AndroidX是一个开源项目，Android团队使用它在Jetpack中开发、测试、打包、版本和发布库。

AndroidX是对原来的Android支持库的一个重大改进。像支持库一样，AndroidX与Android操作系统分开发布，并提供跨Android版本的向后兼容性。AndroidX通过提供特性校验和新库完全取代了支持库。

AndroidX包含以下特性:

All packages in AndroidX live in a consistent namespace starting with the string androidx. The Support Library packages have been mapped into the corresponding androidx.* packages. For a full mapping of all the old classes and build artifacts to the new ones, see the Package Refactoring page. Unlike the Support Library, AndroidX packages are separately maintained and updated. The androidx packages use strict Semantic Versioning starting with version 1.0.0. You can update AndroidX libraries in your project independently. All new Support Library development will occur in the AndroidX library. This includes maintenance of the original Support Library artifacts and introduction of new Jetpack components.

使用AndroidX

参见迁移到AndroidX了解如何迁移现有项目。

如果你想在一个新项目中使用AndroidX，你需要将编译SDK设置为Android 9.0 (API级别28)或更高，并在你的Gradle中将以下两个Android Gradle插件标志设置为true。属性文件。

android。useAndroidX:当设置为true时，Android插件使用适当的AndroidX库而不是支持库。国旗 如果未指定，则默认为false。 android。enableJetifier:当设置为true时，Android插件会自动迁移现有的第三方库，通过重写它们的二进制文件来使用AndroidX。缺省情况下，该标志为false 未指定。

对于工件映射，请参见此

Android Jetpack:最近的公告对Android的支持库意味着什么?解释得很好

Today, many consider the Support Library an essential part of Android app development, to the point where it’s used by 99 percent of apps in the Google Play store. However, as the Support Library has grown, inconsistencies have crept in surrounding the library’s naming convention. Initially, the name of each package indicated the minimum API level supported by that package, for example, support-v4. However, version 26.0.0 of the Support Library increased the minimum API to 14, so today many of the package names have nothing to do with the minimum supported API level. When support-v4 and the support-v7 packages both have a minimum API of 14, it’s easy to see why people get confused! To clear up this confusion, Google is currently refactoring the Support Library into a new Android extension library (AndroidX) package structure. AndroidX will feature simplified package names, as well as Maven groupIds and artifactIds that better reflect each package’s content and its supported API levels. With the current naming convention, it also isn’t clear which packages are bundled with the Android operating system, and which are packaged with your application’s APK (Android Package Kit). To clear up this confusion, all the unbundled libraries will be moved to AndroidX’s androidx.* namespace, while the android.* package hierarchy will be reserved for packages that ship with the Android operating system.

AndroidX是一个开源项目，Android团队使用它在Jetpack中开发、测试、打包、版本和发布库。

经过几个小时的努力，我通过在app/build.gradle中包含以下内容来解决这个问题:

android {
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
}

把这些标志放在gradle.properties中

android.enableJetifier=true
android.useAndroidX=true

Changes in gradle:

implementation 'androidx.appcompat:appcompat:1.0.2'
implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
implementation 'androidx.legacy:legacy-support-v4:1.0.0'
implementation 'com.google.android.material:material:1.1.0-alpha04'

当在Android studio上迁移时，app/gradle文件会自动更新标准库中的修正库实现

参考网址:https://developer.android.com/jetpack/androidx/migrate

Android提供了几个不同的库集。一个叫Android支持库，另一个叫AndroidX。选择“使用android。”* artifacts”表示我们想要使用AndroidX。

我是从这个Android开发峰会的视频中了解AndroidX的。总结是-

No more support library: The android support library will be never maintained by Google under the support library namespace. So if you want to find fixes of a bug in support library you must have to migrate your project in AndroidX Better package management: For standardized and independent versioning.Because previous support library versioning was too confusing. It will release you the pain of “All com.android.support libraries must use the exact same version specification” message. Other Good libraries have migrated to AndroidX: Google play services, Firebase, Mockito 2, etc are migrated to AndroidX. New libraries will be published using AndroidX artifact: All the libraries will be in the AndroidX namespace like Android Jetpack

它与AppCompat版本的支持相同，但它的v4和v7版本的混乱较少，因此使用android XML元素的不同组件有很大帮助。