Delphi XE2 之 FireMonkey 入门(28) 数据绑定: TBindingsList: 表达式函数测试: SelectedText()、CheckedState()

示例构想: 用 Label1 显示 ListBox1 的选项, 用 Label2 显示 CheckBox1 的状态.

1、放控件: Label1、Label2、ListBox1、CheckBox1、BindingsList1、BindScope1;
2、激活 ListBox1 的 OnClick 事件和窗体的默认事件.

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unit Unit1;

interface

uses
  System.SysUtils, System.Types, System.UITypes, System.Classes, System.Variants,
  FMX.Types, FMX.Controls, FMX.Forms, FMX.Dialogs, Data.Bind.EngExt,
  Fmx.Bind.DBEngExt, Data.Bind.Components, FMX.Layouts, FMX.ListBox;

type
  TForm1 = class(TForm)
    Label1: TLabel;
    Label2: TLabel;
    ListBox1: TListBox;
    CheckBox1: TCheckBox;
    BindingsList1: TBindingsList;
    BindScope1: TBindScope;
    procedure FormCreate(Sender: TObject);
    procedure ListBox1Click(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.fmx}

uses Fmx.Bind.Editors; //使用表达式函数 SelectedText、SelectedItem、CheckedState 时, 需要的支持单元

procedure TForm1.FormCreate(Sender: TObject);
var
  i: Integer;
begin
  for i := 1 to 9 do
    ListBox1.Items.Add('Item_' + IntToStr(i));

  with TBindExpression.Create(BindingsList1) do
  begin
    ControlComponent := Label1;
    ControlExpression := 'Text';
    SourceComponent := BindScope1;
    SourceExpression := 'SelectedText(ListBox1)';   //同下一行
//    SourceExpression := 'ListBox1.Selected.Text';
    Active := True;
  end;

  with TBindExpression.Create(BindingsList1) do
  begin
    ControlComponent := Label2;
    ControlExpression := 'Text';
    SourceComponent := BindScope1;
    SourceExpression := 'CheckedState(CheckBox1)'; //Checked: 'True'; Unchecked: 'False'; Grayed: ''
//    SourceExpression := 'CheckBox1.IsChecked';   //在本例中, 这等同于上一行
    Active := True;
  end;

  CheckBox1.OnClick := ListBox1.OnClick;
end;

procedure TForm1.ListBox1Click(Sender: TObject);
begin
  BindingsList1.Notify(Sender, '');
end;

end.

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