file - UWP : Catch error when reading file

Question

我已经能够使用以下代码在UWP C++应用程序中成功打开和读取文件:

FileOpenPicker^ openPicker = ref new FileOpenPicker();
openPicker->SuggestedStartLocation= PickerLocationId::DocumentsLibrary;
openPicker->FileTypeFilter->Append(".txt");


create_task(openPicker->PickSingleFileAsync()).then([this](StorageFile^ file)
{
    if (file)
    {
        create_task(FileIO::ReadTextAsync(file)).then([this](Platform::String^ text) {

            MessageDialog^ msg = ref new MessageDialog(text);
            msg->ShowAsync();

        });
    }
    else
    {
        MessageDialog^ msg = ref new MessageDialog("Operation cancelled.");
        msg->ShowAsync();
    }
});

但是，如果文件内容是非文本的，例如二进制文件，应用程序崩溃。如何实现错误处理？我尝试使用 try...catch失败。

Answer 1

我设法通过解决问题

https://social.msdn.microsoft.com/Forums/en-US/5b84396b-f071-4c29-ab11-78757d0206f1/uwp-try-catch-block-doesnt-work-in-my-uwp?forum=wpdevelop

Exception handling, WinRT C++ concurrency async tasks

try...catch应该放在异步任务中。我把它放在外面。为此，应更改 create_task()的参数:

FileOpenPicker^ openPicker = ref new FileOpenPicker();
openPicker->SuggestedStartLocation= PickerLocationId::DocumentsLibrary;
openPicker->FileTypeFilter->Append(".txt");


create_task(openPicker->PickSingleFileAsync()).then([this](StorageFile^ file)
{
    if (file)
    {
            create_task(FileIO::ReadTextAsync(file)).then([this](task<String^> currentTask) {

                try {
                    String ^text = currentTask.get();
                    MessageDialog^ msg = ref new MessageDialog(text);
                    msg->ShowAsync();
                }
                catch (...) {
                    MessageDialog^ msg = ref new MessageDialog("Exception handled.");
                    msg->ShowAsync();
                }
            });

    }
    else
    {
        MessageDialog^ msg = ref new MessageDialog("Operation cancelled.");
        msg->ShowAsync();
    }
});

当此代码在Visual Studio中运行时，发生错误时，它仍会断断续续地显示一些十六进制符号。只需单击 Continue或 F5即可获得 Exception handled.错误消息。