dbnavigator
lazarus / 16-Databases

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Hansvb · 2014-08-08 21:00

How can i check wich button is clicked on the dbnavigator.

I want to do someting like this:

if dbnavigator button clicked on is next then do something.

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howardpc · 2014-08-08 21:40

Add a private method to your form class
Code: [Select]...
private
  procedure OnNavClick(Sender: TObject; Button: TDBNavButtonType);

Hook it up to your DBNavigator instance in the form's OnCreate
handler:
Code: [Select]procedure TForm1.FormCreate(Sender: TObject);
begin
  ...
  DBNavigator1.OnClick:=@OnNavClick;
  ...
end;

Then implement OnNavClick in some appropriate way as a variation on
this:
Code: [Select]procedure TForm1.OnNavClick(Sender: TObject; Button:
TDBNavButtonType);
begin
  case Button of
    nbFirst, nbPrior: ;
    nbNext: ShowMessage('DBNavigator Next button clicked');
    nbLast..nbRefresh: ;
  end;
end;

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Hansvb · 2014-08-14 09:09

It works great. Thanks.


What does this mean:

Code: [Select] DBNavigator1.OnClick:=@OnNavClick;

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howardpc · 2014-08-14 09:53

OnClick is an event property provided by the designers of TDBNavigator
which is often empty (not used, its value is nil), but which is
available for exactly the situation you want: notification of some
navigator button having been clicked.
If you assign a non-nil value to OnClick, then when the event gets
triggered by a navigator button click, it will call the procedure
which lives at the address you assigned to it.
In objfpc mode you make the assignment using the @ (address-of)
operator.
Code: [Select]  xxx.OnClick:=@MyProcedureThatRespondsToTheClick(arg1,
arg2, arg3 ...);
In Delphi mode you omit the @ operator (because the compiler knows it
is needed, and Delphi's designers thought it was easier on beginner
programmers to leave taking the address as implicit).
You must ensure that the procedure signature is correct (i. e. it has
the correct parameters - usually at least a Sender: TObject - and that
it is a "procedure of object", i. e. declared in a class so that it
carries its own hidden "Self" information). If the method signature is
incorrect, the compiler will choke, pointing out the discrepancy
between what is needed and what you provided. This is one of the
strengths of a strongly-typed langauge such as Object Pascal, and the
value of detailed compiler error-messages which enable you to identify
exactly what is incorrect about your assignment statement.

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rvk · 2014-08-14 13:05

Quote from: howardpc on August 14, 2014, 11:53:01 am...
Beautiful explanation 

But... when using Lazarus/IDE it would be easier to click the
DBNavigator1 and in the Object Insprector select "Events"-tab and
double click "OnClick" and paste the given code (in OnNavClick) into
the newly created procedure TForm1.DBNavigator1Click. It will have the
correct parameters and you don't have to do anything else (no need to
create and assign the methods yourself). The extra code given by
howardpc is necessary when you're creating the components in code.
When using the IDE it's easier to use the Object Inspector.

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tatamata · 2020-03-12 13:55

Procedure that @howardpc provided enables to add additional behavior
to a DBNavigator button.
But, how to force some behavior instead default one for a DBNavigator
button?
For example, I wish to change behavior of nbRefresh button. Instead of
triggering dataset.Refresh method, I would like to change it to
perform dataset.Close followed by dataset.Open statements.
How to accomplish that?

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eljo · 2020-03-12 14:29

Quote from: tatamata on March 12, 2020, 02:55:54 pmProcedure that
@howardpc provided enables to add additional behavior to a DBNavigator
button.
But, how to force some behavior instead default one for a DBNavigator
button?
For example, I wish to change behavior of nbRefresh button. Instead of
triggering dataset.Refresh method, I would like to change it to
perform dataset.Close followed by dataset.Open statements.
How to accomplish that?
use the BeforeAction event and after you executed your code if you do
not want the default code to run raise an EAbort exception.

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tatamata · 2020-03-12 15:01

Quote from: eljo on March 12, 2020, 03:29:52 pmQuote from: tatamata on
March 12, 2020, 02:55:54 pmProcedure that @howardpc provided enables
to add additional behavior to a DBNavigator button.
But, how to force some behavior instead default one for a DBNavigator
button?
For example, I wish to change behavior of nbRefresh button. Instead of
triggering dataset.Refresh method, I would like to change it to
perform dataset.Close followed by dataset.Open statements.
How to accomplish that?
use the BeforeAction event and after you executed your code if you do
not want the default code to run raise an EAbort exception.
Thanks @eljo, you made my day!
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i procedure
TfrmMain.DBNavHackOnClick(Sender: TObject; Button:
TDBNavButtonType);begin  case Button of    nbInsert:      begin      
(Sender as TDBNavigator).DataSource.DataSet.Append;        raise
EAbort.Create('Append hack');      end;    nbRefresh:      begin     
 (Sender as TDBNavigator).DataSource.DataSet.Close;        (Sender as
TDBNavigator).DataSource.DataSet.Open;        raise
EAbort.Create('Refresh hack');      end;  end;end;    procedure
TfrmMain.FormCreate(Sender: TObject); begin     //Hacking
DBNavigators, due to problems with Refresh and Insert vs Append   
 DBNavigator_Projects.BeforeAction := @DBNavHackOnClick;   
 DBNavigator_Solutions.BeforeAction := @DBNavHackOnClick;   end;