Duplicate class android.support.v4.app.INotificationSideChannel found in modules core-1.1.0-runtime.

1.错误如下：

Duplicate class android.support.v4.app.INotificationSideChannel found in modules core-1.1.0-runtime.jar (androidx.core:core:1.1.0) and support-compat-26.1.0-runtime.jar (com.android.support:support-compat:26.1.0)

2.解决方法：

在gradle.properties中添加以下内容

android.useAndroidX=true
android.enableJetifier=true

然后同步一下