Delphi 进入TEdit控件时选中该控件中的内容，不使用SelectAll　

T(Custom)Edit's AutoSelect
property determines whether all the text in the edit control is automatically selected when the control gets focus.

The AutoSelect property has the value of TRUE by default - when the control receives the focus, i.e. when the control is tabbed into
all the text in the control will be selected.

And here's a problem! The AutoSelect will auto select the text in
an edit control only when the control receives the focus as a result of
TAB key.

AutoSelect On Click Focus

What I need is that all the text is selected even when the edit control receives the focus from a mouse click.

There's the OnEnter
event which gets fired when the control receives the focus. There's a SelectAll
method which selects all text in the edit control. When you click into a
non-focused edit control, it will receive the focus and the OnEnter
event will get fired.

If you put "Edit.SelectAll" in the OnEnter event, presuming that
the text will be selected when the control receives the focus - you are
wrong :(

The default behavior for the OnClick event sets the caret to the clicked position, clearing any selection if there was one.

The OnClick is called after the OnEnter, this is why calling
SelectAll in OnEnter will not work - the "hidden" OnClick behavior will
clear the selection.

Also, you cannot simply place the call to SelectAll in the
OnClick event handler as every time the user clicks into the edit
control that already has the input focus - all the text will be
selected.

SelectAll On First OnClick Focus

What we want is that AutoSelect works not only when the control is
tabbed into BUT also when the edit control receives the input focus as a
result of a mouse click into the control.

.

And finally, here's a simple trick to make this happen:

//Edit1 OnClick

procedure
TEntryForm.Edit1Click(Sender: TObject);

begin

Edit1.SelectAll;

Edit1.OnClick := nil
;

end
;

//Edit1 OnExit (lost focus)

procedure
TEntryForm.Edit1Exit(Sender: TObject);

begin

Edit1.OnClick := Edit1Click;

end
;

When the OnClick event is fired, the event handler select all the text, then detaches the event handling procedure
(Edit1Click) from the event handler.

This ensures the auto selection will not happen as a result of mouse clicks inside the edit WHILE the edit has the input focus.

To restore the OnClick event handler, set it back again in the
OnExit event - when the input focus shifts away from the edit control to
another.

Of course, you basically loose the OnClick functionality while the edit has the focus ... but you can live without that ;)