dialog (the Locator Class button) to derive from the EntryLocatorClass. The templates provide the derived class so you can modify the locator's behavior on an instance-by-instance basis.
IncrementalLocatorClass Source Files
The IncrementalLocatorClass source code is installed by default to the Clarion \LIBSRC folder. The IncrementalLocatorClass source code and its respective components are contained in:
ABBROWSE.INC | IncrementalLocatorClass declarations | |
ABBROWSE.CLW | IncrementalLocatorClass method definitions |
IncrementalLocatorClass Conceptual Example
The following example shows a typical sequence of statements to declare, instantiate, initialize, use, and terminate a BrowseClass object and related objects, including a IncrementalLocatorClass object. The example initializes and page-loads a LIST, then handles a number of associated events, including scrolling, updating, and locating records.
Note that the WindowManager and BrowseClass objects internally handle the normal events surrounding the locator.
PROGRAM
INCLUDE('ABWINDOW.INC') !declare WindowManager class
INCLUDE('ABBROWSE.INC') !declare BrowseClass and Locator
MAP
END
State FILE,DRIVER('TOPSPEED'),PRE(ST),THREAD
StateCodeKey KEY(ST:STATECODE),NOCASE,OPT
Record RECORD,PRE()
STATECODE STRING(2)
STATENAME STRING(20)
END
END
StView VIEW(State) !declare VIEW to process
END
StateQ QUEUE !declare Q for LIST
ST:STATECODE LIKE(ST:STATECODE)
ST:STATENAME LIKE(ST:STATENAME)
ViewPosition STRING(512)
END
Access:State CLASS(FileManager) !declare Access:State object
Init PROCEDURE
END
Relate:State CLASS(RelationManager) !declare Relate:State object
Init PROCEDURE
END
VCRRequest LONG(0),THREAD
StWindow WINDOW('Browse States'),AT(,,123,152),IMM,SYSTEM,GRAY
PROMPT('Find:'),AT(9,6)
STRING(@s2),AT(29,4),USE(ST:STATECODE) !locator control
LIST,AT(8,5,108,124),USE(?StList),IMM,HVSCROLL,FROM(StateQ),|
FORMAT('27L(2)|M~CODE~@s2@80L(2)|M~STATENAME~@s20@')
END
ThisWindow CLASS(WindowManager) !declare ThisWindow object
Init PROCEDURE(),BYTE,PROC,VIRTUAL
Kill PROCEDURE(),BYTE,PROC,VIRTUAL
END
BrowseSt CLASS(BrowseClass) !declare BrowseSt object
Q &StateQ
END
StLocator IncrementalLocatorClass !declare StLocator object
StStep StepStringClass !declare StStep object
CODE
ThisWindow.Run() !run the window procedure
ThisWindow.Init PROCEDURE() !initialize things
ReturnValue BYTE,AUTO
CODE
ReturnValue = PARENT.Init() !call base class init
IF ReturnValue THEN RETURN ReturnValue.
Relate:State.Init !initialize Relate:State object
SELF.FirstField = ?StList !set FirstField for ThisWindow
SELF.VCRRequest &= VCRRequest !VCRRequest not used
Relate:State.Open !open State and related files
!Init BrowseSt object by naming its LIST,VIEW,Q,RelationManager & WindowManager
BrowseSt.Init(?StList,StateQ.ViewPosition,StView,StateQ,Relate:State,SELF)
OPEN(StWindow)
SELF.Opened=True
BrowseSt.Q &= StateQ !reference the browse QUEUE
StStep.Init(+ScrollSort:AllowAlpha,ScrollBy:Runtime)!initialize the StStep object
BrowseSt.AddSortOrder(StStep,ST:StateCodeKey)!set the browse sort order
BrowseSt.AddLocator(StLocator) !plug in the browse locator
StLocator.Init(?ST:STATECODE,ST:STATECODE,1,BrowseSt)!initialize the locator object
BrowseSt.AddField(ST:STATECODE,BrowseSt.Q.ST:STATECODE) !set a column to browse
BrowseSt.AddField(ST:STATENAME,BrowseSt.Q.ST:STATENAME) !set a column to browse
SELF.SetAlerts() !alert any keys for ThisWindow
RETURN ReturnValue
ThisWindow.Kill PROCEDURE() !shut down things
ReturnValue BYTE,AUTO
CODE
ReturnValue = PARENT.Kill() !call base class shut down
IF ReturnValue THEN RETURN ReturnValue.
Relate:State.Close !close State and related files
Relate:State.Kill !shut down Relate:State object
GlobalErrors.Kill !shut down GlobalErrors object
RETURN ReturnValue