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>> LCL Components >> TListBox

This page explains how to use the TListBox component. When I mention to click on something, unless I explicitly say to right-click, you always left-click on the item in question.


A scrollable list of strings.

Comp Standard TListBox.png


To use a TListBox on a form, you can simply select it on the Standard component pallet and place it by clicking on the form.

In the ListBox, the stored strings are stored in the property Items, that is of type TStrings. Thus you can assign or remove strings in the ListBox, as in a TStringList or its parent TStrings.

Here are a few examples of how to use a ListBox ListBox1 on a form Form1:

Fill ListBox

by the Object Inspector

  • Select the ListBox on your form with one click.
  • Go in the Object Inspector in the Properties tab on the property Items.
  • Click on the button with the three dots. The String Editor opens.
  • Enter your text and confirm your work with OK.

by code in button click

Add your form a TButton with the name btnFill and caption fill ListBox. In the event handler OnClick of the button, you write the following code:

procedure TForm1.btnFillClick(Sender: TObject);
  ListBox1.Items.Clear;             //Delete all existing strings
  ListBox1.Items.Add('First line');
  ListBox1.Items.Add('Line with random number '+IntToStr(Random(100)));
  ListBox1.Items.Add('Third line');
  ListBox1.Items.Add('Even a random number '+IntToStr(Random(100)));

Assignment of a StringList

Add your form a TButton with the name btnFill and caption fill ListBox. In the event handler OnClick of the button, you write the following code:

procedure TForm1.btnFillClick(Sender: TObject);
  myStringList: TStringList;
  myStringList:=TStringList.Create;               //Create my StringList
  myStringList.Add('This is the first line.');   //This add a row
  myStringList.Add('This is the second first line.');
  myStringList.Add('This is the third line.');
  ListBox1.Items.Assign(myStringList);            //assign the ListBox1 the text content of my StringList
  myStringList.Free;                              //Free my StringList in memory 

Add string

  • Extend the example Fill ListBox by code in button click to a TEdit and a TButton with the name btnAdd and caption add string. Change of Edit1 the property Text to "" - empty string.
  • In the event handler OnClick of the button, you write the following code:
procedure TForm1.btnAddClick(Sender: TObject);

Delete string

By default is set that you can select only one row in your list box. Do you want to select several of the lines in your ListBox, you would have the property MultiSelect to make True.

Delete string at ItemIndex

  • Extend the example Add string to a TButton with the name "btnDel" and caption "delete string".
  • In the event handler OnClick of the button, you write the following code:
procedure TForm1.btnDelClick(Sender: TObject);
  if ListBox1.ItemIndex > -1 then    //Delete only when a string in the listbox is selected

Delete all selected strings

  • Extend the example Add string to a TButton with the name "btnDel" and caption "delete string".
  • In the event handler OnClick of the button, you write the following code:
procedure TForm1.btnDelClick(Sender: TObject);
  i: Integer;
  if ListBox1.SelCount > 0 then                 //Delete only if at least one string in the list box is selected
    for i:=ListBox1.Items.Count - 1 downto 0 do //Iterate through all the items
      if ListBox1.Selected[i] then              //If selected...
        ListBox1.Items.Delete(i);               //...delete the item (String)

Owner-drawn ListBox

In general, it is advantageous to let the ListBox represent in theme by the setting of the user. In some cases (for example, to program a game with a colorful surface), you can deviate from this standard and draw the according to your own choice. You can try this now:

  • You can modify the previous sample or create a new application with a TListBox ListBox1.
  • In the Object Inspector, change ListBox1 property Style to lbOwnerDrawFixed.
  • With the Object Inspector, tab events, create the event handler for the event OnDrawItem, by clicking on the button [...].
  • You add the following code to the handler:
procedure TForm1.ListBox1DrawItem(Control: TWinControl; Index: Integer;
  ARect: TRect; State: TOwnerDrawState);
  aColor: TColor;                       //Background color
  if (Index mod 2 = 0)                  //Index tells which item it is
    then aColor:=$FFFFFF                //every second item gets white as the background color
    else aColor:=$EEEEFF;               //every second item gets pink background color
  if odSelected in State then aColor:=$0000FF;  //If item is selected, then red as background color
  ListBox1.Canvas.Brush.Color:=aColor;  //Set background color
  ListBox1.Canvas.FillRect(ARect);      //Draw a filled rectangle

  ListBox1.Canvas.Font.Bold:=True;      //Set the font to "bold"
  ListBox1.Canvas.TextRect(ARect, 2, ARect.Top+2, ListBox1.Items[Index]);  //Draw Itemtext

Note: Parameters of ListBoxDrawItem:

If multiple controls (E.g. multiple ListBoxes) access this event handle, you know which threw this event. You could in our example, instead of ListBox1.Canvas.FillRect(ARect) also TListBox(Control).Canvas.FillRect(ARect) write, where you should query still possible before, whether it is a TListBox:

  if Control is TListBox then

Index: Specifies the item location, so you have access to the string <ListBox>.Items[Index].
ARect: Describes the rectangle, which is necessary for drawing the background.
State: Status of the items, whether normal, focused, selected etc.

  • Your example could look like:

ListBoxBsp1.png -> ListBoxBsp2.png

See also

TMemo - Control for editable multi-line text

Return To: LCL Components  — Previous: TRadioButton Next: TComboBox

LCL Components
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Standard TMainMenu • TPopupMenu • TButton • TLabel • TEdit • TMemo • TToggleBox • TCheckBox • TRadioButton • TListBox • TComboBox • TScrollBar • TGroupBox • TRadioGroup • TCheckGroup • TPanel • TFrame • TActionList
Additional TBitBtn • TSpeedButton • TStaticText • TImage • TShape • TBevel • TPaintBox • TNotebook • TLabeledEdit • TSplitter • TTrayIcon • TControlBar • TFlowPanel • TMaskEdit • TCheckListBox • TScrollBox • TApplicationProperties • TStringGrid • TDrawGrid • TPairSplitter • TColorBox • TColorListBox • TValueListEditor
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Data Controls TDBNavigator • TDBText • TDBEdit • TDBMemo • TDBImage • TDBListBox • TDBLookupListBox • TDBComboBox • TDBLookupComboBox • TDBCheckBox • TDBRadioGroup • TDBCalendar • TDBGroupBox • TDBGrid • TDBDateTimePicker
Data Access TDataSource • TCSVDataSet • TSdfDataSet • TBufDataset • TFixedFormatDataSet • TDbf • TMemDataset
System TTimer • TIdleTimer • TLazComponentQueue • THTMLHelpDatabase • THTMLBrowserHelpViewer • TAsyncProcess • TProcessUTF8 • TProcess • TSimpleIPCClient • TSimpleIPCServer • TXMLConfig • TEventLog • TServiceManager • TCHMHelpDatabase • TLHelpConnector
Misc TColorButton • TSpinEdit • TFloatSpinEdit • TArrow • TCalendar • TEditButton • TFileNameEdit • TDirectoryEdit • TDateEdit • TTimeEdit • TCalcEdit • TFileListBox • TFilterComboBox • TComboBoxEx • TCheckComboBox • TButtonPanel • TShellTreeView • TShellListView • TXMLPropStorage • TINIPropStorage • TJSONPropStorage • TIDEDialogLayoutStorage • TMRUManager • TStrHolder
LazControls TCheckBoxThemed • TDividerBevel • TExtendedNotebook • TListFilterEdit • TListViewFilterEdit • TLvlGraphControl • TShortPathEdit • TSpinEditEx • TFloatSpinEditEx • TTreeFilterEdit • TExtendedTabControl •
RTTI TTIEdit • TTIComboBox • TTIButton • TTICheckBox • TTILabel • TTIGroupBox • TTIRadioGroup • TTICheckGroup • TTICheckListBox • TTIListBox • TTIMemo • TTICalendar • TTIImage • TTIFloatSpinEdit • TTISpinEdit • TTITrackBar • TTIProgressBar • TTIMaskEdit • TTIColorButton • TMultiPropertyLink • TTIPropertyGrid • TTIGrid
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Pascal Script TPSScript • TPSScriptDebugger • TPSDllPlugin • TPSImport_Classes • TPSImport_DateUtils • TPSImport_ComObj • TPSImport_DB • TPSImport_Forms • TPSImport_Controls • TPSImport_StdCtrls • TPSCustomPlugin
SynEdit TSynEdit • TSynCompletion • TSynAutoComplete • TSynMacroRecorder • TSynExporterHTML • TSynPluginSyncroEdit • TSynPasSyn • TSynFreePascalSyn • TSynCppSyn • TSynJavaSyn • TSynPerlSyn • TSynHTMLSyn • TSynXMLSyn • TSynLFMSyn • TSynDiffSyn • TSynUNIXShellScriptSyn • TSynCssSyn • TSynPHPSyn • TSynTeXSyn • TSynSQLSyn • TSynPythonSyn • TSynVBSyn • TSynAnySyn • TSynMultiSyn • TSynBatSyn • TSynIniSyn • TSynPoSyn
Chart TChart • TListChartSource • TRandomChartSource • TUserDefinedChartSource • TCalculatedChartSource • TDbChartSource • TChartToolset • TChartAxisTransformations • TChartStyles • TChartLegendPanel • TChartNavScrollBar • TChartNavPanel • TIntervalChartSource • TDateTimeIntervalChartSource • TChartListBox • TChartExtentLink • TChartImageList
IPro TIpFileDataProvider • TIpHtmlDataProvider • TIpHttpDataProvider • TIpHtmlPanel
Virtual Controls TVirtualDrawTree • TVirtualStringTree • TVTHeaderPopupMenu

--Michl 22:40, 26 May 2014 (CEST)