How to exit the underway progress?

A progress costs a lot of time,how to exit it.

Can I use some dialog like the window in the image to Stop the underway progress?

There is nothing in the API. You either need to write a Ruby C/C++ extension and create your own native threaded dialog, or you would need to slice your operation in parts and use a timer (UI.start_timer) - though the latter will make total running time slower.

Having said that, if you want to import a SKP into the model there is a way to do display progress: Homepage | SketchUp Developer

Thanks you thomthom! The UI.messagebox cannot be a thread,right?

I found UI.messagebox will blocking the whole progress so that others have to wait.when you press the button,blocking will be ended.