1、各种优秀UI例子
https://github.com/jsuarezruiz/xamarin-forms-goodlooking-UI
输入框例子
https://github.com/enisn/Xamarin.Forms.InputKit
浮动操作按钮
https://github.com/SuavePirate/Xamarin.Forms.Controls.FloatingActionButton
选项卡按钮
https://github.com/UdaraAlwis/XFSegmentedControl
圆形按钮
https://github.com/wilsonvargas/ButtonCirclePlugin
动画按钮
https://github.com/xamarinium/ButtonWithActivityIndicator
自定义后退按钮
https://github.com/bbl-Laobu/CustomBackIconDemo
图片按钮
https://github.com/DelcoigneYves/Xam.Plugin.ImageButton
https://github.com/mariusmuntean/SimpleImageButton
工具栏按钮
https://github.com/AmitManchanda/iOSSecondaryToolbarMenubar
https://github.com/wilsonvargas/GradientNavigationToolbarXamarinForms
导航栏bar自定义
https://github.com/thrive-now/BottomNavigationBarXF
https://github.com/CrossGeeks/CustomNavigationBarSample
本地通知插件：
https://github.com/thudugala/Plugin.LocalNotification
手写签名
https://github.com/xamarin/SignaturePad
https://github.com/search?l=C%23&p=2&q=signature&type=Repositories
Picker例子，下拉列表、时间选择器
https://github.com/amay077/Xamarin_Forms_PickerViewSample 下拉列表
https://github.com/brminnick/InvestmentDataSampleApp 下拉列表，自动补全
https://github.com/CrossGeeks/ClearableDatePickerSample 时间选择器
https://github.com/kirtisagar/XamarinFormsRadioButtonXAML 单选
