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這是msdn的metro相機應用程序。此代碼用於顯示來自攝像機的預覽。攝像機列表將顯示在組合框中。用戶可以選擇攝像機以查看所選攝像機的預覽，但是當我更換攝像機時，它首先釋放資源，然後啓動由於發佈過程是異步過程，並且在後臺運行，所以在發佈之前，它會啓動所選攝像機的預覽，同時釋放刪除「m_MediaCaptureMgr」指針和程序崩潰。在Windows 8 metro應用程序中同步兩個ppl任務
在Win 32中，我可以使用waitforSingle對象來同步它。我想知道如何最好地在WinRT和ppl任務中同步。
void CameraApp::MainPage::cmbCameraSelector_SelectionChanged(Platform::Object^ sender, Windows::UI::Xaml::Controls::SelectionChangedEventArgs^ e)
{
if(m_DeviceVector.size() > 0)
{
m_CaptureInitSettings->VideoDeviceId = m_DeviceVector[cmbCameraSelector->SelectedIndex]->Id;
InitMediaCapture();
}
}
void CameraApp::MainPage::InitMediaCapture()
{
ReleaseMediaCapture();
//Sleep(3000);
auto _this = this;
m_MediaCaptureMgr = ref new MediaCapture();
task<void> stratPreview(m_MediaCaptureMgr->InitializeAsync(m_CaptureInitSettings));
stratPreview.then([_this]
{
_this->previewElement->Source = _this->m_MediaCaptureMgr;
task<void> startPrev(_this->m_MediaCaptureMgr->StartPreviewAsync());
startPrev.then([=]
{
return _this->GetCameraSettings();
});
});
}
void CameraApp::MainPage::ReleaseMediaCapture()
{
if (m_MediaCaptureMgr)
{
auto prevOp = m_MediaCaptureMgr->StopPreviewAsync();
task<void> releaseMediaCapture(m_MediaCaptureMgr->StopPreviewAsync());
releaseMediaCapture.then([=]
{
m_MediaCaptureMgr = nullptr;
bRelease = false;
});
}
}