The purpose of this study is to evaluate the safety and efficacy of tenofovir alafenamide (TAF) compared to that of tenofovir disoproxil fumarate (TDF) in treatment naive and experienced adult subjects with chronic hepatitis B virus (HBV) infection, as determined by the achievement of HBV DNA less than 29 IU/mL at Week 48 infection, .To compare the efficacy of TAF 25 mg QD versus TDF 300 mg QD for the treatment of HBeAg-negative, chronic hepatitis B in regard to the proportion of subjects with plasma HBV DNA levels below 29 IU/mL at Weeks 96 and 144. To compare the biochemical (ALT normalization) response of TAF 25 mg QD versus TDF 300 mg QD for the treatment of HBeAg-negative, chronic hepatitis B at Weeks 48, 96, and 144.To compare the serological response (loss of HBsAg with seroconversion to anti-HBs) of TAF 25 mg QD versus TDF 300 mg QD for the treatment of HBeAg-negative, chronic hepatitis B at Weeks 48, 96, and 144.The duration of double-blind treatment is 144 weeks (96 weeks under Amendments 1 and 2). At Week 144, all subjects remaining on blinded treatment will be switched to the open-label TAF 25 mg QD extension period for up to an additional 240 weeks (Week 144 throughWeek 384/ED). Subjects already assigned to open-label TAF 25 mg QD at Week 96 per Amendment 1 or 2 will continue on open-label TAF 25 mg QD through Week 384/ED. All subjects who complete the double-blind period of treatment are eligible for participation in the open-label TAF 25 mg QD extension period. Subjects who permanently discontinue study drug(either prematurely [ED] or at the end of study [Week 384]) for reasons other than HBsAg loss with confirmed seroconversion to anti-HBs, will be followed every 4 weeks for 24 weeks off treatment or until initiation of alternative, commercially available HBV therapy, whichever occurs first.