This is a simple question.
Start a multidevice App, place a TDateEdit and DBTable with a field containing TdateTime data. Then use LiveBinding designer link the data source field to TDateEdit.DateTime property. However, this link is unidirectional , The control DateEdit can accept the data from the Datasource, but cannot update the changes to the datasource. How to change the link to bidreiction???
There may be some things that are not clearly understood.
Normally a LiveBindings link will be bidirectional - so if you setup two TDateEdits and bind them together changing one should change the other, irrespective of which one you change.
It seems that what you are hoping is that changing the TField will update the data in the database table.
That's not typically how the Data Access components in Delphi work.
The TField is part of a TDataSet. The TDataSet has a Post method to write changes to the underlying data store, if that's supported.
The Data Access components are extremely powerrful and can cope with lots of different scenarios, and allow you to extended capabilities throguh exposed events as well as subclassing the components.
If you want to update your underlying data store you need to have a writeable TDataSet and you need to call Post on it to write.
I suggest you start off with some of the videos in Enbarcadero's YouTube channel about how to use the data acecss components. It's not difficult to do but beyond the scope of an answer here.
If you use the LiveBindings Wizard to hook the DateEdit with a field, it will hook it up bi-diretionally to a "virtual" SelectedDateTime property of the DateEdit. That property doesn't really exist in the TDateEdit but is used by the LiveBindings to map the separate Date and Time properties of the DateEdit.
I want to load the content of of dbctrlgrid at runtime (from database). So I encountered several challenges:
How to detect if the dbctrlgrid is empty and/or how to clear it.
How to put Tlabel and Tdbtext on the panel. The main problem seems to be to find the right parent. dbctrlgrid doesn't work. There is an object called Tdbctrlpanel which should work, but I don't know how to access it. I could not find it in properties or methods of Tdbctrlgrid.
Any code snipplet is welcome
To answer 1)
You don't query the TDBCtrlGrid, you query the underlying dataset; if it .IsEmpty the grid is empty.
When people start using data aware (grid) components they have the tendency to see that as the 'data container' that you can query and modify, but that is not the case. See it as a view on your underlying data with some built-in editors that modify that data. Then the 'same rules' apply to you as to these editors: update the underlying dataset.
To add controls to a TDBCtrlGrid you have to set the controls parent to the Panel property of the TDBCtrlGrid. The problem is that this property is protected. There are several ways to overcome this limitation. One is shown at Delphi About: Accessing protected members of a component
This is a common technique known to Delphi programmers as the 'protected hack'.
We are creating a component and want to mimic the concept behind Designer.GetComponentNames, where as we give can obtain a list of the available components on the form or any form in the uses. We haven't been able to get to the root of GetComponentNames. Any input would be much appreciated.
LE: Actually I take that back. I need this from the design time aspect.
Runtime? You have the Vcl.Forms.TScreen.Forms array for all the displayed forms, and you have Vcl.Forms.Application.Components containing all your forms IIRC. Then, each form has a Components array.
If I understand the first part of your question, you want to get a list of components owned by a form (by name) at designtime.
As background, I have a non-visual component (Call it TColorEdits.) that manages the colors of selected TWinControls on a form at runtime. This component has a TStrings property that contains the names of selected TWinControls on the form. The names of TWinControls to be managed may be selected at designtime using a dialog (dlgEditColors) that contains a couple listboxes, one of which is named DstList and shows all TWinControls available for management by TColorEdits.
So, here is some (simplified) code I use to get the names of TWinControls on a form at designtime and load the TWinControl names into DstList.
{ Load names of TWinControls owned by a form into TListBox DstList }
for i := 0 to TColorEdits(GetComponent(0)).Owner.ComponentCount - 1 do
if ((TColorEdits(GetComponent(0)).Owner.Components[i] is TWinControl) then
dlgEditColors.DstList.Items.Add(TColorEdits(GetComponent(0)).Owner.Components[i].Name);
You should be able to adjust the above code as part of a custom property editor for your component. Hope this helps with the first part of your question.
I have a memory structure which is (pretty much) static and read-only. I would like to present its data as a TDataSet descendent to enable me to use DB grids etc to view / report the data. I have no need of editing (in fact this must be prohibited). I've see this SO question and other advice that some home-rolled code 'has problems with bookmarks'. I really only want a simple solution and ideally this would be where I could create a simple 'virtual' table with my known field types and then be given an 'OnGetFieldData' event for each one. My other choice is to use a DevExpress TDxMemData in-memory table and populate it on changes in my data but this is less efficient and more messy. Is there any other solution?
Don't use TDataSet descendant, use LiveBindings instead. Your situation is exactly what they were created for. Here are some videos about their use: http://www.embarcadero.com/coderage/sessions
I am starting to learn Delphi. So I decided to write an application like MS Excel from scratch. In a new Form1, I did put a TPageControl component containing only 1 page. In that page, I did put a TAdvStringGrid and a TPanel with some buttons (button1, button2) and a Popup1 menu for defining some actions on the grid, like copy cell, copy row, delete row, etc. For that StringGrid, also, I have defined some properties, like colors, fonts, etc. I added a toolbar with a button to the main form, in order to add more pages to the PageControl. The OnClick method of that button defines two actions:
1) to add a new Page2 to the PageControl, and
2) to add a new StringGrid In the new created Page2 .
That new (runtime defined) StringGrid created in a new Page of a Tpagecontrol should inherite (get, copy, clone, duplicate) the properties and methods of the StringGrid parent already defined in the first page at design time, and should be able to call the PopUp1 menu just like the StringGrid parent. How we do this?
At the beginning, I thought I just should copy the StringGrid properties using assing(), but when using this approach, the popup menu does not pop up when right mouse clicking on the new StringGrid... and the buttons (button1 and button2) of Form1 only work with the first StringGrid but not with the new added one. I did read somewhere that in order to solve this problem, I could duplicate the StringGrid component by using the write and read TMemoryStream (save the parent stringgrid into a memorystream, create a new stringgrid and then read that memorystream into the new created stringgrid), so I did, but when the program executes this component cloning method, I get a runtime error. :-(
I did carefully chech the Help. Nothing found on that topic. Seems there is not any Delphi component library or third party components that cope with this kind of task. Can anybody help, please? :o)
I would use an tabcontrol instead of an pagecontrol. That way, you would end up with multiple tabs but only one page and grid. I would then make some kind of data structure to keep all my cell information in, and render this structure to the grid. This way, I can have multiple structures, and let the active tab decide which structure to render. You will also end up with a looser coupling between your gui and your logic, making it easier change things later. E.g. if you need to bring in some values form a different spreadsheet into a cell in the current spreadsheet, you can load up a structure and pick out the wanted values. No need to make any gui for the second spreadsheet at all.
For a 3.party component, I will recommend TMS FlexCell and TAdvSpreadGrid. That will give you most of what you need.
A tricky choice for a learner :) however you do not need to start streaming things.
Look up the assign() procedure for TPersistent this is the routine you need to copy parts of the grid easily. For example
for i := 0 to StringGrid1.RowCount - 1 do
StringGrid2.Rows[i].Assign(StringGrid1.Rows[i]);
for an easy start differentiate your grids with the Tag property(StringGrid1.Tag := 1, StringGrid2.Tag := 2 Etc.
The popup menu is pretty simple too:
StringGrid2.popupmenu := stringGrid1.popupMenu But then then you must decide in the Popup Routine Which Grid is "Active" some thing l like
Tform1.popupMenuItem1Click(Sender: TObject)
if Sender is TStringGrid then
Case TStrigngGrid(Sender).Tag of
1: // Grid 1
2: // Grid 2
You can use the same simple logic with the buttons.
As neftali mentioned the best thing would be to put the created grids in an ObjectList.
You would then end up with the slightly more complex but expandabe:
Tform1.popupMenuItem1Click(Sender: TObject)
var AGrid: TStringGrid;
if Sender is TStringGrid then
AGrid := MyListOfStringGrids[MyListOfStringGrids.IndexOf(Sender)];
DoMenuItem1Stuff(AGrid);
Have fun
"...and the buttons (button1 and button2) of Form1 only work with the first StringGrid but not with the new added one. I did read somewhere that in order to solve this problem..."
There is no generic method for solving this. Delphi offers different tools to solve it.
You can create a list of Objects (TObjectList) that containts all the StringGrid; At Button1 Click event you must search what is the grid that you are using at this moment. For example (BIS for the other buttons):
var
index:integer;
sg:TStringGrid;
begin
...
// search the active page
index := pageControl.ActivePageIndex; //0, 1, 2,...
// USe this for search the StringGrid
sg := TStringGrid(OList.Objects[index]);
// the code that you have at the event bus woking with sg
// not stringgrid1, stringgrid2,...
...
sg.Color :=
...
If you don't want use ObjectList, there are alternatives. You can use Tag property for all StringGrids. Assign 0, 1, 2, 3,...
Extract the index (active page) and search the TStringGrid that have the property Tag with the same value. You can do this with FindComponent. The first methos is better. ;-)
Regards.
P.D: Excuse for my bad english.
Dear all, I am trying to learn Delphi
The Delphi style is to find/create/buy a component that does the job and use them in the design-time. You could try making a custom component based on a grid or use TFrame. See links from Custom Component Development and help files that comes with Delphi.
If you really need to clone the control dynamically, here's an example I found that uses stream.ReadComponent.