如何从代码获取ComboBox的SelectedValue？ [英] How do I get the SelectedValue of a ComboBox from code?

问题描述

我正在尝试使用LiveBindings来构建一个类似于 TLookupComboBox 的东西。

我已经放置了一个普通的 TComboBox 在VCL表单上。我还有一些数据集，其中包含两个字段 id 和 text 。

然后我使用LiveBindings编辑器创建一个 TBindSourceDB 和一个 TBindingsList 。 / p>

只有一个绑定：

 对象BindingsList1：TBindingsList 
方法=<> 
 OutputConverters =<> 
 UseAppManager = True 
 Left = 244 
顶部= 229 
对象LinkFillControlToField1：TLinkFillControlToField 
类别='快速绑定'
 Control = ComboBox1 
 Track = True 
 FillDataSource = BindSourceDB1 
 FillValueFieldName ='id'
 FillDisplayFieldName ='text'
 AutoFill = True 
 BufferCount = -1 
 FillExpressions =< ;> 
 end 
 end 
  

正如你所看到的，我有不同的 FillValueFieldName 和 FillDisplayFieldName 。

LiveBindings设计器如下所示：

ComboBox中填充了文本的值，所以我认为我正确设置。

如何从代码中获取 SelectedValue

我可以直观地绑定值为 TLabel ，然后我可以读取 TLabel.Caption ，但肯定有一个更简单的方法？ / p>

PS：我不想将值存储在数据库中，否则我只需使用 TDBLookupComboBox 。 / p>

编辑：我尝试使用一个 TPrototypeBindSource ，但这没有明显的方法从代码访问字段。我还试图使用第二个 TBindSourceDB 以及一个 TClientDataSet ，但这感觉就像使用大锤破解一个坚果。

解决方案

您可以通过相应的 TLinkFillControlToField ：

  procedure TForm1.ComboBox1Change（Sender：TObject）; 
 var 
 SelectedValue：Integer; 
 begin 
如果TryStrToInt（LinkFillControlToField1.BindList.GetSelectedValue.AsString，SelectedValue）然后
 DoSomethingWith（SelectedValue）; 
结束
  

I am trying to build something like a TLookupComboBox using LiveBindings.

I have placed a normal TComboBox on a VCL form. I also have a data set with some rows that have the two fields id and text.

Then I used the LiveBindings editor to create a TBindSourceDB and a TBindingsList.

There is just one binding in it:

object BindingsList1: TBindingsList
  Methods = <>
  OutputConverters = <>
  UseAppManager = True
  Left = 244
  Top = 229
  object LinkFillControlToField1: TLinkFillControlToField
    Category = 'Quick Bindings'
    Control = ComboBox1
    Track = True
    FillDataSource = BindSourceDB1
    FillValueFieldName = 'id'
    FillDisplayFieldName = 'text'
    AutoFill = True
    BufferCount = -1
    FillExpressions = <>
  end
end

As you can see I have different fields for FillValueFieldName and FillDisplayFieldName.

The LiveBindings designer looks like this:

The ComboBox is filled with the values from the field text, so I think I set it up correctly.

How can I get the SelectedValue from code?

I could visually bind the value to a TLabel and then I could read the TLabel.Caption, but surely there is an easier way?

PS: I do not want to store the value in the DB, otherwise I would just use a TDBLookupComboBox.

Edit: I have tried to use a TPrototypeBindSource, but that has no obvious way to access the fields from code. I have also tried to use a second TBindSourceDB together with a TClientDataSet which works, but that feels like using a sledgehammer to crack a nut.

解决方案

You can access the selected value via the corresponding TLinkFillControlToField:

procedure TForm1.ComboBox1Change(Sender: TObject);
var
    SelectedValue: Integer;
begin
    if TryStrToInt(LinkFillControlToField1.BindList.GetSelectedValue.AsString, SelectedValue) then
      DoSomethingWith(SelectedValue);
end;

这篇关于如何从代码获取ComboBox的SelectedValue？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！