Some　urgent　shortcomings　in　previous　derivations　of　geodesic　equations　are　remedied　in　this　paper.　In　contrast　to　the　unnatural　and　awkward　treatment　in　previous　works,　here　we　derive　the　geodesic　equations　of　massive　and　massless　particles　in　a　unified　and　self-consistent　manner.　Furthermore,　we　extend　to　investigate　the　Hawking　radiation　via　tunneling　from　charged　black　holes　in　the　context　of　AdS　spacetime.　Of　special　interest,　the　application　of　the　first　law　of　black　hole　thermodynamics　in　tunneling　integration　manifestly　simplifies　the　calculation.