我现在有一个线程一直在修改一个全局变量,比如线程一直将变量a赋值为1,然后我现在想通过一个按钮事件,点击一下就先打断线程,将a赋值为2进行一些数据处理,处理完后再交还线程继续为1,写了一个模拟的程序,大概如下HANDLE hEvent = NULL;void adddata();
BOOL bTrun = true;
int a =0;
void ListenerProcess(LPVOID lpParameter) //用于监听文件夹中是否有新文件需要更新
{
while(bTrun)
{
if(WaitForSingleObject(hEvent, INFINITE) == WAIT_OBJECT_0)
{
a = 1;
}
adddata();
}
ExitThread(0);
}void adddata()
{
ResetEvent(hEvent);
if(a == 2)
{
::MessageBox(NULL,"进入了","进入了",MB_OK);
}
SetEvent(hEvent);}//然后按钮点击置为2
void CTestDlg::OnButton1()
{
if(WaitForSingleObject(hEvent, INFINITE) == WAIT_OBJECT_0)
{
a = 2;
}
}这样做结果还是概率性成功,请大虾赐教
BOOL bTrun = true;
int a =0;
void ListenerProcess(LPVOID lpParameter) //用于监听文件夹中是否有新文件需要更新
{
while(bTrun)
{
if(WaitForSingleObject(hEvent, INFINITE) == WAIT_OBJECT_0)
{
a = 1;
}
adddata();
}
ExitThread(0);
}void adddata()
{
ResetEvent(hEvent);
if(a == 2)
{
::MessageBox(NULL,"进入了","进入了",MB_OK);
}
SetEvent(hEvent);}//然后按钮点击置为2
void CTestDlg::OnButton1()
{
if(WaitForSingleObject(hEvent, INFINITE) == WAIT_OBJECT_0)
{
a = 2;
}
}这样做结果还是概率性成功,请大虾赐教
{
if(WaitForSingleObject(hEvent, INFINITE) == WAIT_OBJECT_0)
{
a = 1;
}
adddata();
}
ExitThread(0);你这个事件又是怎么触发的,这要想清楚
然后 WaitForSingleObject()成功后 自动重置的内核事件会被自动设为无信号状态,不需要调用ResetEvent()。
再就是 OnButton1等待成功后根本没有把事件设为有信号状态。
最最重要的是 在WaitForSingleObject和ResetEvent之间的操作时不会被等待同一个事件的线程打断的。按照这种思路,这个程序永远不会成功。偶尔成功是因为你实际上根本没有完成线程同步的操作。
void ListenerProcess(LPVOID lpParameter) //用于监听文件夹中是否有新文件需要更新
{
while(bTrun)
{
if( pause == 0)
{
if(WaitForSingleObject(hEvent, INFINITE) == WAIT_OBJECT_0)
{ a = 1; }
adddata();
}
}
ExitThread(0);
}
//然后按钮点击置为2
void CTestDlg::OnButton1()
{
pause = 1;
if(WaitForSingleObject(hEvent, INFINITE) == WAIT_OBJECT_0)
{ a = 2; }
pause = 0;
}
HANDLE hEvent = NULL;
int pause =0;
void adddata();
BOOL bTrun = true;
int a =0;
void ListenerProcess(LPVOID lpParameter) //用于监听文件夹中是否有新文件需要更新
{
while(bTrun)
{
if( pause == 0)
{
if(WaitForSingleObject(hEvent, INFINITE) == WAIT_OBJECT_0)
{
a = 1;
}
}
adddata();
}
ExitThread(0);
}void adddata()
{
ResetEvent(hEvent);
if(a == 2)
{
::MessageBox(NULL,"进入了","进入了",MB_OK);
}
SetEvent(hEvent);
}
class CAboutDlg : public CDialog
{
public:
CAboutDlg();// Dialog Data
//{{AFX_DATA(CAboutDlg)
enum { IDD = IDD_ABOUTBOX };
//}}AFX_DATA // ClassWizard generated virtual function overrides
//{{AFX_VIRTUAL(CAboutDlg)
protected:
virtual void DoDataExchange(CDataExchange* pDX); // DDX/DDV support
//}}AFX_VIRTUAL// Implementation
protected:
//{{AFX_MSG(CAboutDlg)
//}}AFX_MSG
DECLARE_MESSAGE_MAP()
};CAboutDlg::CAboutDlg() : CDialog(CAboutDlg::IDD)
{
//{{AFX_DATA_INIT(CAboutDlg)
//}}AFX_DATA_INIT
}void CAboutDlg::DoDataExchange(CDataExchange* pDX)
{
CDialog::DoDataExchange(pDX);
//{{AFX_DATA_MAP(CAboutDlg)
//}}AFX_DATA_MAP
}BEGIN_MESSAGE_MAP(CAboutDlg, CDialog)
//{{AFX_MSG_MAP(CAboutDlg)
// No message handlers
//}}AFX_MSG_MAP
END_MESSAGE_MAP()/////////////////////////////////////////////////////////////////////////////
// CTestDlg dialogCTestDlg::CTestDlg(CWnd* pParent /*=NULL*/)
: CDialog(CTestDlg::IDD, pParent)
{
//{{AFX_DATA_INIT(CTestDlg)
// NOTE: the ClassWizard will add member initialization here
//}}AFX_DATA_INIT
// Note that LoadIcon does not require a subsequent DestroyIcon in Win32
m_hIcon = AfxGetApp()->LoadIcon(IDR_MAINFRAME);
}void CTestDlg::DoDataExchange(CDataExchange* pDX)
{
CDialog::DoDataExchange(pDX);
//{{AFX_DATA_MAP(CTestDlg)
// NOTE: the ClassWizard will add DDX and DDV calls here
//}}AFX_DATA_MAP
}BEGIN_MESSAGE_MAP(CTestDlg, CDialog)
//{{AFX_MSG_MAP(CTestDlg)
ON_WM_SYSCOMMAND()
ON_WM_PAINT()
ON_WM_QUERYDRAGICON()
ON_BN_CLICKED(IDC_BUTTON1, OnButton1)
//}}AFX_MSG_MAP
END_MESSAGE_MAP()/////////////////////////////////////////////////////////////////////////////
// CTestDlg message handlersBOOL CTestDlg::OnInitDialog()
{
CDialog::OnInitDialog(); // Add "About..." menu item to system menu. // IDM_ABOUTBOX must be in the system command range.
ASSERT((IDM_ABOUTBOX & 0xFFF0) == IDM_ABOUTBOX);
ASSERT(IDM_ABOUTBOX < 0xF000); CMenu* pSysMenu = GetSystemMenu(FALSE);
if (pSysMenu != NULL)
{
CString strAboutMenu;
strAboutMenu.LoadString(IDS_ABOUTBOX);
if (!strAboutMenu.IsEmpty())
{
pSysMenu->AppendMenu(MF_SEPARATOR);
pSysMenu->AppendMenu(MF_STRING, IDM_ABOUTBOX, strAboutMenu);
}
} // Set the icon for this dialog. The framework does this automatically
// when the application's main window is not a dialog
SetIcon(m_hIcon, TRUE); // Set big icon
SetIcon(m_hIcon, FALSE); // Set small icon
pThread = AfxBeginThread( (AFX_THREADPROC)adddata,
NULL,
THREAD_PRIORITY_NORMAL,
0,
0,
NULL);
hEvent = CreateEvent(NULL,TRUE,TRUE,NULL);
// TODO: Add extra initialization here
return TRUE; // return TRUE unless you set the focus to a control
}void CTestDlg::OnSysCommand(UINT nID, LPARAM lParam)
{
if ((nID & 0xFFF0) == IDM_ABOUTBOX)
{
CAboutDlg dlgAbout;
dlgAbout.DoModal();
}
else
{
CDialog::OnSysCommand(nID, lParam);
}
}// If you add a minimize button to your dialog, you will need the code below
// to draw the icon. For MFC applications using the document/view model,
// this is automatically done for you by the framework.void CTestDlg::OnPaint()
{
if (IsIconic())
{
CPaintDC dc(this); // device context for painting SendMessage(WM_ICONERASEBKGND, (WPARAM) dc.GetSafeHdc(), 0); // Center icon in client rectangle
int cxIcon = GetSystemMetrics(SM_CXICON);
int cyIcon = GetSystemMetrics(SM_CYICON);
CRect rect;
GetClientRect(&rect);
int x = (rect.Width() - cxIcon + 1) / 2;
int y = (rect.Height() - cyIcon + 1) / 2; // Draw the icon
dc.DrawIcon(x, y, m_hIcon);
}
else
{
CDialog::OnPaint();
}
}// The system calls this to obtain the cursor to display while the user drags
// the minimized window.
HCURSOR CTestDlg::OnQueryDragIcon()
{
return (HCURSOR) m_hIcon;
}void CTestDlg::OnButton1()
{
pause = 1;
if(WaitForSingleObject(hEvent, INFINITE) == WAIT_OBJECT_0)
{
a = 2;
}
pause = 0;
}
HANDLE hEvent = NULL;
int pause =0;
void adddata();
BOOL bTrun = true;
int a =0;
void ListenerProcess(LPVOID lpParameter) //用于监听文件夹中是否有新文件需要更新
{
while(bTrun)
{
if( pause == 0)
{
if(WaitForSingleObject(hEvent, INFINITE) == WAIT_OBJECT_0)
{
a = 1;
}
adddata();
}
}
ExitThread(0);
}void adddata()
{
ResetEvent(hEvent);
if(a == 2)
{
::MessageBox(NULL,"进入了","进入了",MB_OK);
}
SetEvent(hEvent);
}
class CAboutDlg : public CDialog
{
public:
CAboutDlg();// Dialog Data
//{{AFX_DATA(CAboutDlg)
enum { IDD = IDD_ABOUTBOX };
//}}AFX_DATA // ClassWizard generated virtual function overrides
//{{AFX_VIRTUAL(CAboutDlg)
protected:
virtual void DoDataExchange(CDataExchange* pDX); // DDX/DDV support
//}}AFX_VIRTUAL// Implementation
protected:
//{{AFX_MSG(CAboutDlg)
//}}AFX_MSG
DECLARE_MESSAGE_MAP()
};CAboutDlg::CAboutDlg() : CDialog(CAboutDlg::IDD)
{
//{{AFX_DATA_INIT(CAboutDlg)
//}}AFX_DATA_INIT
}void CAboutDlg::DoDataExchange(CDataExchange* pDX)
{
CDialog::DoDataExchange(pDX);
//{{AFX_DATA_MAP(CAboutDlg)
//}}AFX_DATA_MAP
}BEGIN_MESSAGE_MAP(CAboutDlg, CDialog)
//{{AFX_MSG_MAP(CAboutDlg)
// No message handlers
//}}AFX_MSG_MAP
END_MESSAGE_MAP()/////////////////////////////////////////////////////////////////////////////
// CTestDlg dialogCTestDlg::CTestDlg(CWnd* pParent /*=NULL*/)
: CDialog(CTestDlg::IDD, pParent)
{
//{{AFX_DATA_INIT(CTestDlg)
// NOTE: the ClassWizard will add member initialization here
//}}AFX_DATA_INIT
// Note that LoadIcon does not require a subsequent DestroyIcon in Win32
m_hIcon = AfxGetApp()->LoadIcon(IDR_MAINFRAME);
}void CTestDlg::DoDataExchange(CDataExchange* pDX)
{
CDialog::DoDataExchange(pDX);
//{{AFX_DATA_MAP(CTestDlg)
// NOTE: the ClassWizard will add DDX and DDV calls here
//}}AFX_DATA_MAP
}BEGIN_MESSAGE_MAP(CTestDlg, CDialog)
//{{AFX_MSG_MAP(CTestDlg)
ON_WM_SYSCOMMAND()
ON_WM_PAINT()
ON_WM_QUERYDRAGICON()
ON_BN_CLICKED(IDC_BUTTON1, OnButton1)
//}}AFX_MSG_MAP
END_MESSAGE_MAP()/////////////////////////////////////////////////////////////////////////////
// CTestDlg message handlersBOOL CTestDlg::OnInitDialog()
{
CDialog::OnInitDialog(); // Add "About..." menu item to system menu. // IDM_ABOUTBOX must be in the system command range.
ASSERT((IDM_ABOUTBOX & 0xFFF0) == IDM_ABOUTBOX);
ASSERT(IDM_ABOUTBOX < 0xF000); CMenu* pSysMenu = GetSystemMenu(FALSE);
if (pSysMenu != NULL)
{
CString strAboutMenu;
strAboutMenu.LoadString(IDS_ABOUTBOX);
if (!strAboutMenu.IsEmpty())
{
pSysMenu->AppendMenu(MF_SEPARATOR);
pSysMenu->AppendMenu(MF_STRING, IDM_ABOUTBOX, strAboutMenu);
}
} // Set the icon for this dialog. The framework does this automatically
// when the application's main window is not a dialog
SetIcon(m_hIcon, TRUE); // Set big icon
SetIcon(m_hIcon, FALSE); // Set small icon
pThread = AfxBeginThread( (AFX_THREADPROC)ListenerProcess,
NULL,
THREAD_PRIORITY_NORMAL,
0,
0,
NULL);
hEvent = CreateEvent(NULL,TRUE,TRUE,NULL);
// TODO: Add extra initialization here
return TRUE; // return TRUE unless you set the focus to a control
}void CTestDlg::OnSysCommand(UINT nID, LPARAM lParam)
{
if ((nID & 0xFFF0) == IDM_ABOUTBOX)
{
CAboutDlg dlgAbout;
dlgAbout.DoModal();
}
else
{
CDialog::OnSysCommand(nID, lParam);
}
}// If you add a minimize button to your dialog, you will need the code below
// to draw the icon. For MFC applications using the document/view model,
// this is automatically done for you by the framework.void CTestDlg::OnPaint()
{
if (IsIconic())
{
CPaintDC dc(this); // device context for painting SendMessage(WM_ICONERASEBKGND, (WPARAM) dc.GetSafeHdc(), 0); // Center icon in client rectangle
int cxIcon = GetSystemMetrics(SM_CXICON);
int cyIcon = GetSystemMetrics(SM_CYICON);
CRect rect;
GetClientRect(&rect);
int x = (rect.Width() - cxIcon + 1) / 2;
int y = (rect.Height() - cyIcon + 1) / 2; // Draw the icon
dc.DrawIcon(x, y, m_hIcon);
}
else
{
CDialog::OnPaint();
}
}// The system calls this to obtain the cursor to display while the user drags
// the minimized window.
HCURSOR CTestDlg::OnQueryDragIcon()
{
return (HCURSOR) m_hIcon;
}void CTestDlg::OnButton1()
{
pause = 1;
if(WaitForSingleObject(hEvent, INFINITE) == WAIT_OBJECT_0)
{
a = 2;
}
pause = 0;
}
{
a=2;
} 当点下函数时,没有修改事件信号状态!再看 ListenerProcess 函数 void ListenerProcess(LPVOID lpParameter) //用于监听文件夹中是否有新文件需要更新
{
while(bTrun)
{ // 由于时间信号没修改,虽然a变成2,但是会马上通过下面if语句将a改回 1 if(WaitForSingleObject(hEvent, INFINITE) == WAIT_OBJECT_0)
{
a = 1; } adddata(); // 由于 a 被改回 1 ,这里当然是老样子
}
ExitThread(0);
}
// 点击按钮
void CTest4Dlg::OnBnClickedButton2()
{
// TODO: 在此添加控件通知处理程序代码 if(WaitForSingleObject(hEvent, INFINITE) == WAIT_OBJECT_0)
{
ResetEvent(hEvent); // 将线程暂停在 waitForSingleObjectEvent 语句
a=2;
// 把 adddata()的事情放到这里
::MessageBox(NULL,L"进入了",L"进入了",MB_OK);
SetEvent(hEvent); // 恢复线程
}
}同时 在 线程里 去掉 adddata()函数