SDK 17版本增加了UserManager，所以找不到.您可以查看此链接了解详情.

the UserManager is added in SDK version of 17, so it can not find it. you can see this link for details.

如果你想使用它，你必须在android native中添加支持库.com.android.support:support-compat:28.0.0-alpha1 有它.

if you want to use it, you have to in the android native add support library. the com.android.support:support-compat:28.0.0-alpha1 has it.

如果您添加了 androidX 库，您应该将类​​更改为 UserManagerCompat.有关详细信息，您可以进入此链接它位于 androidX.core 中.在 android/app/build.gradle

if you have added the androidX library, you should change the class to UserManagerCompat. for details, you can go into this link it is located in androidX.core. add the following at android/app/build.gradle

def core_role_version = "1.0.0-alpha01"
implementation "androidx.core:core-role:$core_role_version"