Xamarin表单中的占位符文本对齐方式

Question

我不知道如何在输入框中放置占位符文本。 我有一个非常大的输入框，并希望将占位符文本放在顶部。

<Entry Placeholder="Enter notes about the item" 
     Keyboard="Text" VerticalOptions="Start" HeightRequest="80" /> 

Answer 1

您需要为每个平台创建一个自定义渲染到阿玲占位符是这样的：

public class PlaceholderEditor : Editor 
{ 
    public static readonly BindableProperty PlaceholderProperty = 
     BindableProperty.Create<PlaceholderEditor, string>(view => view.Placeholder, String.Empty); 

    public PlaceholderEditor() 
    { 
    } 

    public string Placeholder 
    { 
     get 
     { 
      return (string)GetValue(PlaceholderProperty); 
     } 

     set 
     { 
      SetValue(PlaceholderProperty, value); 
     } 
    } 
} 

public class PlaceholderEditorRenderer : EditorRenderer 
{ 
    public PlaceholderEditorRenderer() 
    { 
    } 

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

     if (e.NewElement != null) 
     { 
      var element = e.NewElement as PlaceholderEditor; 
      this.Control.Hint = element.Placeholder; 
     } 
    } 

    protected override void OnElementPropertyChanged(
     object sender, 
     PropertyChangedEventArgs e) 
    { 
     base.OnElementPropertyChanged(sender, e); 

     if (e.PropertyName == PlaceholderEditor.PlaceholderProperty.PropertyName) 
     { 
      var element = this.Element as PlaceholderEditor; 
      this.Control.Hint = element.Placeholder; 
     } 
    } 
}