我是 WinRT c++ 的新手。我正在尝试从 C# 传递 StorageFile 图像并打开文件并将其设置为 WinRT 中 BitmapImage 中的源以提取图像的高度和宽度。我正在使用以下代码。
auto openOperation = StorageImageFile->OpenAsync(FileAccessMode::Read); // from http://msdn.microsoft.com/en-us/library/windows/desktop/hh780393%28v=vs.85%29.aspx
openOperation->Completed = ref new
AsyncOperationCompletedHandler<IRandomAccessStream^>(
[=](IAsyncOperation<IRandomAccessStream^> ^operation, AsyncStatus status)
{
auto Imagestream = operation->GetResults();
BitmapImage^ bmp = ref new BitmapImage();
auto bmpOp = bmp->SetSourceAsync(Imagestream);
bmpOp->Completed = ref new
AsyncActionCompletedHandler (
[=](IAsyncAction^ action, AsyncStatus status)
{
action->GetResults();
UINT32 imageWidth = (UINT32)bmp->PixelWidth;
UINT32 imageHeight = (UINT32)bmp->PixelHeight;
});
});
这段代码似乎不起作用。在行 BitmapImage^ bmp = ref new BitmapImage(); 之后调试器停止说没有找到源代码。 你能帮我写出正确的代码吗？
最佳答案
我想你打算写 openOperation->Completed += ref new... 和 bmpOp->Completed += ref new....我不是 C++ 专家，但据我所知，异步操作通常包含在 create_task 调用中。不太确定为什么 - 也许是为了避免在不取消订阅的情况下订阅事件？
我觉得大概应该是这样的:
auto bmp = ref new BitmapImage();
create_task(storageImageFile->OpenAsync(FileAccessMode::Read)) // get the stream
.then([bmp](IRandomAccessStream^ ^stream) // continuation lambda
{
return create_task(bmp->SetSourceAsync(stream)); // needs to run on ASTA/Dispatcher thread
}, task_continuation_context::use_current()) // run on ASTA/Dispatcher thread
.then([bmp]() // continuation lambda
{
UINT32 imageWidth = (UINT32)bmp->PixelWidth; // needs to run on ASTA/Dispatcher thread
UINT32 imageHeight = (UINT32)bmp->PixelHeight; // needs to run on ASTA/Dispatcher thread
// TODO: use imageWidth and imageHeight
}, task_continuation_context::use_current()); // run on ASTA/Dispatcher thread
关于c++ - WinRT c++ 中的 BitmapImage SetSourceAsync，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/25932162/