Android AndroidX的迁移
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、方法和字段名称没有变化。
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 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。
andorid studio一键替换androidx
如图所示可以完全替换代码中所有文件
工件映射
下表列出了从旧支持库工件到 androidx 的最新映射。您也可以下载包含这些映射信息的 CSV 格式文件。
| 旧构建工件 | AndroidX 构建工件 |
|---|---|
| android.arch.core:common | androidx.arch.core:core-common |
| android.arch.core:core | androidx.arch.core:core |
| android.arch.core:core-testing | androidx.arch.core:core-testing |
| android.arch.core:runtime | androidx.arch.core:core-runtime |
| android.arch.lifecycle:common | androidx.lifecycle:lifecycle-common |
| android.arch.lifecycle:common-java8 | androidx.lifecycle:lifecycle-common-java8 |
| android.arch.lifecycle:compiler | androidx.lifecycle:lifecycle-compiler |
| android.arch.lifecycle:extensions | androidx.lifecycle:lifecycle-extensions |
| android.arch.lifecycle:livedata | androidx.lifecycle:lifecycle-livedata |
| android.arch.lifecycle:livedata-core | androidx.lifecycle:lifecycle-livedata-core |
| android.arch.lifecycle:reactivestreams | androidx.lifecycle:lifecycle-reactivestreams |
| android.arch.lifecycle:runtime | androidx.lifecycle:lifecycle-runtime |
| android.arch.lifecycle:viewmodel | androidx.lifecycle:lifecycle-viewmodel |
| android.arch.paging:common | androidx.paging:paging-common |
| android.arch.paging:runtime | androidx.paging:paging-runtime |
| android.arch.paging:rxjava2 | androidx.paging:paging-rxjava2 |
| android.arch.persistence.room:common | androidx.room:room-common |
| android.arch.persistence.room:compiler | androidx.room:room-compiler |
| android.arch.persistence.room:guava | androidx.room:room-guava |
| android.arch.persistence.room:migration | androidx.room:room-migration |
| android.arch.persistence.room:runtime | androidx.room:room-runtime |
| android.arch.persistence.room:rxjava2 | androidx.room:room-rxjava2 |
| android.arch.persistence.room:testing | androidx.room:room-testing |
| android.arch.persistence:db | androidx.sqlite:sqlite |
| android.arch.persistence:db-framework | androidx.sqlite:sqlite-framework |
| com.android.support.constraint:constraint-layout | androidx.constraintlayout:constraintlayout |
| com.android.support.constraint:constraint-layout-solver | androidx.constraintlayout:constraintlayout-solver |
| com.android.support.test.espresso.idling:idling-concurrent | androidx.test.espresso.idling:idling-concurrent |
| com.android.support.test.espresso.idling:idling-net | androidx.test.espresso.idling:idling-net |
| com.android.support.test.espresso:espresso-accessibility | androidx.test.espresso:espresso-accessibility |
| com.android.support.test.espresso:espresso-contrib | androidx.test.espresso:espresso-contrib |
| com.android.support.test.espresso:espresso-core | androidx.test.espresso:espresso-core |
| com.android.support.test.espresso:espresso-idling-resource | androidx.test.espresso:espresso-idling-resource |
| com.android.support.test.espresso:espresso-intents | androidx.test.espresso:espresso-intents |
| com.android.support.test.espresso:espresso-remote | androidx.test.espresso:espresso-remote |
| com.android.support.test.espresso:espresso-web | androidx.test.espresso:espresso-web |
| com.android.support.test.janktesthelper:janktesthelper | androidx.test.jank:janktesthelper |
| com.android.support.test.services:test-services | androidx.test:test-services |
| com.android.support.test.uiautomator:uiautomator | androidx.test.uiautomator:uiautomator |
| com.android.support.test:monitor | androidx.test:monitor |
| com.android.support.test:orchestrator | androidx.test:orchestrator |
| com.android.support.test:rules | androidx.test:rules |
| com.android.support.test:runner | androidx.test:runner |
| com.android.support:animated-vector-drawable | androidx.vectordrawable:vectordrawable-animated |
| com.android.support:appcompat-v7 | androidx.appcompat:appcompat |
| com.android.support:asynclayoutinflater | androidx.asynclayoutinflater:asynclayoutinflater |
| com.android.support:car | androidx.car:car-alpha5 |
| com.android.support:cardview-v7 | androidx.cardview:cardview |
| com.android.support:collections | androidx.collection:collection |
| com.android.support:coordinatorlayout | androidx.coordinatorlayout:coordinatorlayout |
| com.android.support:cursoradapter | androidx.cursoradapter:cursoradapter |
| com.android.support:customtabs | androidx.browser:browser |
| com.android.support:customview | androidx.customview:customview |
| com.android.support:design | com.google.android.material:material-rc01 |
| com.android.support:documentfile | androidx.documentfile:documentfile |
| com.android.support:drawerlayout | androidx.drawerlayout:drawerlayout |
| com.android.support:exifinterface | androidx.exifinterface:exifinterface |
| com.android.support:gridlayout-v7 | androidx.gridlayout:gridlayout |
| com.android.support:heifwriter | androidx.heifwriter:heifwriter |
| com.android.support:interpolator | androidx.interpolator:interpolator |
| com.android.support:leanback-v17 | androidx.leanback:leanback |
| com.android.support:loader | androidx.loader:loader |
| com.android.support:localbroadcastmanager | androidx.localbroadcastmanager:localbroadcastmanager |
| com.android.support:media2 | androidx.media2:media2-alpha03 |
| com.android.support:media2-exoplayer | androidx.media2:media2-exoplayer-alpha01 |
| com.android.support:mediarouter-v7 | androidx.mediarouter:mediarouter |
| com.android.support:multidex | androidx.multidex:multidex |
| com.android.support:multidex-instrumentation | androidx.multidex:multidex-instrumentation |
| com.android.support:palette-v7 | androidx.palette:palette |
| com.android.support:percent | androidx.percentlayout:percentlayout |
| com.android.support:preference-leanback-v17 | androidx.leanback:leanback-preference |
| com.android.support:preference-v14 | androidx.legacy:legacy-preference-v14 |
| com.android.support:preference-v7 | androidx.preference:preference |
| com.android.support:print | androidx.print:print |
| com.android.support:recommendation | androidx.recommendation:recommendation |
| com.android.support:recyclerview-selection | androidx.recyclerview:recyclerview-selection |
| com.android.support:recyclerview-v7 | androidx.recyclerview:recyclerview |
| com.android.support:slices-builders | androidx.slice:slice-builders |
| com.android.support:slices-core | androidx.slice:slice-core |
| com.android.support:slices-view | androidx.slice:slice-view |
| com.android.support:slidingpanelayout | androidx.slidingpanelayout:slidingpanelayout |
| com.android.support:support-annotations | androidx.annotation:annotation |
| com.android.support:support-compat | androidx.core:core |
| com.android.support:support-content | androidx.contentpager:contentpager |
| com.android.support:support-core-ui | androidx.legacy:legacy-support-core-ui |
| com.android.support:support-core-utils | androidx.legacy:legacy-support-core-utils |
| com.android.support:support-dynamic-animation | androidx.dynamicanimation:dynamicanimation |
| com.android.support:support-emoji | androidx.emoji:emoji |
| com.android.support:support-emoji-appcompat | androidx.emoji:emoji-appcompat |
| com.android.support:support-emoji-bundled | androidx.emoji:emoji-bundled |
| com.android.support:support-fragment | androidx.fragment:fragment |
| com.android.support:support-media-compat | androidx.media:media |
| com.android.support:support-tv-provider | androidx.tvprovider:tvprovider |
| com.android.support:support-v13 | androidx.legacy:legacy-support-v13 |
| com.android.support:support-v4 | androidx.legacy:legacy-support-v4 |
| com.android.support:support-vector-drawable | androidx.vectordrawable:vectordrawable |
| com.android.support:swiperefreshlayout | androidx.swiperefreshlayout:swiperefreshlayout |
| com.android.support:textclassifier | androidx.textclassifier:textclassifier |
| com.android.support:transition | androidx.transition:transition |
| com.android.support:versionedparcelable | androidx.versionedparcelable:versionedparcelable |
| com.android.support:viewpager | androidx.viewpager:viewpager |
| com.android.support:wear | androidx.wear:wear |
| com.android.support:webkit | androidx.webkit:webkit |
总结：
后续很多三方开源框架使用的是androidx如果我们没有替换会有很多兼容问题无法编译通过，为了后续更好维护开发尽早提前替换成androidx