Solution:
1. The first step is to uninstall the old ButterKnife plugin
File--"Settings---"Plugins option, find the Android ButterKnife Zelezny plugin in the Installed tab, and uninstall it. and reboot.
2. The second part, install the ButterKnife plug-in that supports AS 4.1 version, the name is: Android ButterKnife Injections (Support Kotlin), do not restart after the installation is complete.
3. Delete the legacy android-butterknife-zelezny.jar package (note: the distinction is not Android-ButterKnife-Injections.jar ).
The local path is: C:\Users\Administrator\.AndroidStudio4.0\config\plugins or C:\Users\Administrator\AppData\Local\Google\AndroidStudio4.1\plugins The android-butterknife-zelezny.jar package under this path delete it.
Administrator in the path is the user name of your own PC, which needs to be replaced according to the actual situation.
4. Restart Android Studio. In theory, you should right-click generate to have the ButterKnife option.
