How do I use an if statement to get the status of a button that was clicked in a `MessageDlg'?
Heres my code:
if MessageDlg('Message',mtError,[mbYesNoCancel],0) = No
then ShowMessage('Message2');
I saw my IT teacher write something like this a while ago, but I don't remember the syntax.
The documentation says:
MessageDlg returns the value of the button the user selected. The
following table lists the TMsgDlgBtn values for each type of button
that can appear in the message box, and the corresponding value that
is returned if the user selects that button:
TMsgDlgBtn Value Corresponding return value
mbOK mrOk
mbCancel mrCancel
mbYes mrYes
mbNo mrNo
mbAbort mrAbort
mbRetry mrRetry
mbIgnore mrIgnore
mbAll mrAll
mbNoToAll mrNoToAll
mbYesToAll mrYesToAll
mbClose mrClose
So you need to test for mrNo.
I do recommend that you learn where to find documentation to make your life easier.
Related
I'm using Dephi 10.1 Berlin and Access 2013.
My problem is related to TADODataSet.Cancel().
I want to show my user a message box asking for a confirmation before posting, in case data has been modified.
In the TADODataSet.BeforePost event, I added the following code:
if Application.MessageBox('Save changes?', '', 52) = idNo then
ADODataSet1.Cancel;
If the user click on btnNo, something unexpected happens.
Changes are canceled from the current record, but a new record with all fields empty is created.
The only field with some data is the one that was previously modified by the user.
If I cancel the modification via the cancel button of TDBNavigator, everything is fine.
If I simulate a click of the Cancel button of the TDBNnavigator in the BeforePost event:
if Application.MessageBox('Save changes?', '', 52) = idNo then
DBNavigator1.BtnClick(nbCancel);
I have the same behaviour, so a new empty record is created.
Any suggestion?
The help for TADODataSet.BeforePost says in part:
call Abort to cancel the Post operation (Delphi) or throw an exception (C++).
So:
if Application.MessageBox('Save changes?', '', 52) = idNo then
abort;
Note this is meant for preventing changes that don't pass validation (the common use for BeforePost) from being posted. It doesn't reset the edit buffers like cancel does. Usually that is a separate function in the UI so the user doesn't have to reenter all the changed data in the edits each time posting is rejected by calling abort in BeforePost.
I write this code for button click event . the first time I click the button every thing work correctly but when click for the second time on button it raise an error. whats the problem?
procedure TfrmMain.Button1Click(Sender: TObject);
var
B : Boolean;
begin
DM.tblTemp.DisableControls;
B:= DM.tblTemp.Locate('FoodName', DM.tblAsli.FieldByName('FoodName').AsString,[]) ;
if B then
begin
DM.tblTemp.Edit;
DM.tblTemp.FieldByName('Number').AsInteger:= DM.tblTemp.FieldByName('Number').AsInteger + 1;
DM.tblTemp.Post;
end
else
begin
DM.tblTemp.insert;
DM.tblTemp.FieldByName('FoodName').AsString := DM.tblAsli.FieldByName('FoodName').AsString;
DM.tblTemp.FieldByName('UnitPrice').AsInteger := DM.tblAsli.FieldByName('FoodPrice').AsInteger;
DM.tblTemp.FieldByName('Number').AsInteger := 1;
DM.tblTemp.Post;
end;
TotalPrice:= TotalPrice + DM.tblTemp.FieldByName('TotalPrice').AsInteger;
DM.tblTemp.EnableControls;
end;
the Error is
Row cannot be located for updating. Some values may have been changed
since it was last read
DM is data madual
tmbTbl is ADOTable
It is a pity you haven't said which DBMS you are using (e.g. Sql Server or MS Access,
nor told us a full list of the table's column types and indexes, if any.
The most likely answer to your q is that the variable B is set to False the first time
because the call to tblTemp.Locate fails to locate the Food name in question, so the Insert branch executes and the food's data is
added to the table but the second time the Edit branch executes and the error occurs,
though you have not said where, exactly. My guess would be on the call to .Post, because
the error message is one the ADO layer, which sits between the DBMS provider and your app,
emits when it attempts to post a change to the table but cannot identify which table row to update.
As I mentioned in a comment, the fix to this is usually at add a primary key index to the table, and I gather from your latest comment that this has succeeded for you. For the record and benefit of future readers it would be helpful if you could confirm which DBMS you are using and which Ole Driver you are using in your connection string.
Fwiw, I've tested your code using a table on MS Sql Server and MS Access and do not get the
error with either database.
Btw there is an obvious q, "How is it that tblTemp.Locate succeeds, but ADO is unable to
identify the correct record to post the update?" The answer is that tblTemp.Locate works in
a different way than identifying the relevant row to post the update.
I'm using C++Builder 10.3 with a VCL application for Windows. I'm trying to identify a specific item in an AdvPopupMenu by looping through the Items Caption and comparing the Caption to my search text using CompareText(). The Captions have an '&' in the Caption text which I believe is part of the ShortCut feature. This seems to prevent a match when comparing the text.
I have tried setting up the menu items two ways to try and remove the '&'.
//--#1 Menu Setup--
TMenuItem *NewMenuItem;
NewMenuItem = new TMenuItem(MainForm->AdvPopupMenu1);
TShortCut sc2;
sc2 = TextToShortCut("(None)");
NewMenuItem->Caption = "Google";
NewMenuItem->ShortCut = sc2;
//--#2 Menu Setup--
TMenuItem *NewMenuItem;
NewMenuItem = new TMenuItem(MainForm->AdvPopupMenu1);
NewMenuItem->Caption = "Google";
NewMenuItem->ShortCut = NULL;
Below is my loop to search for the AdvPopupMenu item.
UnicodeString SearchFor = "Google";
UnicodeString TestCaption;
for(int i=0; i<MainForm->AdvPopupMenu1->Items->Count; i++){
TestCaption= MainForm->AdvPopupMenu1->Items->Items[i]->Caption;
if(CompareText(SearchFor , TestCaption)==0 ){
//This CompareText always fails
//TestCaption looks like this "&Google" or this "G&oogle"
}
}
How can I setup the AdvPopupMenu Caption to contain no '&' and make the CompareText work?
The &s are important. Without these, keyboard users like myself will find your application more difficult to use.
I think your best solution is to use the StripHotkey function in the Vcl.Menus unit to remove the ampersand character before you pass the caption to CompareText. (In addition, instead of testing if CompareText returns 0, it's better to use the SameText function.)
That is, don't attempt to create the menu items without the ampersand character, and don't try to remove it from the menu items. Only remove the character from the string you pass to the comparison function.
Also notice that the ampersand character is not related to the ShortCut property. The ampersand character makes the next character underlined in the menu item caption, telling the user than he or she can press that key to activate the menu item, but only when the menu is open. On the other hand, the ShortCut property adds a right-aligned text like Ctrl+A or Shift+Ctrl+N or F2 to the menu item, and these shortcuts are available even when the menu isn't open. Hence, these are different features.
(Delphi 6 with TChart, Win XP)
I'm getting erratic behavior trying to clear the points from a point series, and of course, this code used to work.
Basically, this part of my program generates 5 data points and plots them. When I try to clear them using OSC_Series.Clear I get a "List index out of bounds [0]" error.
I checked to make sure there was nothing odd about the values I was plotting. All is good there. Then I tried different things to try to isolate and work around the problem.
Here's some code.
type
TksGraph_DataFrm = class(TForm)
.
.
.
private
OSC_Series: TPointSeries
public
end;
procedure TksGraph_DataFrm.cat7AnalysisInitialize(var P:TTest_Project);
begin
// Do a bunch of stuff.
// Set up the analysis data points series.
OSC_Series:=TPointSeries.Create(self);
AnalysisChart.AddSeries(OSC_Series);
with OSC_Series do
begin
Title:='';
HorizAxis:=aBothHorizAxis;
VertAxis:=aBothVertAxis;
SeriesColor:=clRed;
Pointer.Brush.Color:=clYellow;
Pointer.HorizSize:=4;
Pointer.VertSize:=4;
Pointer.Style:=psRectangle;
Pointer.Visible:=true;
LinePen.Color:=clBlack;
LinePen.Width:=1;
Linepen.Visible:=true;
ShowInLegend:=false;
XValues.Order:=LoNone;
end;
end;
procedure TksGraph_DataFrm.cat7AnalysisRefresh(var P:TTest_Project);
var X,Y:single;
begin
X:= some value
Y:= some value
// Plot the result.
OSC_Series.AddXY(X,Y);
showmessage(
'Count = '+inttostr(OSC_Series.Count)+#13+
'X = '+FloatToStr(X)+#13+
'Y = '+FloatToStr(Y)+#13+
'Plot-X = '+FloatToStr(OSC_Series.XValue[OSC_Series.Count-1])+#13+
'Plot-Y = '+FloatToStr(OSC_Series.YValue[OSC_Series.Count-1]));
end;
Here is the routine I to use to reset the series. I'm including code that does and does not work.
procedure TksGraph_DataFrm.cat7AnalysisClear(var P:TTest_Project);
var i:integer;
begin
// This should work, but it gives me the list out of bounds error
// unless the count is 0.
OSC_Series.Clear;
// This does not work, for obvious reasons. I get a "list out of
// bounds [3] for this one.
for i:=0 to OSC_Series.Count - 1 do OSC_Series.Delete[0];
// It seems this should work, but again I get the out of bounds [0]
// error.
repeat
OSC_Series.Delete(0);
until OSC_Series.Count = 0;
// This works. Don't ask me why.
showmessage('A - '+inttostr(OSC_Series.Count));
OSC_Series.Clear;
showmessage('B - '+inttostr(OSC_Series.Count));
// This also works.
sleep(2000);
OSC_Series.Clear;
// This does not work.
sleep(1000);
OSC_Series.Clear;
end;
I'm stumped, obviously.
This smells like the code is working with an object (OSC_Series) which has been destroyed and the memory then re-used for something else. When you then use the stale reference to that memory you get unexpected and unpredictable results.
Where is OSC_Series free'd ?
I would check all such places and make sure that you do not attempt to use the OSC_Series reference after it has been free'd.
Note also that since the series is owned by the form it could be that the form itself is contriving to executing code in events after it has destroyed its owned components (including this series).
OK, dumb and not dumb.
I experimented with where I put the showmessage statement. I found I could only avoid the error if that statement came after the OSC_Series.Clear statement. I kept moving that statement back until it was after the call to the AnalysisRefresh routine, which is in a button's OnClick event handler. This means that none of the code in the refresh, enable, or update routines was causing this.
Stepping back a bit, if the AnalysisRefresh routine fails the user is shown a message. After that box is closed OSC_Series.Clear is called. If I close the box by pressing SPACE or ENTER on the keyboard... no error. If I use the mouse, error.
The chart behind the mouse has an OnMouseMove event where I display the mouse position on a status bar. I also display a hint if the mouse is near a plotted point. After clicking the message box with a mouse to close it the OnMouseMove event is called and by the time it gets to where it can display the hint, the plotted point is gone, and... error.
So, it seemed like an almost random error, but it wasn't. The trigger was just somewhere else entirely. That's you my try/except block wasn't catching the error. EurekaLog was catching it, but in a different procedure far, far away. (Deltics' answer was pretty close.)
Thanks for your help and suggestions.
Dang it if some days I can push hundreds of lines of code with no problems, then something like this pops up and it costs me near two days.
I just used the SecondaryShortCuts-Feature of Delphi's TAction. But Shortcuts are defined by Strings, like "F5" or "Shift+F5". Now the problem: On my German Windows the action doesn't fire, because the key "Shift" is called "Umsch" in German!
Does it mean the SecondaryShortCuts-Property is completely useless at design time, because nobody can create applications which work internationally with that?
I could set the key at runtime by translating the VK_SHIFT into the correct name. I tried it via GetKeyNameText but this didn't worked because it gave the long form "Umschalt" not "Umsch". Anybody know the function to get the short version of the key name?
You could try this: Generate the shortcut text from a shortcut:
var
s: TShortCut;
begin
s := ShortCut(Ord('A'), [ssShift]);
Action1.SecondaryShortCuts.Add(ShortCutToText(s));
By the way, these values are determined by the following constants. Have you translated those? And if so, do you need to?:
SmkcShift = 'Shift+';
SmkcCtrl = 'Ctrl+';
SmkcAlt = 'Alt+';