activity
isn't a defined symbol, but . In this case, since the code is in an activity, use the current object:
pptViewer.loadPPT(this, "/home/waheed/lab6.pptx");
You probably copy-pasted from the readme, as the activity
used as sample method input in the readme means you have to pass an activity instance. You don't declare Activity activity = ...
, but since you're in an activity you can use this
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