1. 步骤1(打开First Activity):经过onCreate、onStart、onResume后First Activity就展现啦;
2. 步骤2(跳转至Second Activity):首先First Activity暂停(onPause),接下来Second Activity展现(onCreate、onStart、onResume),最后First Activity停止(onStop);
3. 步骤3(返回到First Activity):首先Second Activity暂停(onPause),接下来First Activity重新打开并展现(onRestart、onStart、onResume),最后Second Activity停止并销毁(onStop、onDestroy);
4. 步骤4(退出First Activity):经过onPause、onStop、onDestroy后First Activity暂停、停止并最终销毁。