在 Monotouch 中继承和覆盖 UITextField [英] Subclassing and overriding UITextField in Monotouch

问题描述

我正在尝试将 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 - 更改占位符文本颜色

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

这是我到目前为止所拥有的，但我不知道如何正确使用它.我对最后一行感到困惑，因为我不知道如何将其映射到 MonoTouch/C# 对象.

使用系统；使用 MonoTouch.UIKit；使用 MonoTouch.Foundation；使用 System.Drawing；命名空间 MyApp{[注册(CustomUITextField")]公共类 CustomUITextField:UITextField{公共 CustomUITextField () :base(){}public CustomUITextField (IntPtr handle) :base(handle){}公共覆盖无效 DrawPlaceholder (RectangleF rect){UIColor col = new UIColor(0,0,255.0,0.7);col.SetFill();//不知道该放什么base.DrawPlaceholder(矩形)；}}}

解决方案

原始的 ObjC 代码不调用 super(它的基本方法)而是 drawInRect:.您是否尝试过使用 MonoTouch 进​​行相同操作?例如

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

注意:drawInRect:WithFont: 映射到 C# 中的 DrawString 扩展方法(可以在任何 string 上调用).>

I am trying to set the placeholder text for a UITextField to a different color. I have learned that I need to subclass and override drawPlaceholderInRect method.

iPhone UITextField - Change placeholder text color

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

Here is what I have so far, but I just can't figure out how to get it just right. I am confused on the last line as I don't know how to map this to MonoTouch/C# objects.

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);}
    }
}

解决方案

The original ObjC code does not call super (it's base method) but drawInRect:. Have you tried the same with MonoTouch ? e.g.

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);
    }
}

Note: drawInRect:WithFont: maps to the DrawString extension method in C# (which can be called on any string).

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