xamarin.forms如何通过Entry选择所有焦点文字？

Question

我知道Xamarin.Android代码，但是Xamarin.IOS呢？

Xamarin.Android代码：

public class CustomNumEntry : EntryRenderer
{
    public CustomNumEntry(Context context) : base(context)
    {
    }
    protected override void OnElementChanged(ElementChangedEventArgs<Entry> e)
    {
        base.OnElementChanged(e);
        if (this.Control != null)
        {
            Control.SetPadding(10, 0, 0, 15);
            Control.InputType = Android.Text.InputTypes.ClassNumber | Android.Text.InputTypes.NumberFlagSigned | Android.Text.InputTypes.NumberFlagDecimal;
            Control.TextAlignment = Android.Views.TextAlignment.Center;


        }
        if (e.OldElement == null)
        {
            var nativeEditText = (global::Android.Widget.EditText)Control;
            nativeEditText.SetSelectAllOnFocus(true);
        }

    }
}

Answer 1

对于Xamarin iOS：

nativeTextField.EditingDidBegin += (object sender, EventArgs eIos) =>
                {
                   nativeTextField.PerformSelector(new Selector("selectAll"), null, 0.0f);
                };

使用自定义渲染器（适用于iOS）的Xamarin.Forms（您正在寻找）：

    public class CustomNumEntry : EntryRenderer
    {
        protected override void OnElementChanged(ElementChangedEventArgs<Entry> e)
        {
            base.OnElementChanged(e);    
            if (Control != null)
            {
                var nativeTextField = (UITextField)Control;    
                nativeTextField.EditingDidBegin += (object sender, EventArgs eIos) =>
                {
                   nativeTextField.PerformSelector(new Selector("selectAll"), null, 0.0f);
                };                           
            }
        }

    }

Answer 2

解决方案：

您可以在方法 EditingStarted 中实现它。请参考以下代码

namespace xxx.iOS
{
  public class MyEntryRenderer:EntryRenderer,IUITextFieldDelegate
  {
    public MyEntryRenderer()
    {


    }

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

        if(Control!=null)
        {
            Control.WeakDelegate = this;   

        }

    }


    [Export("textFieldDidBeginEditing:")]
    public void EditingStarted(UITextField textField)
    {
        textField.PerformSelector(new Selector("selectAll:"), null, 0.0f);
    }

  }
}