带线程的多个对话框中的进度条

Question

My application has to keep track of time and alert user at different stages to allow or not allow certain actions. Because the user will be waiting, I want to show a progress to show wait time. For example my device has to wait for 5 minutes when it is started before it can be ready to use. The problem is that user can navigate to multiple dialogs and I want to show the progress bar on 2 of these dialogs. I used a thread to 'run the clock' and it will post messages to the GUI when progress bar needs to be updated or time activity is complete.

The problem is that I can pass the handle of the initial window which can receive notifications from the thread but what happens when user go to the other screen? This other window don't even exist yet. Is there any other mechanism I can use? My goal is to to reuse the time-check code in both the dialogs.

A very simplified code is below:

UINT MonitorTimeThread(LPVOID pVoid )
{
    HWND hWnd = ( HWND ) pVoid;

    HANDLE timer = ::CreateWaitableTimer(NULL, FALSE, NULL);

    SYSTEMTIME t;
    ::GetSystemTime(&t);

    LARGE_INTEGER alarm;
    ::SystemTimeToFileTime(&t, (FILETIME *)&alarm);
    ::SetWaitableTimer(timer, &alarm, 5000, NULL, NULL, FALSE);

    bool done = false;

    while (!done )
    {

        if (WaitForSingleObject( timer, INFINITE ) == WAIT_OBJECT_0 )
        {
            TRACE("time inteval has passed\r\n");

            // update the progress bar on GUI
            PostThreadMessage(hWnd, UM_PROGRESS_TICK, 0 );

            // if user has switch to another window, how to direct messages to that?
        }
    }

    return 0;
}

Answer 1

I'm not sure if I'm a victim of the " If all you have is a hammer everything looks like a nail " syndrome but you may use a similar solution to https://stackoverflow.com/a/17033971/145757

class MyTwoWindows
{
    public: HWND window1;
    public: HWND window2;

    public: MyTwoWindows(HWND w1, HWND w2)
    {
        this->window1 = w1;
        this->window2 = w2;
    }
};

Then I don't know how you transmit the data to the MonitorTimeThread function but instead of a single HWND you could pass an instance of MyTwoWindows .

UINT MonitorTimeThread(LPVOID pVoid )
{
    MyTwoWindows* data = (MyTwoWindows*) pVoid;
    ...
    PostThreadMessage(data->window1, UM_PROGRESS_TICK, 0 );
    PostThreadMessage(data->window2, UM_PROGRESS_TICK, 0 );

Moreover if the two windows are not created at the same time you can still modify the object live:

void CreateSecondWindow()
{
    HWND hwnd = // a new window;
    myTwoWindows->window2 = hwnd;
}

And in the monitoring function:

if (data->window2 != NULL)
{
    PostThreadMessage(data->window2, UM_PROGRESS_TICK, 0 );
}

Sorry if this is irrelevant but it's late. :)

PS: I've written about this syndrome here: http://pragmateek.com/if-all-you-have-is-a-hammer/ (implemented in C# but good for C++ programmers too) ;)