问题
I opened Landmark App using SwiftUI on Xcode 11 in macOS Catalina(10.15) and while opening the Canvas Editor for .swift files containing SwiftUI is showing
Cannot preview in this file - active scheme does not build this file
Try Again, Diagonistics option or restarting Xcode not solving the problem.
回答1:
Select the Scheme that has the current file to Preview
回答2:
If this is a new project coming from a copied folder and inside an iCloud folder, just close Xcode and relaunch it. The sync was not yet done.
回答3:
I experienced the same issue. All I did was to copy the "StartingPoint" folder out of the downloaded folder and relaunched the project. It worked!!!
回答4:
I encountered the same error for some of my SwiftUI View files when trying to preview on Canvas. What fixed the issue was I copied the code within the current file, deleted the file, created a new SwiftUI View file under the same name and pasted the original code. Hope that helps!
Creating a new folder in Documents/Desktop and copying the files over also resolves the issue.
回答5:
In the schemes I was able to select, it contained only one scheme. Reopening the folder in a folder that's not in the Downloads directory made live editing work for me
来源：https://stackoverflow.com/questions/58416469/cannot-preview-in-this-file-active-scheme-does-not-build-this-file-swiftui-o