I want to finish the activity from an other activity on pressing the back button

I want to finish the activity from an other activity on pressing the back
button

I have an activity named QRCodeReader it has a back button on it. It scans
the qr code and pass the id to MetaioCloudARViewTestActivity to start the
channel. Its working fine. But when i press the back button of the
qrCodeReader it finishes the current activity but it loads the blank arel
camera web view of MetaioCloudARViewTestActivity. So i want to finish that
the web view also. If i use the finish in onResume of
MetaioCloudARViewTestActivity it works fine for back button of
QRCodeReader. But i need that activity when i have to scan the code. I
just want to finish it on pressing the back button in QRCodeReader.