WinForm app: Capture a videostream in a new form. Error LNK2005. (developed version)

Question

0.00/5 (No votes)

See more:

Hello,

this version is a developed one for my last question. The errors in the last article are already solved. But a new small bug occurs.
Recently problem: class can only be declared and used within an event.

Code follwing:

CamShow.cpp:

#include "stdafx.h"
#include <DShow.h>
#include <Windows.h>
#include <comdef.h>
#include "CamShow.h"

CamShow::CamShow()
        {		
			pGraphBuilder				= NULL; 
			pCGB					= NULL;
			pCGB2					= NULL;
			......
	}
	CamShow::~CamShow() {}
	
        HRESULT CamShow::InitComLib()
	{
		HRESULT hr = NULL;
		hr = CoInitialize(NULL);
		return hr;
	}
		
	HRESULT CamShow::CaptureVideo(int NO)
	{
		HRESULT hr;
		IBaseFilter *pSrcFilter=NULL;
		......
				}
        //other functions
        //.
        //.
        //.

CamShow.h:

#pragma once //with or without no difference
#include <DShow.h>
#include <Windows.h>
#include <comdef.h>

#define WM_GRAPHNOTIFY  WM_APP+1
enum VIDEOSTATUS {Stopped, Paused, Running, Init};

class CamShow
	{
	public: CamShow(); 
		~CamShow();

	public:	
			HRESULT CamShow::InitComLib();
			HRESULT CamShow::CaptureVideo(int);
			......
                        void CamShow::CoUnini();

      	public:
			IGraphBuilder			*pGraphBuilder;
			ICaptureGraphBuilder		*pCGB;
			ICaptureGraphBuilder2		*pCGB2;
			IVideoWindow			*pVW;
			IMediaControl				*pMC;
			IMediaEventEx				*pME;
                        ......
				
        };

Form1.h:

#pragma once
#include "Form2.h"
......
private: System::Void button1_Click(System::Object^  sender, System::EventArgs^  e) {
                Form^ frm = gcnew Form2();
                frm->Show();
             }
......

Form2.h:

#pragma once
#include "CamShow.h"

namespace LOSCH {

	using namespace System;
	using namespace System::ComponentModel;
	using namespace System::Collections;
	using namespace System::Windows::Forms;
	using namespace System::Data;
	using namespace System::Drawing;
        
        //CamShow test;   
// when i declare a class test, the system error says:
// error LNK2005: "class WebcamShow::CamShow test" (?test@@3VCamShow@WebcamShow@@A) is already in Form2.obj defined.
	
	/// <summary>
	/// Zusammenfassung für Form2
	/// </summary>
	public ref class Form2 : public System::Windows::Forms::Form
	{
		private: System::Void button1_Click(System::Object^  sender, System::EventArgs^  e) {
				CamShow test;
// This works well and I can get the video to be captured on form2
// But the problem is, the test class is only within this section useful,
// e.g. when I want to use another button2_click to stop the preview, I have to make the declaration test again and all initializations and querys etc. there again. At last with pMC->Stop(); ... Which is obviously not good. 
				button1->Enabled=false; 

					hr = test.InitComLib();

					hr = test.GetInterfaces();
                                        .......

}

Posted 5-Oct-12 1:22am

christmars

Add a Solution

2 solutions

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Richard MacCutchan · Answer 1 · 2012-10-05T03:25:00

Solution 1

Try:

C#

public ref class Form2 : public System::Windows::Forms::Form
{
    // make test available to all following methods
    CamShow test;

    private: System::Void button1_Click(System::Object^  sender, System::EventArgs^  e) {

Posted 5-Oct-12 3:25am

Richard MacCutchan

Comments

christmars 5-Oct-12 9:54am

I've tried that, but it still makes error.

Richard MacCutchan 5-Oct-12 12:47pm

And?

christmars 6-Oct-12 4:38am

And the same error...

Richard MacCutchan 6-Oct-12 5:15am

You have a global definition somewhere in your Form2.

christmars 6-Oct-12 5:37am

I've taken the Form2.h in Form2.cpp away. And the global definition of the class works. Do you think this is right in win form app?

Richard MacCutchan 6-Oct-12 11:58am

The issue is that you should have the definition in one place only, so I would say that you are correct.

christmars 8-Oct-12 1:56am

Sorry for my late rely! Thanks!

Maxim Kartavenkov · Answer 2 · 2012-10-06T08:31:00

Solution 2

You have multiply declaration of the variable with same name in the same scope.
Try to use different name of the variable if you need it in scope there you try to declare it.

Like

C++

WebcamShow::CamShow Form2Test;

And use it in you methods in Form2. But better to declare variables in a class not globally.

Regards,
Maxim.

Posted 6-Oct-12 8:31am

Maxim Kartavenkov

Comments

christmars 8-Oct-12 1:53am

Hi Maxim! Firstly sorry for my late reply and thank you so much for your answer. But there's nothing to do with a "different name". That's not the point, I have to say. The problem is that I want to declare and make use of a "global" class and it shows error that the declaration is duplacated.
Form1.cpp/Form1.h includes Form2.h and creates a global CamShow object. Form2.cpp includes also Form2.h and creates another CamShow object with the same name in the same namespace. So I took the Form2.h in Form2.cpp away and it works well.
But actrually I am a Win Form APP beginner. So I'm not sure if this is a right way for stable programms in this windows forms app.

Maxim Kartavenkov 8-Oct-12 2:03am

then you should declare you object in Form1.h as extern: "extern WebcamShow::CamShow test;" - that means object declaration located somethere but not here. In Form1.cpp declare that object: "WebcamShow::CamShow test;" - same line without "extern" and then include your Form1.h there you need your class. - follow?