c# iOS 无法将光标定位在 UITextField 中的位置 1

Question

无论我做什么，我都无法将光标设置到此字符串中的位置 1 (___) ___-____ 位置 1 是紧跟在开头 ( 之后的位置。我在委托的 EditingStarted 方法中执行此操作，作为指南，我遵循代码。目前我的代码是：

    public override void EditingStarted(UITextField textField)
    {
        if (MyParent.EditMask != "")
        {
            textField.Text = MyParent.EditMask.Replace("#", "_");
            // Set cursor position
            NSRange therange = new NSRange(index, 0);
            UITextPosition start = textField.GetPosition(textField.BeginningOfDocument, therange.Length - 1);
            UITextPosition end = textField.GetPosition(start, therange.Length);
            textField.SelectedTextRange = textField.GetTextRange(start, end);
        }
    }

光标总是在关闭 ) 后立即出现，我没有做任何改变。我不知道为什么。我试过获取第一个下划线的位置：

int position = textField.Text.IndexOf("_");
NSRange therange = new NSRange(position, 0);

但同样，这会导致光标紧跟在结束 ) 之后。有人看出我做错了什么吗？

**** 更新 ****

为了让人们理解上下文，上面的代码是我创建的名为 UIMaskedTextField 的 class 的一部分，用于处理用户界面中的所有 mask/text 输入格式。 class 是：

class UIMaskedTextField : UITextField
{
    public string EditMask { get; set; }

    public UIMaskedTextField()
    {
        this.Delegate = new MaskTextViewDelegate(this);
    }

}
class MaskTextViewDelegate : UITextFieldDelegate
{
    private UIMaskedTextField MyParent;
    int index = 0;
    public MaskTextViewDelegate(UIMaskedTextField parent)
    {
        MyParent = parent;
    }

    public override void EditingStarted(UITextField textField)
    {
        if (MyParent.EditMask != "")
        {
            textField.Text = MyParent.EditMask.Replace("#", "_");
            // Set cursor position
            int position = textField.Text.IndexOf("_");

            NSRange therange = new NSRange(position, 0);
            UITextPosition start = textField.GetPosition(textField.BeginningOfDocument, therange.Location);
            UITextPosition end = textField.GetPosition(start, therange.Length);
            textField.SelectedTextRange = textField.GetTextRange(start, end);

        }
    }
    public override bool ShouldChangeCharacters(UITextField textField, NSRange range, string replacementString)
    {
        int fieldlength = 10; // MyParent.EditMask.Length;
        string text = textField.Text;
        int NeedASpace = MyParent.EditMask.IndexOf(" ");
        string newText = "";
        if (text == "")
        {
            newText = MyParent.EditMask.Replace("#", "_");
        } else
        {
            newText = text;
        }

        string totalChar = newText.Replace(" ", "");
        totalChar = totalChar.Replace("(", "");
        totalChar = totalChar.Replace(")", "");
        totalChar = totalChar.Replace("-", "");
        totalChar = totalChar.Replace("_", "");

        int val;
        if ((totalChar + replacementString).Length <= fieldlength) {
            if (replacementString != "")
            {
                index = newText.IndexOf("_");
                StringBuilder sb = new StringBuilder(newText);
                char character = char.Parse(replacementString);
                sb[index] = character;
                newText = sb.ToString();


                textField.Text = newText;

                // Set cursor to next position, this works flawlessly
                NSRange therange = new NSRange(index, 0);
                UITextPosition start = textField.GetPosition(textField.BeginningOfDocument, therange.Location + 1);
                UITextPosition end = textField.GetPosition(start, therange.Length);
                textField.SelectedTextRange = textField.GetTextRange(start, end);

                newText = "";
            }
            else
            { // Still working the backspace key, so not done here yet.
                if (text.Length > 1)
                {
                    newText = text.Substring(0, text.Length - 1);
                }
                else
                {
                    newText = "";
                }
            }
        }

        return Int32.TryParse(newText, out val);
    }
}

Answer 1

要将光标定位在 UITextField 中的位置 1：

public partial class ViewController : UIViewController
{
    public ViewController (IntPtr handle) : base (handle)
    {
    }

    UITextField textfield1 { get; set; }

    public override void ViewDidLoad ()
    {
        base.ViewDidLoad ();
        // Perform any additional setup after loading the view, typically from a nib.

        var frame = new CGRect(10, 10, 300, 40);
        textfield1 = new UITextField(frame);

        textfield1.Text = "(___) ___-____";
        textfield1.Delegate = new myDelegate();

        View.Add(textfield1);


        textfield1.BecomeFirstResponder();

    }
}

public class myDelegate : UITextFieldDelegate {

    public override void EditingStarted(UITextField textField)
    {
        var arbitraryValue = 1;

        var newPosition = textField.GetPosition(textField.BeginningOfDocument, arbitraryValue);
        textField.SelectedTextRange = textField.GetTextRange(newPosition, newPosition);
    }
}

更新:

public override void DidChangeSelection(UITextField textField)
{
    var arbitraryValue = 1;

    var newPosition = textField.GetPosition(textField.BeginningOfDocument, arbitraryValue);
    textField.SelectedTextRange = textField.GetTextRange(newPosition, newPosition);

}

Answer 2

好的，终于可以使用了。 @Jack Hua 的解决方案对我不起作用，因为我无法将文本字段设置为 FirstResponder，因为滚动视图上有许多 UIMaskedTextField，屏蔽的文本字段不是第一个 sub-views 在滚动视图上，但它确实给了我一些想法！我开始怀疑在设置文本属性时文本字段的初始化以某种方式搞砸了光标位置，我相信这就是正在发生的事情，只是无法证明它因为视图的初始化是发生在幕后。但是我怀疑通过 EditMask 属性设置视图的掩码使初始化发生得更快并且可以设置光标位置。这也从一开始就设置了掩码，消除了用户对字段格式的疑虑。这是我的“最终”代码：

class UIMaskedTextField : UITextField
{
    private string editmask = "";
    public String EditMask
    {
        get => editmask;
        set
        {
            if ((value != ""))
            {
                editmask = value;
                this.Text = editmask.Replace("#", "_"); ;
            }
        }
    }

    public UIMaskedTextField()
    {
        this.Delegate = new PhoneMaskTextViewDelegate(this);
    }
}

class PhoneMaskTextViewDelegate : UITextFieldDelegate
{
    private UIMaskedTextField MyParent;
    int index = 0;
    public PhoneMaskTextViewDelegate(UIMaskedTextField parent)
    {
        MyParent = parent;
    }

    public override void DidChangeSelection(UITextField textField)
    {
        // place the cursor in the first fill podition
        int y = textField.Text.IndexOf("_");

        if (y > -1)
        {
            var newPosition = textField.GetPosition(textField.BeginningOfDocument, y);
            textField.SelectedTextRange = textField.GetTextRange(newPosition, newPosition);
        }

    }
    public override bool ShouldChangeCharacters(UITextField textField, NSRange range, string replacementString)
    {
        const string maskCharacters = "()-/ ";

        string newText = "";
        int val;

        if (replacementString != "")
        {
            int fieldlength = 10; // MyParent.EditMask.Length;
            string text = textField.Text;
            if (text == "")
            {
                newText = MyParent.EditMask.Replace("#", "_");
            }
            else
            {
                newText = text;
            }

            string totalChar = newText.Replace(" ", "");
            totalChar = totalChar.Replace("(", "");
            totalChar = totalChar.Replace(")", "");
            totalChar = totalChar.Replace("-", "");
            totalChar = totalChar.Replace("_", "");

            if (Utils.IsNumeric(replacementString))
            {
                if ((totalChar + replacementString).Length <= fieldlength)
                {
                    if (replacementString != "")
                    {
                        index = newText.IndexOf("_");
                        if (index > -1)
                        {
                            StringBuilder sb = new StringBuilder(newText);
                            char character = char.Parse(replacementString);
                            sb[index] = character;
                            newText = sb.ToString();


                            textField.Text = newText;

                            // Set cursor to next position
                            NSRange therange = new NSRange(index, 0);
                            UITextPosition start = textField.GetPosition(textField.BeginningOfDocument, therange.Location + 1);
                            UITextPosition end = textField.GetPosition(start, therange.Length);
                            textField.SelectedTextRange = textField.GetTextRange(start, end);
                        }
                        newText = "";
                    }
                }
            }
        } else
        { // Backspace/Delete pressed

            UITextRange position = textField.SelectedTextRange;
            string x = position.ToString();
            int positionofcursor = Convert.ToInt32(x.Substring(x.IndexOf("(") + 1, x.IndexOf(",") - x.IndexOf("(") - 1));

            string characterInPosition = "";


            // make sure we're not deleting a mask character
            do {
                positionofcursor -= 1;
                if (positionofcursor > -1)
                {
                    characterInPosition = textField.Text.Substring(positionofcursor, 1);
                    int j = maskCharacters.IndexOf(characterInPosition);
                }else
                {
                    break;
                }
            } while (maskCharacters.IndexOf(characterInPosition) > -1);

            if (positionofcursor > -1)
            {
                StringBuilder sb = new StringBuilder(textField.Text);
                sb[positionofcursor] = char.Parse("_");
                textField.Text = sb.ToString();

                NSRange therange = new NSRange(positionofcursor, 0);
                UITextPosition start = textField.GetPosition(textField.BeginningOfDocument, therange.Location);
                UITextPosition end = textField.GetPosition(start, therange.Length);
                textField.SelectedTextRange = textField.GetTextRange(start, end);
            }
        }

        return Int32.TryParse(newText, out val);
    }
}

c# iOS 无法将光标定位在 UITextField 中的位置 1

c# iOS Can NOT position cursor in UITextField in position 1

c#

uitextfield

xamarin.ios

ios