您可能正在使用 android 5.0 或更高版本的设备.

You may be using the android 5.0 or above device.

可能是您的开发版本没有正确卸载.

试试这个，

只需转到设置 -->应用程序 -->单击您的应用程序.--->在操作栏菜单的应用信息页面中，将有一个名为"的选项.为所有用户卸载点击那个.您的应用程序将被完全卸载，现在您可以尝试安装新版本，没有问题.希望对你有帮助

Just go to the Settings --> Apps --> Click on your App. ---> In App info page at the action bar menu there will be an option called " Uninstall for All users " click that. Your app will be completely uninstalled and now you can try installing the new version with no issue. Hope this will help you

注意:这适用于棒棒糖及以上.请参阅随附的屏幕截图.

NOTE : This is for lollipop and above. Refer the screenshot attached.