我希望用户能够在UITextView
中输入不超过一些数字的字符。这也需要使用复制粘贴。我发现this solution但是它是Objective C,它有一个缺点,即在达到限制后重置光标位置。
我想要的是一个继承自UITextView
的类,公开MaxCharacters
属性并完成所有工作。
答案 0 :(得分:5)
此代码基于manicaesar's answer,但在达到限制后不会重置插入位置。
[Register ("LimitedTextView")]
public class LimitedTextView : UITextView
{
public int MaxCharacters { get; set; }
void Initialize ()
{
MaxCharacters = 140;
ShouldChangeText = ShouldLimit;
}
static bool ShouldLimit (UITextView view, NSRange range, string text)
{
var textView = (LimitedTextView)view;
var limit = textView.MaxCharacters;
int newLength = (view.Text.Length - range.Length) + text.Length;
if (newLength <= limit)
return true;
// This will clip pasted text to include as many characters as possible
// See https://stackoverflow.com/a/5897912/458193
var emptySpace = Math.Max (0, limit - (view.Text.Length - range.Length));
var beforeCaret = view.Text.Substring (0, range.Location) + text.Substring (0, emptySpace);
var afterCaret = view.Text.Substring (range.Location + range.Length);
view.Text = beforeCaret + afterCaret;
view.SelectedRange = new NSRange (beforeCaret.Length, 0);
return false;
}
public LimitedTextView (IntPtr handle) : base (handle) { Initialize (); }
public LimitedTextView (RectangleF frame) : base (frame) { Initialize (); }
}