Question

您好我正在尝试在Android中为boxview制作渲染器。我需要添加渲染新视图。视图无法显示。有人可以告诉我什么是错的并解释我是否有效？

这是我的渲染器中的方法。

     protected override void OnElementChanged(ElementChangedEventArgs<BoxView> e) {
        base.OnElementChanged(e);

        var activity = this.Context as Activity;

        if (e.OldElement == null) {
            // Connect the control to its renderer.
            PKInputView inputView = (PKInputView)this.Element;

            var viewGroup = (global::Android.Views.ViewGroup)ViewGroup;

            //Creating Layout
            global::Android.Widget.RelativeLayout layout = new global::Android.Widget.RelativeLayout(viewGroup.Context);
            //Creating TextView
            global::Android.Widget.TextView text = new global::Android.Widget.TextView(this.Context);
            text.Text = "ahoj";
            text.SetHeight(30);
            text.SetTextColor(global::Android.Graphics.Color.Red);

            //Set up layers
            layout.AddView(text);
            viewGroup.AddView(layout);
        }

Answer 1

将e.OldElement替换为this.Control：

if (this.Control == null) {

删除它，因为它会引发异常（除非BoxView继承自PKInputView）：

    PKInputView inputView = (PKInputView)this.Element;

然后在if语句范围的末尾设置本机视图：

    this.SetNativeControl(viewGroup);
}

我认为渲染器看起来像这样：

public class BoxViewRenderer : ViewRenderer<BoxView, global::Android.Views.ViewGroup>

Answer 2

我必须包括全班，因为你的建议不起作用。

[assembly: ExportRenderer(typeof(PKInputView), typeof(PKInputViewRenderer))]

namespace takeapayment.Droid.Renderers {

public class PKInputViewRenderer : BoxRenderer, CCDataSource {
    /*
    //header
    private global::Android.Widget.AbsoluteLayout header = Android.Widget.AbsoluteLayout();
    private TextView title = new TextView();
    private global::Android.Widget.Button saveButton = new Button();
    */

    protected void OnCreate(Bundle savedInstanceState) {
        this.OnCreate(savedInstanceState);

    }

    protected override void OnElementChanged(ElementChangedEventArgs<BoxView> e) {
        base.OnElementChanged(e);

        var activity = this.Context as Activity;

        if (e.OldElement == null) {
            // Connect the control to its renderer.
            PKInputView inputView = (PKInputView)this.Element;

            var viewGroup = (global::Android.Views.ViewGroup)ViewGroup;

            //Creating Layout
            global::Android.Widget.RelativeLayout layout = new global::Android.Widget.RelativeLayout(viewGroup.Context);
            //Creating TextView
            global::Android.Widget.TextView text = new global::Android.Widget.TextView(this.Context);
            text.Text = "ahoj";
            text.SetHeight(30);
            text.SetTextColor(global::Android.Graphics.Color.Red);

            //Set up layers
            layout.AddView(text);
            viewGroup.AddView(layout);
        }
    }

}

Answer 3

如果要替换控件，则应从viewrenderer派生渲染器。试试这些代码。而这个vdo

[assembly: ExportRenderer(typeof(PKInputView), typeof(PKInputViewRenderer))]

public class PKInputViewRenderer : ViewRenderer<PKInputView,global::Android.Widget.TextView>, CCDataSource
{
    protected override void OnElementChanged(ElementChangedEventArgs<PKInputView> e)
    {
        base.OnElementChanged(e);

        // Connect the control to its renderer.
        PKInputView inputView = e.NewElement ?? e.OldElement;;

        // Creating TextView
        global::Android.Widget.TextView text = new global::Android.Widget.TextView(this.Context);
        text.Text = "ahoj";
        text.SetHeight(30);
        text.SetTextColor(global::Android.Graphics.Color.Red);

        SetNativeControl(text);
    }
}

Answer 4

此vdo将显示自定义渲染器的所有方面。 https://developer.xamarin.com/videos/cross-platform/xamarinforms-custom-renderers/

xamarin替换渲染器中的新视图

4 个答案: