1.使用小米系列的真机调试遇到的问题，弹框如下：
Installation failed with message INSTALL_CANCELED_BY_USER.
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
2.出现这个问题的原因是：开发者选项中的usb安装未打开，只要打开就行了。
打开目录如下：