AndroidX相关

摘要：如何升级到androidX，androidX中一些类库的变化

升级到androidX

原文

简介

AndroidX是android.support.xxx整理后的产物。是由于之前的support包过于混乱。

迁移步骤

修改当前项目的gradle.properties

#表示当前项目启用 AndroidX
android.useAndroidX=true
#表示依赖包也迁移到 AndroidX
android.enableJetifier=true

如何迁移

在AndroidStudio3.2+版本中：Refactor–》Migrate to AndroidX（注意要提前备份）

迁移后续

手动修改错误包名

部分控件的包名/路径名转换有问题，需要手动调整（包括xml布局文件和.java或.kt文件）

如：ViewPager、RecyclerView等，包名变成android.core.weight.xxxx这是错误的包名，需要手动修改。

修复DataBinding中的错误（重名id错误）

去除attr.xml中重复的属性名称

Glide 中的注解不兼容AndroidX

规范包名（即文件夹名）

修改未自动迁移的三方库

莫名问题的解决

修复项目默认启用 androidx 的情况

AndroidX与Jetpack

• Jetpack是一套库、工具和指南；AndroidX是Android团队用于在Jetpack中开发、测试、打包和发布库以及对其进行版本控制的开源项目。
• Jetpack组件是AndroidX库的一部分。
• AndroidX可完全取代支持库（android.support*），不仅提供同等的功能，而且提供了新的库。

官方链接推荐

Android Jetpack

AndroidX 概览

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

Annotations API

AndroidX踩坑指南

转成AndroidX的原因

• 主动原因：Support 包从 API 28 （Android 9.0）已经弃更，取而代之的是谷歌新推出的 AndroidX 的包。
• 被动原因：现在一些第三方库都是直接依赖 AndroidX 包，由于谷歌限制 Support 包和 AndroidX 包不能共存的机制，导致我们无法直接依赖第三方库的最新版本，例如某个框架的最新版的依赖就是基于 AndroidX 包，这样就导致我们只能去依赖旧版的框架，无法使用最新框架。

转成AndroidX的步骤

Android Studio：Refactor》Migrate to Android X…

Studio帮我们做了什么事

• 自动替换导入类和xml中的View包名

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

<android.support.v7.widget.RecyclerView />
<androidx.recyclerview.widget.RecyclerView />

• Support 远程依赖变化

implementation 'com.android.support:appcompat-v7:28.0.0'
implementation 'com.android.support:design:28.0.0'

implementation 'androidx.appcompat:appcompat:1.0.0'
implementation 'com.google.android.material:material:1.0.0'

• gradle.properties 配置变化

# 表示使用 AndroidX
android.useAndroidX = true
# 表示将第三方库迁移到 AndroidX
android.enableJetifier = true

踩坑

坑一：找不到约束布局

• 这个因为 AndroidX 包中并没有依赖 ConstraintLayout 库，只需要手动加入依赖即可

  implementation 'androidx.constraintlayout:constraintlayout:2.0.0'

坑二：导包报错

• 部分导包报错，只需要手动更换引用的包名即可，这里不指定包名 Studio 自动会帮我们导入默认的

坑三：第三方库的坑

• 虽然在这次转换的过程中没有出现过这种异常，但是根据以往的经验，这两个第三方库很可能会导致编译不通过

  implementation 'com.jakewharton:butterknife:9.0.0'
  annotationProcessor 'com.jakewharton:butterknife-compiler:9.0.0'
  
  implementation 'com.github.bumptech.glide:glide:4.7.1'
  annotationProcessor 'com.github.bumptech.glide:compiler:4.7.1'

• 这个是因为这两个库的旧版本依赖 Support 包导致的，所以解决的方式是将这两个库升级到最新版本即可

  implementation 'com.jakewharton:butterknife:10.2.1'
  annotationProcessor 'com.jakewharton:butterknife-compiler:10.2.1'
  implementation 'com.github.bumptech.glide:glide:4.11.0'
  annotationProcessor 'com.github.bumptech.glide:compiler:4.11.0'

坑四：替换不干净

• Studio 只能帮我们替换显式调用的包名，而不能帮我们替换隐式调用的包名，例如通过反射填写的包名，混淆规则等等

  Class.forName("android.support.design.widget.Snackbar");
  Class.forName("android.support.design.widget.BottomSheetDialog");
  
  -keep class android.support.**{*;}

  解决的方式也很简单，在项目中全局搜索 android.support 关键字眼，然后手动进行替换

坑五：Fragment 封装

• 升级 AndroidX 后，切换 Fragment 出现NullPointerException:androidx.fragment.app.FragmentManagerImpl.isDestroyed() 异常，经过排查是 Fragment 基类中存在这些反射的代码导致的

  public abstract class BaseFragment extends Fragment {
  
      @Override
      public void onDetach() {
          super.onDetach();
          try {
              Field childFragmentManager = Fragment.class.getDeclaredField("mChildFragmentManager");
              childFragmentManager.setAccessible(true);
              childFragmentManager.set(this, null);
          } catch (NoSuchFieldException e) {
              throw new RuntimeException(e);
          } catch (IllegalAccessException e) {
              throw new RuntimeException(e);
          }
      }
  }

  这些代码是为了解决 Fragment 相互切换出现崩溃的 Bug，而这个 Bug 在 AndroidX 的版本已经被官方修复了，所以解决方案是删除掉这些代码即可。

  如果你对这个 Bug 感兴趣，可以点击此处了解：Getting the error “Java.lang.IllegalStateException Activity has been destroyed” when using tabs with ViewPager

常见误区：FileProvider

• 关于 FileProvider 的清单注册，没转 AndroidX 之前是这样子的

  <provider
      android:name="android.support.v4.content.FileProvider"
      android:authorities="${applicationId}.provider"
      android:exported="false"
      android:grantUriPermissions="true">
  
      <meta-data
          android:name="android.support.FILE_PROVIDER_PATHS"
          android:resource="@xml/file_paths" />
  </provider>

• 转成 AndroidX 之后的是这样子的

  <provider
      android:name="androidx.core.content.FileProvider"
      android:authorities="${applicationId}.provider"
      android:exported="false"
      android:grantUriPermissions="true">
  
      <meta-data
          android:name="android.support.FILE_PROVIDER_PATHS"
          android:resource="@xml/file_paths" />
  </provider>

其中的android.support.FILE_PROVIDER_PATHS不能自己改成androidX.。。。

Jetpack问题

“ViewDataBinding.getRoot() on a null object reference”

组件化开发的时候，报上面这个问题。

解决：

1. 宿主src的包名与组件下src的包名不能一样
2. 宿主对组件要用implementation，而不是runtime

…DataBinderMapperImpl.java:9: 错误: 找不到符号

D:\code\MyTests\MVVMDemo\app\build\generated\ap_generated_sources\debug\out\com\ab\mvvmdemo\DataBinderMapperImpl.java:9: 错误: 找不到符号
import com.ab.mvvmdemo.databinding.ActivityMainBindingImpl;
                                  ^
  符号:   类 ActivityMainBindingImpl
  位置: 程序包 com.ab.mvvmdemo.databinding

解决：十有八九是xml报错了。“排除法”排查xml的错误

ViewModelProvider.AndroidViewModelFactory.getInstance(getApplication()).create(UserViewModel.class); 报 RuntimeException

解决：在此处断点，跟进去看具体报错【最后发现是关联的其他的实例需要在MyApplication中获取。而MyApplication没有在清单中进行实例化导致的】