Android Screen Resolution

the problem am having is the different Android Device Screen size. when i lunch my project on to my phone it works perfect because i build it and test it on my phone, but when i lunch it to my Android tablet it does not fit the screen perfect has it did on my phone, i would love to know how to build one project to fit all android Device screen. if your guys can help me in anyway to fix this problem and apply it to my project i would appreciate it thank you.