x的最低实验条件

AndroidStudio 3.2.0+
gradle：gradle-4.6以上
本次实验条件：
AndroidStudio 3.3 (AS3.3强制要求最低gradle版本为gradle-4.10-all)
gradle：gradle-4.10-all

使用AndroidX

如果要在新项目中使用AndroidX，则需要将compile SDK设置为Android 9.0（API级别28）或更高版本，并在gradle.properties文件中设置以下两个Android Gradle插件标志。

• android.useAndroidX：设置true为时,Android插件使用相应的AndroidX库而不是支持库。如果未指定,则默认情况下为false标志 。
• android.enableJetifier：设置true为时,Android插件会自动迁移现有的第三方库,通过重写其二进制文件来使用AndroidX。如果未指定，则默认情况下为false标志。

AndroidX概述

AndroidX是Android团队用于在Jetpack中开发，测试，打包，发布和发布库的开源项目 。
AndroidX是对原始Android 支持库的重大改进 。与支持库一样，AndroidX与Android操作系统分开提供，并提供跨Android版本的向后兼容性。AndroidX通过提供功能奇偶校验和新库完全取代了支持库。此外，AndroidX还包括以下功能：

• AndroidX中的所有软件包都以字符串开头，位于一致的命名空间androidx中。支持库包已映射到相应的androidx.*包中。有关所有旧类和构建工件的完整映射到新构件，请参阅“ 包重构”页面。
• 与支持库不同，AndroidX软件包是单独维护和更新的。这些androidx包使用严格的语义版本控制， 从版本1.0.0开始。您可以单独更新项目中的AndroidX库。
• 所有新的支持库开发都将在AndroidX库中进行。这包括维护原始支持库工件和引入新的Jetpack组件。

其实就是对安卓过往v7,v4，design等系列包的一个整合，不用我们多次添加与核对版本号，大大方便了我们的开发，真的是早就该这样做了。

开始体验x

新建工程有个勾，勾上

创建完成后就会发现gradle.properties多了两行

 

这两行的作用主要是自动迁移任何尚未迁移到AndroidX命名空间的Maven依赖项目至AndroidX命名空间，如果是老项目现在想把整个工程其它包替换为androidx包，在手动添加上面这两行后直接使用AS Refactor->Migrate to AndroidX即可。

 

这个时候由于我本地还没有androix这个库,新建工程时的这两个在线引用
implementation 'androidx.appcompat:appcompat:1.0.0-beta01'
implementation 'androidx.constraintlayout:constraintlayout:1.1.2'

也没有引起AS给我自动下载下来androidx整个包，感觉很奇怪，就去官网随便找了一个对应的一个依赖，在线一填，导致它x包所有东西都下载下来了，一切回归正常，在xml和java文件写了好几个以前分布在不同的包的类，没发现什么问题，至此体验结束。
功臣包名：implementation 'com.google.android.material:material:1.0.0-rc01'

旧版本包与AndroidX对照表

旧包	AndroidX
android.arch.core:common	androidx.arch.core:core-common:2.0.0-rc01
android.arch.core:core	androidx.arch.core:core:2.0.0-rc01
android.arch.core:core-testing	androidx.arch.core:core-testing:2.0.0-rc01
android.arch.core:runtime	androidx.arch.core:core-runtime:2.0.0-rc01
android.arch.lifecycle:common	androidx.lifecycle:lifecycle-common:2.0.0-rc01
android.arch.lifecycle:common-java8	androidx.lifecycle:lifecycle-common-java8:2.0.0-rc01
android.arch.lifecycle:compiler	androidx.lifecycle:lifecycle-compiler:2.0.0-rc01
android.arch.lifecycle:extensions	androidx.lifecycle:lifecycle-extensions:2.0.0-rc01
android.arch.lifecycle:livedata	androidx.lifecycle:lifecycle-livedata:2.0.0-rc01
android.arch.lifecycle:livedata-core	androidx.lifecycle:lifecycle-livedata-core:2.0.0-rc01
android.arch.lifecycle:reactivestreams	androidx.lifecycle:lifecycle-reactivestreams:2.0.0-rc01
android.arch.lifecycle:runtime	androidx.lifecycle:lifecycle-runtime:2.0.0-rc01
android.arch.lifecycle:viewmodel	androidx.lifecycle:lifecycle-viewmodel:2.0.0-rc01
android.arch.paging:common	androidx.paging:paging-common:2.0.0-rc01
android.arch.paging:runtime	androidx.paging:paging-runtime:2.0.0-rc01
android.arch.paging:rxjava2	androidx.paging:paging-rxjava2:2.0.0-rc01
android.arch.persistence.room:common	androidx.room:room-common:2.0.0-rc01
android.arch.persistence.room:compiler	androidx.room:room-compiler:2.0.0-rc01
android.arch.persistence.room:guava	androidx.room:room-guava:2.0.0-rc01
android.arch.persistence.room:migration	androidx.room:room-migration:2.0.0-rc01
android.arch.persistence.room:runtime	androidx.room:room-runtime:2.0.0-rc01
android.arch.persistence.room:rxjava2	androidx.room:room-rxjava2:2.0.0-rc01
android.arch.persistence.room:testing	androidx.room:room-testing:2.0.0-rc01
android.arch.persistence:db	androidx.sqlite:sqlite:2.0.0-rc01
android.arch.persistence:db-framework	androidx.sqlite:sqlite-framework:2.0.0-rc01
com.android.support.constraint:constraint-layout	androidx.constraintlayout:constraintlayout:1.1.2
com.android.support.constraint:constraint-layout-solver	androidx.constraintlayout:constraintlayout-solver:1.1.2
com.android.support.test.espresso.idling:idling-concurrent	androidx.test.espresso.idling:idling-concurrent:3.1.0
com.android.support.test.espresso.idling:idling-net	androidx.test.espresso.idling:idling-net:3.1.0
com.android.support.test.espresso:espresso-accessibility	androidx.test.espresso:espresso-accessibility:3.1.0
com.android.support.test.espresso:espresso-contrib	androidx.test.espresso:espresso-contrib:3.1.0
com.android.support.test.espresso:espresso-core	androidx.test.espresso:espresso-core:3.1.0
com.android.support.test.espresso:espresso-idling-resource	androidx.test.espresso:espresso-idling-resource:3.1.0
com.android.support.test.espresso:espresso-intents	androidx.test.espresso:espresso-intents:3.1.0
com.android.support.test.espresso:espresso-remote	androidx.test.espresso:espresso-remote:3.1.0
com.android.support.test.espresso:espresso-web	androidx.test.espresso:espresso-web:3.1.0
com.android.support.test.janktesthelper:janktesthelper	androidx.test.jank:janktesthelper:1.0.1
com.android.support.test.services:test-services	androidx.test:test-services:1.1.0
com.android.support.test.uiautomator:uiautomator	androidx.test.uiautomator:uiautomator:2.2.0
com.android.support.test:monitor	androidx.test:monitor:1.1.0
com.android.support.test:orchestrator	androidx.test:orchestrator:1.1.0
com.android.support.test:rules	androidx.test:rules:1.1.0
com.android.support.test:runner	androidx.test:runner:1.1.0
com.android.support:animated-vector-drawable	androidx.vectordrawable:vectordrawable-animated:1.0.0
com.android.support:appcompat-v7	androidx.appcompat:appcompat:1.2.0
com.android.support:asynclayoutinflater	androidx.asynclayoutinflater:asynclayoutinflater:1.0.0
com.android.support:car	androidx.car:car:1.0.0-alpha5
com.android.support:cardview-v7	androidx.cardview:cardview:1.0.0
com.android.support:collections	androidx.collection:collection:1.0.0
com.android.support:coordinatorlayout	androidx.coordinatorlayout:coordinatorlayout:1.0.0
com.android.support:cursoradapter	androidx.cursoradapter:cursoradapter:1.0.0
com.android.support:customtabs	androidx.browser:browser:1.0.0
com.android.support:customview	androidx.customview:customview:1.0.0
com.android.support:design	com.google.android.material:material:1.0.0-rc01
com.android.support:documentfile	androidx.documentfile:documentfile:1.0.0
com.android.support:drawerlayout	androidx.drawerlayout:drawerlayout:1.0.0
com.android.support:exifinterface	androidx.exifinterface:exifinterface:1.0.0
com.android.support:gridlayout-v7	androidx.gridlayout:gridlayout:1.0.0
com.android.support:heifwriter	androidx.heifwriter:heifwriter:1.0.0
com.android.support:interpolator	androidx.interpolator:interpolator:1.0.0
com.android.support:leanback-v17	androidx.leanback:leanback:1.0.0
com.android.support:loader	androidx.loader:loader:1.0.0
com.android.support:localbroadcastmanager	androidx.localbroadcastmanager:localbroadcastmanager:1.0.0
com.android.support:media2	androidx.media2:media2:1.0.0-alpha03
com.android.support:media2-exoplayer	androidx.media2:media2-exoplayer:1.0.0-alpha01
com.android.support:mediarouter-v7	androidx.mediarouter:mediarouter:1.0.0
com.android.support:multidex	androidx.multidex:multidex:2.0.0
com.android.support:multidex-instrumentation	androidx.multidex:multidex-instrumentation:2.0.0
com.android.support:palette-v7	androidx.palette:palette:1.0.0
com.android.support:percent	androidx.percentlayout:percentlayout:1.0.0
com.android.support:preference-leanback-v17	androidx.leanback:leanback-preference:1.0.0
com.android.support:preference-v14	androidx.legacy:legacy-preference-v14:1.0.0
com.android.support:preference-v7	androidx.preference:preference:1.0.0
com.android.support:print	androidx.print:print:1.0.0
com.android.support:recommendation	androidx.recommendation:recommendation:1.0.0
com.android.support:recyclerview-selection	androidx.recyclerview:recyclerview-selection:1.0.0
com.android.support:recyclerview-v7	androidx.recyclerview:recyclerview:1.0.0
com.android.support:slices-builders	androidx.slice:slice-builders:1.0.0
com.android.support:slices-core	androidx.slice:slice-core:1.0.0
com.android.support:slices-view	androidx.slice:slice-view:1.0.0
com.android.support:slidingpanelayout	androidx.slidingpanelayout:slidingpanelayout:1.0.0
com.android.support:support-annotations	androidx.annotation:annotation:1.0.0
com.android.support:support-compat	androidx.core:core:1.0.0
com.android.support:support-content	androidx.contentpager:contentpager:1.0.0
com.android.support:support-core-ui	androidx.legacy:legacy-support-core-ui:1.0.0
com.android.support:support-core-utils	androidx.legacy:legacy-support-core-utils:1.0.0
com.android.support:support-dynamic-animation	androidx.dynamicanimation:dynamicanimation:1.0.0
com.android.support:support-emoji	androidx.emoji:emoji:1.0.0
com.android.support:support-emoji-appcompat	androidx.emoji:emoji-appcompat:1.0.0
com.android.support:support-emoji-bundled	androidx.emoji:emoji-bundled:1.0.0
com.android.support:support-fragment	androidx.fragment:fragment:1.0.0
com.android.support:support-media-compat	androidx.media:media:1.0.0
com.android.support:support-tv-provider	androidx.tvprovider:tvprovider:1.0.0
com.android.support:support-v13	androidx.legacy:legacy-support-v13:1.0.0
com.android.support:support-v4	androidx.legacy:legacy-support-v4:1.0.0
com.android.support:support-vector-drawable	androidx.vectordrawable:vectordrawable:1.0.0
com.android.support:swiperefreshlayout	androidx.swiperefreshlayout:swiperefreshlayout:1.0.0
com.android.support:textclassifier	androidx.textclassifier:textclassifier:1.0.0
com.android.support:transition	androidx.transition:transition:1.0.0
com.android.support:versionedparcelable	androidx.versionedparcelable:versionedparcelable:1.0.0
com.android.support:viewpager	androidx.viewpager:viewpager:1.0.0
com.android.support:wear	androidx.wear:wear:1.0.0
com.android.support:webkit	androidx.webkit:webkit:1.0.0

参考文章：
【google官方】androix包
【google官方】现有项目迁移教程