OnChange event occurs when the user changes the text displayed in the edit region.
We write an OnChange event handler to take specific action immediately after the user edits the text in the edit region or selects an item from the list. The Text property gives the new value in the edit region.
Note: OnChange only occurs in response to user actions. Changing the Text property programmatically does not trigger an OnChange event.
Here is the working example of the implementation of an OnChange event:
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# Combobox creation cbxCity = ComboBox(pgOne) cbxCity.SetProps(Parent=pgOne,Name='ComboBox') cbxCity.SetBounds(145,206,121,60) cbxCity.Items.Add('New York') cbxCity.Items.Add('Sydney') cbxCity.Items.Add('Banglore') cbxCity.Items.Add('Tokyo') def ChangeHandler(sender): memoEvent.Lines.Add('changed') cbxCity.OnChange = ChangeHandler |
To see the result, let’s run the complete script:
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from DelphiVCL import * class MainForm(Form): def __init__(self, Owner): self.Caption = "Components Overview Sample" self.Name = "BaseForm" self.SetBounds(10, 10, 700, 650) # pnlMain = CreateComponent('TPanel',Owner) pnlMain.SetProps(Parent=self, Caption="",align = "alClient", Name = "MainPanel") # page control creation pgConMain = PageControl(pnlMain) pgConMain.Name = "MyPageControl" pgConMain.Parent = pnlMain pgConMain.Align = "alClient" # Tabsheet one pgOne = TabSheet(pnlMain) pgOne.PageControl = pgConMain pgOne.Caption = "StandardControls" # label Creation lblHello = CreateComponent('TLabel',pgOne) lblHello.Parent = pgOne lblHello.Caption = 'FirstName' lblHello.Name = 'Name' lblHello.Left = 20 lblHello.Top = 14 lblHello.Width = 121 lblHello.Height = 30 # Edit box creation edtHello = CreateComponent('TEdit',pgOne) edtHello.Parent = pgOne edtHello.Text = 'Jim' edtHello.Name = 'edtFirstName' edtHello.Left = 145 edtHello.Top = 14 edtHello.Width = 121 edtHello.Height = 30 chkSingle = CheckBox(self) chkSingle.Parent = pgOne chkSingle.Caption = 'Single ?' chkSingle.Alignment = 'taLeftJustify' chkSingle.SetBounds(20, 44, 141, 30) # label Creation lblCountry = CreateComponent('TLabel',pgOne) lblCountry.SetProps(Parent=pgOne,Caption='Country') lblCountry.SetBounds(20,88,121,30) #listbox lboxCountry = ListBox(pgOne) lboxCountry.SetProps(Parent=pgOne) lboxCountry.SetBounds(145,88,121,60) lboxCountry.Items.Add('RUSSIA') lboxCountry.Items.Add('USA') lboxCountry.Items.Add('INDIA') lboxCountry.Items.Add('AUSTRALIA') # label Creation lblDateOfIssue = CreateComponent('TLabel',pgOne) lblDateOfIssue.SetProps(Parent=pgOne,Caption='Date Of Birth') lblDateOfIssue.SetBounds(20,162,121,30) dtpDateofIssue = CreateComponent('TDateTimePicker',pgOne) dtpDateofIssue.SetProps(Parent=pgOne) dtpDateofIssue.SetBounds(145,162,121,30) # label Creation lblCity = CreateComponent('TLabel',pgOne) lblCity.SetProps(Parent=pgOne,Caption='City') lblCity.SetBounds(20,206,121,30) #Combobox cbxCity = ComboBox(pgOne) cbxCity.SetProps(Parent=pgOne,Name='ComboBox') cbxCity.SetBounds(145,206,121,60) cbxCity.Items.Add('New York') cbxCity.Items.Add('Sydney') cbxCity.Items.Add('Banglore') cbxCity.Items.Add('Tokyo') def ChangeHandler(sender): memoEvent.Lines.Add('changed') cbxCity.OnChange = ChangeHandler # Radiogroup Creation rbgRadioBox = RadioGroup(pgOne) rbgRadioBox.SetProps(Parent=pgOne,Caption='Gender') rbgRadioBox.SetBounds(20,250,242,90) rbgRadioBox.Items.Add('Male') rbgRadioBox.Items.Add('Female') #Button btnOK = Button(pgOne) btnOK.SetProps(Parent=pgOne,Caption = 'Submit',Name = 'btnOK') btnOK.SetBounds(145,540,60,30) #Memo memoEvent = Memo(pgOne) memoEvent.SetProps(Parent=pgOne) memoEvent.SetBounds(300,14,350,300) def ClickHandler(Sender): memoEvent.Lines.Add(Sender.Name + ' clicked') btnOK.OnClick = ClickHandler # Tabsheet two pgTwo = TabSheet(pnlMain) pgTwo.PageControl = pgConMain pgTwo.Caption = "Ext controls" shpRectangle = Shape(pgTwo) shpRectangle.SetProps(Parent=pgTwo,Shape = 'stRectangle') shpRectangle.SetBounds(140,14,400,200) clbSelect = ColorBox(pgTwo) clbSelect.SetProps(Parent=pgTwo) clbSelect.SetBounds(20,14,100,30) def ColorChangeHandler(Sender): shpRectangle.Brush.Color = clbSelect.Selected clbSelect.Onchange = ColorChangeHandler grdTest = DrawGrid(pgTwo) grdTest.Parent = pgTwo grdTest.SetBounds(20, 220, 520, 180) def grdTestDrawCell(Sender, Col, Row, Rect, State): if gdSelected in State: Sender.Canvas.Brush.Color = clBlue # 0x00ff0000 # blue Sender.Canvas.TextRect(Rect, Rect.Left+2, Rect.Top+2, "%d @ %d" % (Col, Row)) def grdTestSelectCell(Sender, Col, Row, CanSelect): if Col == 2 and Row == 2: CanSelect.Value = False grdTest.OnDrawCell = grdTestDrawCell grdTest.OnSelectCell = grdTestSelectCell self.OnClose = self.MainFormClose def MainFormClose(self, Sender, Action): Action.Value = caFree def btnOKClick(self, Sender): btnOK.Caption = "Clicked" def main(): Application.Initialize() Application.Title = "MyDelphiApp" f = MainForm(Application) f.Show() FreeConsole() Application.Run() main() |
Check out DelphiVCL which easily allows you to build GUIs for Windows using Python.
