Installation failed with message INSTALL_FAILED_USER_RESTRICTED.
It is possible that this issue is resolved by uninstalling an existing version of the apk if it is present, and then re-installing.WARNING: Uninstalling will remove the application data!
Do you want to uninstall the existing application?
遇到这个问题的原因是真机测试代码时，很多手机是默认开启了USB安装管理，解决这个问题只需要关闭USB安装管理即可。
打开手机管家--点击权限管理--点击USB安装管理--关闭USB安装管理；或者把安装管理列出的被监控的应用设置成允许。
《转自 https://blog.csdn.net/delong_liu/article/details/79637987》