限制 Xamarin.Forms 中输入字段的输入长度和字符 [英] Restricting input length and characters for Entry field in Xamarin.Forms

问题描述

如何限制在 Xamarin.Forms 的 Entry 控件中输入的长度和字符.我需要创建自定义控件吗?有没有一种方法可以从 Entry(或其他控件)中派生出来，以便我可以应用必要的每个平台输入限制.

How can I restrict the length and characters entered in an Entry control in Xamarin.Forms. Do I need to create a custom control? Is there a way I can derive from Entry (or another control) so I can apply the necessary per-platform input limitations.

一个例子是一个数字字段，限制为最多 3 个字符，仅限数字.

An example would be a numeric field that is restricted to a maximum of 3 characters, digits only.

将 Entry 控件的 Keyboard 属性设置为 Keyboard.Numeric 仅为 iOS 设置键盘.它不限制实际的文本输入 - 即我仍然可以输入非数字字符.我也没有看到限制条目长度的方法.

Setting the Keyboard property of an Entry control to Keyboard.Numeric only sets the keyboard for iOS. It does not restrict the actual text entry - i.e. I can still enter non-digit characters. Nor do I see a way to limit the length of entry.

推荐答案

您可以限制输入字段中的字符数，如下所示，

You can restrict the number of charecters in the Entry field as given below,

  int restrictCount = <your restriction length> //Enter your number of character restriction
  Entry entry = new Entry();
  entry.TextChanged += OnTextChanged;

  void OnTextChanged(object sender, EventArgs e)
  {
    Entry entry = sender as Entry;
    String val = entry.Text; //Get Current Text

    if(val.Length > restrictCount)//If it is more than your character restriction
    {
     val = val.Remove(val.Length - 1);// Remove Last character 
     entry.Text = val; //Set the Old value
    }
  }

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