在我的主要表单中，我有一个按钮，可以打开一个模态Form2（可以打开其他模态表单）。在打开Form2之前我正在设置一个计时器，它将以编程方式关闭所有活动的模态表单（Form2.Close）并打开一个新的模态Form3。
问题是当Form3以模态方式打开时，Form2保持（可见），并且仅当我通过点击Form3将X关闭Form2时关闭TButton
要重现向项目添加3个表单，请添加TTimer，并在Form1（主表单）上删除unit Unit1;
interface
uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
StdCtrls, ExtCtrls;
type
TForm1 = class(TForm)
Button1: TButton;
Timer1: TTimer;
procedure Button1Click(Sender: TObject);
procedure FormCreate(Sender: TObject);
procedure Timer1Timer(Sender: TObject);
private
public
end;
var
Form1: TForm1;
implementation
uses Unit2, Unit3;
{$R *.DFM}
procedure TForm1.FormCreate(Sender: TObject);
begin
Timer1.Enabled := False;
end;
procedure TForm1.Button1Click(Sender: TObject);
begin
Timer1.Enabled := True;
with TForm2.Create(Application) do
try
ShowModal;
finally
Free;
end;
end;
procedure CloseActiveModalForms;
var
I: Integer;
F: TCustomForm;
L: TList; // list of modal forms
begin
L := TList.Create;
try
for I := 0 to Screen.CustomFormCount - 1 do
begin
F := Screen.CustomForms[I];
if (fsModal in F.FormState) then
L.Add(F);
end;
for I := 0 to L.Count - 1 do
TCustomForm(L.Items[I]).Close; // this sets ModalResult := mrCancel
finally
L.Free;
end;
end;
procedure TForm1.Timer1Timer(Sender: TObject);
begin
Timer1.Enabled := False;
CloseActiveModalForms; // this should close TForm2 but it does not.
with TForm3.Create(Application) do // create new Modal TForm3
try
ShowModal;
finally
Free;
end;
end;
end.
：
Form2为什么Form2没有关闭？调用CloseActiveModalForms后，为什么D: $dcmtk: dsrdump v3.6.1 DEV $
D:
[...]
W: Date (0040,a121) empty in content item (type 1)
W: Reading invalid/incomplete content item DATE "1.3.1"
E: Reading content item DATE "1.3.1" (Invalid Value)
D: ------------------------------- DICOM DATA SET -------------------------------
D: (fffe,e000) na (Item with explicit length #=4) # 98, 1 Item
D: (0040,a010) CS [CONTAINS] # 8, 1 RelationshipType
D: (0040,a040) CS [DATE] # 4, 1 ValueType
D: (0040,a043) SQ (Sequence with explicit length #=1) # 54, 1 ConceptNameCodeSequence
D: (fffe,e000) na (Item with explicit length #=3) # 46, 1 Item
D: (0008,0100) SH [11779-6] # 8, 1 CodeValue
D: (0008,0102) SH [LN] # 2, 1 CodingSchemeDesignator
D: (0008,0104) LO [EDD from LMP] # 12, 1 CodeMeaning
D: (fffe,e00d) na (ItemDelimitationItem for re-encoding) # 0, 0 ItemDelimitationItem
D: (fffe,e0dd) na (SequenceDelimitationItem for re-encod.) # 0, 0 SequenceDelimitationItem
D: (0040,a121) DA (no value available) # 0, 0 Date
D: (fffe,e00d) na (ItemDelimitationItem for re-encoding) # 0, 0 ItemDelimitationItem
D: ------------------------------------------------------------------------------
E: Reading content item CONTAINER "1.3" (Invalid Value)
模态循环没有退出？
答案 0 :(得分：5)
您的调用堆栈如下所示：
1 Form1.Button1Click
2 Form2.ShowModal //Local message processing loop until form closes
3 Form1.Timer1Timer //Here you attempt to close the form
//but it doesn't actually until ShowModal exits
4 Form3.ShowModal // Another message loop that doesn't return until form closes
基本上，在Form3关闭之前，你无法完成Form2的关闭。请注意，ShowModal是阻止调用以显示表单。如果您只是Show Form3（即不是ShowModal），则调用不会阻止，并且您将看到Form2能够在调用堆栈展开时关闭。
你应该可以通过延迟调用show Form3直到Form2关闭之后来解决这个问题。 OnFormDestroyEvent应该足够了（遗憾的是我无法测试它）。
procedure TForm1.ShowForm3(Sender: TObject);
var
LForm: TForm;
begin
LForm := TForm3.Create(Application); //as you created it, but nil owner should suffice
try
LForm.ShowModal;
finally
LForm.Free;
end;
end;
procedure TForm1.Timer1Timer(Sender: TObject);
begin
Timer1.Enabled := False;
//You will need to figure out how you reference the Form2 instance.
Form2.OnFormDestroy := ShowForm3;
CloseActiveModalForms;
//Form2 will close after you backtrack up the call-stack.
//When it's destroyed, your event handler will create and show a TForm3 instance.
end;
注意上面简单地说明了这个概念。根据您的最终目标，您需要设计一种更强大的方法。
但是，我建议过度使用模态表格通常被认为在用户体验方面不友好。