c# – 在Monotouch中对UITextField进行子类化和重写

2023年8月19日 203次阅读

我试图将UITextField的占位符文本设置为不同的颜色.我了解到我需要子类化并覆盖drawPlaceholderInRect方法.

iPhone UITextField – Change placeholder text color

    (void) drawPlaceholderInRect:(CGRect)rect {
    [[UIColor blueColor] setFill];
    [[self placeholder] drawInRect:rect withFont:[UIFont systemFontOfSize:16]];
}

这是我到目前为止所做的,但我无法弄清楚如何才能做到恰到好处.我在最后一行感到困惑,因为我不知道如何将它映射到MonoTouch / C#对象.

using System;
using MonoTouch.UIKit;
using MonoTouch.Foundation;
using System.Drawing;

namespace MyApp
{
    [Register("CustomUITextField")]
    public class CustomUITextField:UITextField
    {
        public CustomUITextField () :base()
        {

        }

        public CustomUITextField (IntPtr handle) :base(handle)
    {

    }    

        public override void DrawPlaceholder (RectangleF rect)
        {       

            UIColor col = new UIColor(0,0,255.0,0.7);
            col.SetFill();
            //Not sure what to put here
            base.DrawPlaceholder (rect);}
    }
}

最佳答案 原始的ObjC代码不会调用super(它的基本方法)而是drawInRect：.您是否尝试过使用MonoTouch？例如

public override void DrawPlaceholder (RectangleF rect)
{
    using (UIFont font = UIFont.SystemFontOfSize (16))
    using (UIColor col = new UIColor (0,0,255.0,0.7)) {
        col.SetFill ();
        base.DrawString (rect, font);
    }
}

注意：drawInRect：WithFont：映射到C#中的DrawString扩展方法(可以在任何字符串上调用).

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