Android : How can I get screen of phone

I am developing an application to share the screen.

Whenever there is a change in the screen

capture the screen.

transfer the photos to the server

You can see the phone is receiving a transmission photo sharing app.

(You can view the incoming phone transfer pictures to share.)

I do not know how to capture the screen.

How can I get screen of phone? Please, Help me.

I've do not understand the following sources

(Android: Screen capturing without root) (Screen Capture in android)

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