Why can't I see the view on the screen or click "no response" after adding a view?

Invisible after adding a view:

1. The created view is not added to the parent view.

2. No background color is set for the view. The color is clearcolor.

3. No frame is set when a view is created.

4. The process of creating a view is written in the method, but it is not called

5. The parent view to be added is nil, and the parent view does not exist. Therefore, the parent view cannot be added.

Cannot respond to interaction after adding a view

1. Find the hierarchical relationship of the view, whether there are other views above the current view, and set the color to clearcolor

2. The view is out of the management scope of the parent view and cannot respond to interaction when the view is out of the management scope of the parent view.

3. View user interaction (userinteractionenabled) may not be enabled or accidentally disabled

4. the user interaction of the parent view is disabled, so manually open the user interaction of the view to be used.

Why can't I see the view on the screen or click "no response" after adding a view?