为 TCustomControl Delphi 捕获/创建 OnGetFocus/OnLostFocus 事件

Posted 2023-02-23

【中文标题】为 TCustomControl Delphi 捕获/创建 OnGetFocus/OnLostFocus 事件

【英文标题】：catch/create OnGetFocus/OnLostFocus events for TCustomControl Delphi

【发布时间】：2015-09-15 02:59:09

【问题描述】：

我创建了一个继承自 TCustomControl 的 Delphi 组件。该组件可以从 TWinControl 继承来获得焦点，但是当它获得焦点时我需要“突出显示”并在它失去焦点时更改一些属性。 正如 Delphi 文档所说，TCustomControl 没有继承的 OnFocus 事件，所以我需要捕获事件（？）并实现我自己的 OnGetFocus/OnLostFocus 事件处理程序（？）。 当组件获得/失去焦点时如何捕获事件？

【问题讨论】：

覆盖 DoEnter 和 DoExit 方法。

非常感谢@TLama，这正是我要找的东西

@TLama：这应该作为答案发布，而不是评论。

【参考方案1】：

当控件接收或失去输入焦点时触发的事件是OnEnter 和OnExit，它们是从您作为组件开发人员应该重写的DoEnter 和DoExit 方法触发的：

type
  TMyControl = class(TCustomControl)
  protected
    procedure DoEnter; override;
    procedure DoExit; override;
  end;

implementation

 TMyControl 

procedure TMyControl.DoEnter;
begin
  inherited;
  // the control received the input focus, so do what you need here; note
  // that it's recommended to call inherited inside this method (which as
  // described in the reference should only fire the OnEnter event now)
end;

procedure TMyControl.DoExit;
begin
  inherited;
  // the control has lost the input focus, so do what you need here; note
  // that it's recommended to call inherited inside this method (which as
  // described in the reference should only fire the OnExit event now)
end;