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我正在使用 Xamarin 开发跨平台控件。我的目标是列出可选项目。我有一些运行良好的 iOS 代码：

    private UIView CreateViewWithTemplate(UIPickerView pickerView, nint row)
            {
                // create our content presenter
                DYMOContentPresenter presenter = new DYMOContentPresenter();

                // set its data template to the one from our control
                presenter.ItemTemplate = this._pickerControl.ItemTemplate;

                // set the data to the correct item from the list
                presenter.ObjectContent = this._pickerControl.Items.ElementAt((int)row);

                // and use the xamarin forms renderer factory to get a renderer for the item
                IVisualElementRenderer renderer = RendererFactory.GetRenderer(presenter);

                // tell the renderer the size of the view and 
                renderer.SetElementSize(new Size(pickerView.Frame.Width, ROW_HEIGHT));

                // then get the native view and return


 return renderer.NativeView;
        }

但是，我在 Android 中实现这一点的尝试不起作用：

private View CreateViewWithTemplate(int position, View convertView, ViewGroup parent)
{            
    // create content presenter
    DYMOContentPresenter presenter = new DYMOContentPresenter();

    // set its data template to the correct item from the list
    presenter.ItemTemplate = this._pickerControl.ItemTemplate;

    // set data to correct list item
    presenter.ObjectContent = this._pickerControl.Items.ElementAt((int) position);

    // use Xamarin forms renderer factory to get a renderer for the item
    IVisualElementRenderer renderer = RendererFactory.GetRenderer(presenter);

    presenter.Layout(new Xamarin.Forms.Rectangle(0, 0, parent.Width, ROW_HEIGHT));
    renderer.UpdateLayout();
    renderer.Tracker.UpdateLayout();
    renderer.ViewGroup.LayoutParameters = new ViewGroup.LayoutParams(parent.Width, ROW_HEIGHT);
    renderer.ViewGroup.Layout(0, 0, parent.Width, ROW_HEIGHT);
    renderer.ViewGroup.BuildDrawingCache();

    // get native view and return
    return renderer.ViewGroup;
}

我可以看到单个列表视图行，但其中没有出现任何文本。注释掉这段代码并将其替换为 simple 后，我可以看到文本TextView，所以我怀疑渲染器有问题。我也尝试了此代码的许多变体（指定LayoutParams、尝试调整孩子的大小等）。似乎没有任何效果。

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