C++ / JNI object instance problems - C / C++ / MFC Discussion Boards

Shouldn't cause an accvio, though - you can delete NULL in C++.

but will result in a memory leak.

This signature was proudly tested on animals.

I didn't say it wouldn't - I was just saying that fixing it wouldn't solve the OP's problem.

Thanks a lot

Yes, but Carlo just indicated one of flaws in the OP's code. I agree that it wouldn't solve 'the problem' of the OP, but it might (hopefully) prevent the OP from shooting his own face sometime in the future. Smile | :)

It is a crappy thing, but it's life -^ Carlo Pallini

i havent any problem with new delete , occur exception even this case

void CUseTestLibDlg::OnBinitlib2() 
{
	CTest  pcTest;	
}// Unhandled exception in UseTestLib.exe: 0xC0000005: Access Violation.

The problem's obviously in CTest's destructor. The only significant activity in CTest's destructor will be calls to m_str1's and m_str2's destructors. Therefore, the access violation is happening somewhere in there.

I suspect there's something not quite right with your project settings - check that the library and main app are using hte same MFC and C run-time library settings.

I have just started at a new job. Here we are new to using JNI ( for bridging C++ / Java ). I am new to JNI so please forgive my noobness Smile | :)

In our (win32) Java app we are loading a C++ DLL. On the Java side we have several instances of "SomeJClass" each of these instances needs access to corresponding instance of "SomeCClass" on the DLL side. The DLL exposes entry-points such as GlobalDoSomethingInC(). Here I must call the instance method of Doer::DoSomethingInC(). So I need a smooth way to map the respective this-pointers. I also need to do the same mapping when a DLL thread discovers something interesting that it needs to notify the corresponding Java-instance of.

I can think of several solutions, but I do not like them too much. My question is, is there a better way than this ?

1 Java calls C:GetNewInstance(). This returns an int that is actually a pointer to the new C instance. Java stores it in m_myCInstance. Then Java calls GlobalDoSomethingInC(), and 1a

// DLL global<br />
void GlobalDoSomethingInC()<br />
{<br />
    // retrive this pointer<br />
    //calling back to Java:  <br />
    jobj tmpJ = NewGlobalRef( env, obj );<br />
    Doer* myDoer = <reinterpret_cast>( Doer )tmpJ->GetMyCInstance();<br />
    myDoer->DoSomething();<br />
    DeleteGlobalRef( env, tmpJ );<br />
    // Arrrrgh<br />
}<br />
</reinterpret_cast>

1b or:

    // for **every call** that Java adds a parameter, <br />
    //which is the stored int:m_myCInstance, and<br />
    Doer* myDoer = <reinterpret_cast>( Doer )instanceParam->DoSomethingInC();<br />
    // Can we do better that this?<br />
<br />
</reinterpret_cast>

2 For calling from C to Java, things look, maybe, better

In the constructor C calls back into Java and stores
the Java instance reference

in a member variable. m_myJInstance.<br />
In all subsequent calls m_myJInstance can be used to call back Java.<br />
In the destructor we need to call DeleteGlobalRef( env, m_myJInstance );<br />

Not too bad I suppose. But it really safe to store the jobject reference. I mean: What happens when the GC moves the object around?

3 Our present solution does "work". But it belongs on rather on http://www.codinghorror.com/blog/ Smile | :)

Another question, for JNI experts only. How much juice does it cost to do this sequence:

<br />
    jobj tmpJ = NewGlobalRef( env, obj );<br />
    tmpJ->GetMyCInstance();<br />
    DeleteGlobalRef( env, tmpJ );

Thanks
Adam

........................
Life is too shor

I have a MDI application which has several document types. And I am adding sub-menus dynamically for some of the document types. The follwoing is the code snippet

class CMyMenu: public CMenu
{
int data1;
...
public:
virtual ~CMyMenu(){};
};

Then in the mainframe I declare a function AddNewMenu
CMainFrame::AddMenu(HMENU hMenu)
{

CMyMenu *pMenu = (CSMenu*)CSMenu::FromHandle( toolbarMenu );

CMyMenu* popup1 =

new CSMenu(), *popup2 = new CSMenu();

//create the two pop-up menus
createPopup1(&popup1);
createPopup2(&popup2);

pMenu ->AppendMenu( MF_POPUP, (UINT)popup1->GetSafeHmenu(), "Popup1" );
pMenu ->AppendMenu( MF_POPUP, (UINT)popup2->GetSafeHmenu(), "Popup2" );

...
}

My question is if I call ::DestroyMenu(hMenu) later on, it will delete all the submenus but will it delete the associated "CMyMenu" objects too or do I have to save both popup1 and popup2 to delete the objects my self

Please reply
Thanks

Farhat Aisha wrote:
My question is if I call ::DestroyMenu(hMenu) later on, it will delete all the submenus but will it delete the associated "CMyMenu" objects too or do I have to save both popup1 and popup2 to delete the objects my self

Well I guess you can either choose to believe the documentation, or not. If you don't believe it then you can perform some tests to see if it leaks.

DestroyMenu[^]

Remarks

Before closing, an application must use the DestroyMenu function to destroy a menu not assigned to a window. A menu that is assigned to a window is automatically destroyed when the application closes.

DestroyMenu is recursive, that is, it will destroy the menu and all its submenus.

Hi,
Actually i need to vanish the 'X'-box from the system menu & keep only Minimize-Box in the menu bar.
I'hv used a code stuff under OnInitDialog()---
CMenu* cmenu = this->GetSystemMenu(FALSE);
cmenu->ModifyMenu(SC_CLOSE,MF_BYCOMMAND | MF_GRAYED);

OR

CMenu* cmenu = GetSystemMenu(FALSE);
cmenu ->RemoveMenu(SC_CLOSE,MF_BYCOMMAND );
cmenu ->RemoveMenu(0,MF_BYPOSITION);

==>In both cases ,it only disabling the X-box not vanishing from the menu bar.

So is there any way to totally clear this X-box.
If then plz repay as soon as possible.

Thanks in advance Smile | :)

You could modify the code in this article[^] (see the PaintCap.h and PaintCap.cpp files in the file linked from the article) to draw the title-bar yourself. That way you can decide exactly which boxes to draw...

Shashi.Shinde wrote:
So is there any way to totally clear this X-box.

Not without removing the entire system menu, or drawing it yourself.

"Old age is like a bank account. You withdraw later in life what you have deposited along the way." - Unknown

"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons

[Message Deleted]

Please rephrase your query such that people can understand it. Also, the 'bold' font face doesn't particularly look charming.

It is a crappy thing, but it's life -^ Carlo Pallini

[Message Deleted]

I see nothing different, other than some changes in font styling. If you can explain your difficulty better, I will be in a position to understand it and possibly offer you help.

It is a crappy thing, but it's life -^ Carlo Pallini

Purish Dwivedi wrote:
I have created a multilingual application. When I am changing the language, the old language characters are not remove,while new language character is being overwritten.

Well, I suppose this is the true spirit of a MULTIlingual application.

BTW We're really genii, and we might guess your problem and find the solution without even seeing a single line of your code. Unfortunately we cannot fully exploit our superpowers here, to not shock the mean people.
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke

[My articles]

[Message Deleted]

Purish Dwivedi wrote:
WOW,
What an answer.

Well, question helped.
Big Grin | :-D

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke

[My articles]

In French we have an expression: "A question stupide, réponse stupide", which translates to "Stupid question, stupid answer". I think it makes complete sense here Smile | :)

Cédric Moonen
Software developer

Charting control [v2.0]
OpenGL game tutorial in C++

In Italy we have a similar expression: "A domanda stupida, risposta intelligente" (well, I twisted a bit... Roll eyes | :rolleyes:

).

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke

[My articles]

[Message Deleted]

Are you about to ~~deleting~~ delete that message too?
Smile | :)

[added]
I suppose my guess was correct... Roll eyes | :rolleyes:

[/added]

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke

[My articles]

modified on Wednesday, April 29, 2009 6:26 AM

Hello Friends
How can i add text just with Mouse Cursor.Actually i m writing one case on MOUSEMOVE.So i want to display X and y Coordinates with Mouse Cursor.I m getting X and y Coordinates.But how to add with mouse cursor.

Thanks & Regards
yogesh