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How to write a component resource to a file Turn on/off line numbers in source code. Switch to Orginial background IDE or DSP color Comment or reply to this aritlce/tip for discussion. Bookmark this article to my favorite article(s). Print this article
20-Oct-02
Category
Files Operation
Language
Delphi 2.x
Views
78
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Publisher:
DSP, Administrator
Reference URL:
DKB
			Author: Jonas Bilinkevicius

I decided to change the way my application saves its form details by using 
WriteComponentResFile. Basically, my application allows users to create their own 
forms at run-time (but really just let them change the contents of a panel). Using 
WriteComponentResFile('Panel.Dfm', MainPanel); doesn't write the buttons or images 
held by the panel to the DFM file. All that is saved is the panel info itself.

Answer:

The key is to make the controls the user drops on the panel owned by the panel, not 
the form. Here is an example project to show the principle. Note that you need to 
register all classes the user can drop so the streaming system knowns how to create 
them.

1   unit Unit1;
2   
3   interface
4   
5   uses
6     Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
7     StdCtrls, Menus, ExtCtrls;
8   
9   type
10    TForm1 = class(TForm)
11      CloseButton: TButton;
12      Panel1: TPanel;
13      PopupMenu1: TPopupMenu;
14      Button2: TMenuItem;
15      Edit1: TMenuItem;
16      Label2: TMenuItem;
17      SaveButton: TButton;
18      RestoreButton: TButton;
19      procedure CloseButtonClick(Sender: TObject);
20      procedure PopupMenuClick(Sender: TObject);
21      procedure Panel1MouseDown(Sender: TObject; Button: TMouseButton;
22        Shift: TShiftState; X, Y: Integer);
23      procedure SaveButtonClick(Sender: TObject);
24      procedure RestoreButtonClick(Sender: TObject);
25    private
26      { Private declarations }
27      FPopupPosition: TPoint;
28      function Filename: string;
29      procedure CustomButtonClick(Sender: TObject);
30    public
31      { Public declarations }
32    end;
33  
34  var
35    Form1: TForm1;
36  
37  implementation
38  
39  {$R *.DFM}
40  
41  procedure TForm1.CloseButtonClick(Sender: TObject);
42  begin
43    Close;
44  end;
45  
46  procedure TForm1.PopupMenuClick(Sender: TObject);
47  var
48    ctrl: TControl;
49    S: string;
50    i: Integer;
51  begin
52    case (Sender as TMenuItem).Tag of
53      1:
54        begin
55          ctrl := TButton.Create(panel1);
56          TButton(ctrl).OnClick := CustombuttonClick;
57        end;
58      2: ctrl := TEdit.Create(Panel1);
59      3: ctrl := TLabel.Create(Panel1);
60    else
61      Exit;
62    end;
63    ctrl.Top := FPopupPosition.Y;
64    ctrl.Left := FPopupPOsition.x;
65    ctrl.Parent := panel1;
66    S := ctrl.Classname;
67    Delete(S, 1, 1);
68    i := 1;
69    while panel1.FindComponent(S + IntToStr(i)) <> nil do
70      Inc(i);
71    ctrl.Name := S + IntToStr(i);
72  end;
73  
74  procedure TForm1.Panel1MouseDown(Sender: TObject; Button: TMouseButton;
75    Shift: TShiftState; X, Y: Integer);
76  var
77    p: TPoint;
78  begin
79    if Button <> mbLeft then
80      Exit;
81    FPopupPosition := Point(X, Y);
82    p := (Sender as TPanel).ClientToScreen(FPopupPosition);
83    PopupMenu1.Popup(p.x, p.y);
84  end;
85  
86  function TForm1.Filename: string;
87  begin
88    result := ExtractFilePath(ParamStr(0)) + Name + '.DAT';
89  end;
90  
91  procedure TForm1.SaveButtonClick(Sender: TObject);
92  var
93    fs: TFileStream;
94    i: Integer;
95  begin
96    fs := TFileStream.Create(filename, fmCreate);
97    try
98      fs.WriteComponent(panel1);
99    finally
100     fs.free
101   end;
102   for i := panel1.ComponentCount - 1 downto 0 do
103     panel1.Components[i].Free;
104 end;
105 
106 procedure TForm1.RestoreButtonClick(Sender: TObject);
107 var
108   fs: TFileStream;
109   i: Integer;
110 begin
111   fs := TFileStream.Create(filename, fmOpenread or fmShareDenyWrite);
112   try
113     fs.ReadComponent(panel1);
114     { Note: this will restore all properties of the read objects, 
115 		with the  exception of events. Since the event handlers belong to the form,
116 		not the panel, the reader is unable to resolve the method names to 
117 		method pointers. So we have to reconnect the event here manually. }
118     for i := panel1.ComponentCount - 1 downto 0 do
119       if panel1.Components[i] is TButton then
120         TButton(panel1.Components[i]).OnClick := CustomButtonClick;
121   finally
122     fs.free
123   end;
124 end;
125 
126 procedure TForm1.CustomButtonClick(Sender: TObject);
127 begin
128   ShowMessage((Sender as TButton).Name);
129 end;
130 
131 initialization
132   RegisterClasses([TButton, TEdit, TLabel]);
133 end.
134 
135 ------------------------------------------------------------------------------------
136 ---------
137 object Form1: TForm1
138   Left = 215
139     Top = 109
140     Width = 556
141     Height = 303
142     Caption = 'Form1'
143     Color = clBtnFace
144     Font.Charset = ANSI_CHARSET
145     Font.Color = clWindowText
146     Font.Height = -15
147     Font.Name = 'Arial'
148     Font.Style = []
149     OldCreateOrder = False
150     Scaled = False
151     PixelsPerInch = 120
152     TextHeight = 17
153     object CloseButton: TButton
154     Left = 24
155       Top = 28
156       Width = 75
157       Height = 25
158       Caption = 'Close'
159       TabOrder = 0
160       OnClick = CloseButtonClick
161   end
162   object Panel1: TPanel
163     Left = 112
164       Top = 24
165       Width = 421
166       Height = 237
167       Caption = 'Click me!'
168       TabOrder = 1
169       OnMouseDown = Panel1MouseDown
170   end
171   object SaveButton: TButton
172     Left = 24
173       Top = 60
174       Width = 75
175       Height = 25
176       Caption = 'Save'
177       TabOrder = 2
178       OnClick = SaveButtonClick
179   end
180   object RestoreButton: TButton
181     Left = 24
182       Top = 92
183       Width = 75
184       Height = 25
185       Caption = 'Restore'
186       TabOrder = 3
187       OnClick = RestoreButtonClick
188   end
189   object PopupMenu1: TPopupMenu
190     Left = 112
191       Top = 4
192       object Button2: TMenuItem
193       Tag = 1
194         Caption = 'Button'
195         OnClick = PopupMenuClick
196     end
197     object Edit1: TMenuItem
198       Tag = 2
199         Caption = 'Edit'
200         OnClick = PopupMenuClick
201     end
202     object Label2: TMenuItem
203       Tag = 3
204         Caption = 'Label'
205         OnClick = PopupMenuClick
206     end
207   end
208 end
209 ------------------------------------------------------------------------------------
210 ---------


			
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