Author: Tomas Rutkauskas
Is it possible to add controls to a form at runtime, then stream the result to
single file, thus preserving all changes for next application run?
Answer:
Yes, with some caveats. You need to register all control classes that are used on
the form plus all that the user may add at runtime. Here is a little example:
1 unit Unit1;
2
3 interface
4
5 uses
6 Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
7 StdCtrls;
8
9 type
10 TForm1 = class(TForm)
11 Button1: TButton;
12 Button2: TButton;
13 procedure Button1Click(Sender: TObject);
14 procedure Button2Click(Sender: TObject);
15 procedure FormCreate(Sender: TObject);
16 private
17 { Private declarations }
18 public
19 { Public declarations }
20 end;
21
22 var
23 Form1: TForm1;
24
25 implementation
26
27 {$R *.DFM}
28
29 const
30 formdata = 'formdata.bin';
31
32 procedure TForm1.Button1Click(Sender: TObject);
33 begin
34 with TEdit.Create(self) do
35 begin
36 left := button1.Left + button1.width + 10;
37 top := button1.top;
38 Name := 'NewEdit';
39 parent := self;
40 end;
41 end;
42
43 procedure TForm1.Button2Click(Sender: TObject);
44 var
45 fs: TFileStream;
46 begin
47 fs := TFileStream.Create(ExtractFilePath(ParamStr(0)) + formdata, fmCreate);
48 try
49 fs.WriteComponent(self);
50 finally
51 fs.free
52 end;
53 end;
54
55 procedure TForm1.FormCreate(Sender: TObject);
56 var
57 filename: string;
58 fs: TFileStream;
59 i: integer;
60 begin
61 filename := ExtractFilePath(ParamStr(0)) + formdata;
62 if fileExists(filename) then
63 begin
64 for i := ComponentCount - 1 downto 0 do
65 Components[i].Free;
66 fs := Tfilestream.create(filename, fmOpenRead or fmShareDenyWrite);
67 try
68 fs.ReadComponent(self);
69 button1.enabled := false;
70 finally
71 fs.free
72 end;
73 end;
74 end;
75
76 initialization
77 RegisterClasses([TButton, TEdit]);
78 end.
|
