Delphi-更改TComboBox的OnChange [英] Delphi - Changing TComboBox's OnChange

问题描述

我想更改 TComboBox ，以便如果我在其中键入文本或手动设置Text属性，它将触发 OnChange 事件。

现在，执行 ComboBox.Text：='blah'不会'不会触发 OnChange 事件，也不会在框中键入内容。

我尝试创建 TComboBox 后代，我认为这是正确的方法，但是我不确定如何更改触发事件的方式。

据我所知，在组合框中键入内容将导致 OnChange 事件触发。

我将如何启动 OnChange 的方式您的组合框将处理 CM_TEXTCHANGED 消息。为此，处理程序需要调用 Change 方法，如果已分配<< c $ c> OnChange ，则该方法将调用 OnChange 。

作为一个简单的示例，这是一个插入器类实现：

  type 
 TComboBox = class（StdCtrls.TComboBox）
受保护的
过程CMTextChanged（var Message：TMessage）;消息CM_TEXTCHANGED; 
结尾； 
 
过程TComboBox.CMTextChanged（var Message：TMessage）; 
开始
继承； 
零钱； 
结尾； 
  

I want to change the TComboBox so that if I type text into it or manually set the Text property it will trigger the OnChange event.

As it is now, doing ComboBox.Text := 'blah' doesn't trigger the OnChange event, nor does typing into the box.

I tried creating a TComboBox descendant, which I assume is the right approach, but I'm not really sure how to change what triggers the events.

解决方案

To the best of my knowledge, typing into a combo box will result in the OnChange event firing. But it is true that modifying the text property does not.

The way I would go about getting OnChange to fire for your combo box is to handle the CM_TEXTCHANGED message. The handler for this needs to call the Change method which will then call OnChange, if it has been assigned.

As a simple example, here's an interposer class implementation:

type
  TComboBox = class(StdCtrls.TComboBox)
  protected
    procedure CMTextChanged(var Message: TMessage); message CM_TEXTCHANGED;
  end;

procedure TComboBox.CMTextChanged(var Message: TMessage);
begin
  inherited;
  Change;
end;

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