这里主要指import的修改，Android Studio自动帮助项目升级成androidx时，很多控件的路径在androidx中都变更了，所以需要全局搜索一键替换。
全局替换: Edit -> Find -> Replace in path
列举了一些常用的：
| 修改前android.support | 修改后androidx |
|---|---|
| import androidx.appcompat.widget.RecyclerView; | import androidx.recyclerview.widget.RecyclerView; |
| import androidx.core.view.ViewPager; | import androidx.viewpager.widget.ViewPager; |
| import androidx.core.view.PagerAdapter; | import androidx.viewpager.widget.PagerAdapter; |
| import androidx.core.app.Fragment; | import androidx.fragment.app.Fragment; |
| import androidx.core.app.FragmentManager; | import androidx.fragment.app.FragmentManager; |
| import androidx.core.app.FragmentTransaction; | import androidx.fragment.app.FragmentTransaction; |
| import androidx.core.content.LocalBroadcastManager; | import androidx.localbroadcastmanager.content.LocalBroadcastManager; |
| import androidx.appcompat.widget.DefaultItemAnimator; | import androidx.recyclerview.widget.DefaultItemAnimator; |
| import androidx.appcompat.widget.LinearLayoutManager; | import androidx.recyclerview.widget.LinearLayoutManager; |
| import androidx.appcompat.widget.GridLayoutManager; | import androidx.recyclerview.widget.GridLayoutManager; |
| import androidx.appcompat.widget.StaggeredGridLayoutManager; | import androidx.recyclerview.widget.StaggeredGridLayoutManager; |
| import android.support.design.widget.CoordinatorLayout; | import androidx.coordinatorlayout.widget.CoordinatorLayout; |
| import android.support.design.widget.CoordinatorLayout; | import androidx.coordinatorlayout.widget.CoordinatorLayout; |
| import android.support.design.widget.TabLayout; | import com.google.android.material.tabs.TabLayout; |
| import android.support.design.widget.AppBarLayout; | import com.google.android.material.appbar.AppBarLayout |
