迁移到 AndroidX

AndroidX 将原始支持库 API 替换为 androidx 命名空间中的软件包。只有软件包和 Maven 工件名称发生了变化；类名、方法名和字段名没有变化。

注意：我们建议在单独的分支中执行迁移。此外，还应设法避免在执行迁移时重构代码。

前提条件

执行迁移之前，请先将应用更新到最新版本。 我们建议您将项目更新为使用支持库的最终版本：版本 28.0.0。 这是因为，1.0.0 版本的 AndroidX 工件是与支持库 28.0.0 工件等效的二进制文件。

使用 Android Studio 迁移现有项目

使用 Android Studio 3.2 及更高版本，您只需从菜单栏中依次选择 Refactor > Migrate to AndroidX，即可将现有项目迁移到 AndroidX。

重构命令使用两个标记。默认情况下，这两个标记在 [gradle.properties]
(https://developer.android.google.cn/studio/build#properties-files) 文件中都设为 true：
android.useAndroidX=true
Android 插件会使用对应的 AndroidX 库而非支持库。
android.enableJetifier=true

Android 插件会通过重写现有第三方库的二进制文件，自动将这些库迁移为使用 AndroidX。

注意：内置的 Android Studio 迁移功能可能并不能完成所有操作。根据您的构建配置，您可能需要手动更新构建脚本和 Proguard 映射。例如，如果您在一个单独的构建文件中维护依赖项配置，请使用下述映射文件来检查依赖项并将其更新为对应的 AndroidX 软件包。

以下是前者是support库，即支持库的中的类映射，后者是对应的androidx下类映射：
（小技巧：在AS中双击shift，输入replace in path ，点击进行全局替换。）

全部替换完成以后，需要注意的是：
（1）清除项目缓存数据：每个module下的build文件夹手动删除；
（2）点击invalidate caches/restart 进行重启AS。

android.support.v4.app.Fragment
androidx.fragment.app.Fragment

android.support.v4.view.ViewPager
androidx.viewpager.widget.ViewPager

android.support.constraint.ConstraintLayout
androidx.constraintlayout.widget.ConstraintLayout

android.support.v4.app.FragmentPagerAdapter
androidx.fragment.app.FragmentPagerAdapter

android.support.v4.app.FragmentStatePagerAdapter
androidx.fragment.app.FragmentStatePagerAdapter

android.support.annotation.DrawableRes
androidx.annotation.DrawableRes

android.support.v4.os.ParcelableCompat
androidx.core.os.ParcelableCompat

android.support.v4.os.ParcelableCompatCreatorCallbacks
androidx.core.os.ParcelableCompatCreatorCallbacks

android.support.v4.view.AccessibilityDelegateCompat
androidx.core.view.AccessibilityDelegateCompat

android.support.v4.view.MotionEventCompat
androidx.core.view.MotionEventCompat

android.support.v4.view.PagerAdapter
androidx.viewpager.widget.PagerAdapter

android.support.v4.view.VelocityTrackerCompat
androidx.core.view.VelocityTrackerCompat

android.support.v4.view.ViewCompat
androidx.core.view.ViewCompat

android.support.v4.view.ViewConfigurationCompat
androidx.core.view.ViewConfigurationCompat

android.support.v4.view.accessibility.AccessibilityEventCompat
androidx.core.view.accessibility.AccessibilityEventCompat

android.support.v4.view.accessibility.AccessibilityNodeInfoCompat
androidx.core.view.accessibility.AccessibilityNodeInfoCompat

android.support.v4.view.accessibility.AccessibilityRecordCompat
androidx.core.view.accessibility.AccessibilityRecordCompat

android.support.v4.widget.EdgeEffectCompat
androidx.core.widget.EdgeEffectCompat

android.support.v4.content.FileProvider
androidx.core.content.FileProvider

android.support.annotation.NonNull
androidx.annotation.NonNull

android.support.annotation.Nullable
androidx.annotation.Nullable

android.databinding.DataBindingUtil
androidx.databinding.DataBindingUtil

android.support.v4.app.AppOpsManagerCompat
androidx.core.app.AppOpsManagerCompat

android.support.annotation.ColorInt
androidx.annotation.ColorInt

android.support.v4.app.ActivityCompat
androidx.core.app.ActivityCompat

android.support.v4.content.ContextCompat
androidx.core.content.ContextCompat

android.support.v7.app.AppCompatActivity
androidx.appcompat.app.AppCompatActivity

android.databinding.BaseObservable
androidx.databinding.BaseObservable

android.support.v4.graphics.drawable.RoundedBitmapDrawable
androidx.core.graphics.drawable.RoundedBitmapDrawable

android.support.v7.widget.AppCompatImageView
androidx.appcompat.widget.AppCompatImageView

android.support.multidex.MultiDexApplication
androidx.multidex.MultiDexApplication

android.support.v7.widget.AppCompatTextView
androidx.appcompat.widget.AppCompatTextView

android.support.annotation.RequiresApi
androidx.annotation.RequiresApi

android.support.v4.content.PermissionChecker
androidx.core.content.PermissionChecker

android.support.v4.view.GestureDetectorCompat
androidx.core.view.GestureDetectorCompat

android.support.v7.widget.RecyclerView
androidx.recyclerview.widget.RecyclerView

android.databinding.Bindable
androidx.databinding.Bindable

android.databinding.ViewDataBinding
androidx.databinding.ViewDataBinding

android.support.v4.app.NotificationCompat
androidx.core.app.NotificationCompat

android.support.v4.content.LocalBroadcastManager
androidx.localbroadcastmanager.content.LocalBroadcastManager

android.support.v4.app.NotificationManagerCompat
androidx.core.app.NotificationManagerCompat

android.support.v4.view.PagerAdapter
androidx.viewpager.widget.PagerAdapter

android.support.v4.view.ViewCompat
androidx.core.view.ViewCompat

android.support.v4.widget.EdgeEffectCompat
androidx.core.widget.EdgeEffectCompat

android.support.v4.view.NestedScrollingParent
androidx.core.view.NestedScrollingParent

android.support.v4.view.MotionEventCompat
androidx.core.view.MotionEventCompat

android.support.v4.widget.NestedScrollView
androidx.core.widget.NestedScrollView

android.support.v7.widget.LinearLayoutManager
androidx.recyclerview.widget.LinearLayoutManager

android.support.v7.widget.StaggeredGridLayoutManager
androidx.recyclerview.widget.StaggeredGridLayoutManager

android.databinding.BindingAdapter
androidx.databinding.BindingAdapter

android.support.v4.widget.ScrollerCompat
androidx.core.widget.ScrollerCompat

android.support.v4.widget.SwipeRefreshLayout
androidx.swiperefreshlayout.widget.SwipeRefreshLayout

android.support.v4.view.animation.FastOutLinearInInterpolator
androidx.interpolator.view.animation.FastOutLinearInInterpolator

android.support.v4.view.animation.FastOutSlowInInterpolator
androidx.interpolator.view.animation.FastOutSlowInInterpolator

android.support.v4.view.animation.LinearOutSlowInInterpolator
androidx.interpolator.view.animation.LinearOutSlowInInterpolator

android.support.annotation.IntDef
androidx.annotation.IntDef

android.support.annotation.LayoutRes
androidx.annotation.LayoutRes

android.support.annotation.StringRes
androidx.annotation.StringRes

android.support.design.widget.TabLayout
com.google.android.material.tabs.TabLayout

android.support.v4.util.Pools
androidx.core.util.Pools

android.support.v4.view.GravityCompat
androidx.core.view.GravityCompat

android.support.v4.widget.TextViewCompat
androidx.core.widget.TextViewCompat

android.support.v7.app.ActionBar
androidx.appcompat.app.ActionBar

android.support.v4.graphics.ColorUtils
androidx.core.graphics.ColorUtils

android.support.v7.widget.OrientationHelper
androidx.recyclerview.widget.OrientationHelper

// UDesk
android.support.v4.text.TextUtilsCompat
androidx.core.text.TextUtilsCompat

android.support.v4.app.LoaderManager
androidx.loader.app.LoaderManager

android.support.v4.content.CursorLoader
androidx.loader.content.CursorLoader

android.support.v4.content.Loader
androidx.loader.content.Loader

android.support.annotation.CheckResult
androidx.annotation.CheckResult

android.arch.lifecycle.MutableLiveData
androidx.lifecycle.MutableLiveData

android.arch.lifecycle.LiveData

android.arch.lifecycle.Observer

android.arch.lifecycle.ViewModelProviders
androidx.lifecycle.ViewModelProviders

android.support.v7.widget.DefaultItemAnimator
androidx.recyclerview.widget.DefaultItemAnimator

android.support.v7.widget.GridLayoutManager
androidx.recyclerview.widget.GridLayoutManager

android.support.v7.widget.AppCompatButton
androidx.appcompat.widget.AppCompatButton

android.support.v7.widget.SimpleItemAnimator
androidx.recyclerview.widget.SimpleItemAnimator

android.support.v7.widget.PagerSnapHelper
androidx.recyclerview.widget.PagerSnapHelper

android.support.design.widget.AppBarLayout
com.google.android.material.appbar.AppBarLayout
android.support.design.widget.CoordinatorLayout
androidx.coordinatorlayout.widget.CoordinatorLayout

android.support.v7.widget.Toolbar
androidx.appcompat.widget.Toolbar

android.support.design.widget.CollapsingToolbarLayout
com.google.android.material.appbar.CollapsingToolbarLayout

android.support.v7.widget.CardView
androidx.cardview.widget.CardView

android.support.annotation.FloatRange
androidx.annotation.FloatRange

android.support.v7.widget.helper.ItemTouchHelper
androidx.recyclerview.widget.ItemTouchHelper

android.support.v7.widget.AppCompatSeekBar
androidx.appcompat.widget.AppCompatSeekBar

android.support.v7.widget.AppCompatEditText
androidx.appcompat.widget.AppCompatEditText

android.support.design.widget.FloatingActionButton
com.google.android.material.floatingactionbutton.FloatingActionButton

android.support.annotation.AnyThread
androidx.annotation.AnyThread

（已同步CSDN：https://blog.csdn.net/u010231454/article/details/113865022）
（已同步掘金：https://juejin.cn/post/6930877189747376136/）