cancel

Cancels a pending payment, if one exists and can be canceled. In this case, the method returns CancelResult.CANCELED and the payment callbacks will be called with PaymentErrorCode.CANCELED to indicate the cancellation.

Otherwise, this method will return CancelResult.NO_PAYMENT_IN_PROGRESS if there is no payment to be canceled, or CancelResult.NOT_CANCELABLE if there is a payment but it cannot be canceled.