xamarin.forms跳转android native并传参

xamarin开发过程中，能写在pcl的尽量写在pcl，提高复用率，但有时候因为一些已知的原因，不得不去使用native，xamarin官方github上有提供这部分源码Forms2Native供参考，这里以实际开发过程中实现xamarin android截图控件为例。

一、pcl中：SourcePage为调用方，CropPage.cs为目标页；

public SourcePage()
{InitializeComponent();var command = new Command(async () =>{//获取gallery中照片var mediaPicker = DependencyService.Get<IMediaPicker>();var result = await mediaPicker.SelectPhotoAsync(new CameraMediaStorageOptions { DefaultCamera = CameraDevice.Front, MaxPixelDimension = 400 });//创建CropPage并传入照片路径var desPage = new CropPage(result.Path);//跳转App.Current.MainPage = desPage;//跳转后会出现两个页面，实际上CropPage还是生成了，在点击左下方的返回按钮时回到的是CropPage而不是SourcePagae，//我这里是将原调用页重新指定回去，不知道其他人是怎么处理的，欢迎告知。App.Current.MainPage = new SourcePage();}); btnSelectPhoto.Command = command; 
}

二、CropPage.cs

public class CropPage : ContentPage
{//欲传往native的参数，写成公共属性供native中Renderers的OnCreate方法调用，这里为图片路径public string FilePath { get; set; }public CropPage(){}public CropPage(string filePath):this(){FilePath = filePath;}
}

三、xamarin android中，特定Renderer绑定CropPage和Renderer本身，这里为CropPageRenderer

//该特性实现CropPage和CropPageRenderer的绑定
[assembly:ExportRenderer(typeof(AppPortable.CropPage), typeof(App.Droid.Renderers.CropPageRenderer))]namespace App.Droid.Renderers
{public class CropPageRenderer : PageRenderer{protected override void OnElementChanged(ElementChangedEventArgs<Page> e){base.OnElementChanged(e);var filePath = "";if (e.NewElement != null){//这边获取CropPage所传递的参数filePath = (e.NewElement as CropPage).FilePath;}//开始运行指定的Activity，这里是CropActivityvar activity = this.Context as Activity;var cropActivity = new Intent(activity, typeof(CropActivity));activity.StartActivity(cropActivity);}}
}

四、xamarin android中的CropActivity.cs

namespace App.Droid
{[Activity(Label = "CropActivity")]public class CropActivity : Activity{protected override void OnCreate(Bundle savedInstanceState){base.OnCreate(savedInstanceState);//这边就完成了，至于layout目录下的axml目标axmlSetContentView(Resource.Layout.CropImage);}}
}