第一次启动: oncreate onstart onresume
按下home或电源键 onPause onSaveInstance, onstop
按下back键 onpause, onstop
ActivityA 启动ActivityB ActivityA: onPause ---> ActivityB oncreate-->onstart--onResume ----> ActivityA onsaveInstance
onNewIntent如果被调用,会在onResume之前
第一次启动: oncreate onstart onresume
按下home或电源键 onPause onSaveInstance, onstop
按下back键 onpause, onstop
ActivityA 启动ActivityB ActivityA: onPause ---> ActivityB oncreate-->onstart--onResume ----> ActivityA onsaveInstance
onNewIntent如果被调用,会在onResume之前