android系统三大核心:AmS/WmS/View;
View:measure/layout/draw;剪切clip区域,子View绘制起始点都是00;measure是处理fill_parent/match_content/match_parent属性;
WmS:侧重窗口对象的管理;token负责通讯;
AmS:侧重Activity的管理;TaskRecord/ActivityRecord/ProcessRecord;任何activity的启动/关闭都必须通过AmS;A启动B/按Back返回到B/长安Home返回;启动优先,空闲时执行onStop函数;