ShouldChangeTextInRange is not called for UITextView - ios

Question

I user custom UITextView and need to hide keyboard on return click. I need to catch 'ShouldChangeTextInRange' what has textview, I don't know why but
method is not called. here is code of for my text view :
public class PlaceholderTextView : UITextView
{
public PlaceholderTextView ()
{
Initialize ();
}
public PlaceholderTextView (CGRect frame)
: base (frame)
{
Initialize ();
}
public PlaceholderTextView (IntPtr handle)
: base (handle)
{
Initialize ();
}
void Initialize ()
{
Text = Placeholder;
ShouldBeginEditing = t => {
if (Text == Placeholder)
Text = string.Empty;
return true;
};
ShouldEndEditing = t => {
if (string.IsNullOrEmpty (Text))
Text = Placeholder;
return true;
};
}
public override bool ShouldChangeTextInRange (UITextRange inRange, string replacementText)
{
if (Text.Equals ("\n")) {
this.EndEditing (true);
return false;
} else {
return true;
}
}
}

Answer 1

In your UITextView subclass, add IUITextViewDelegate and implement ShouldChangeText (selector = textView:shouldChangeTextInRange:replacementText:):
public class MyTextView : UITextView, IUITextViewDelegate
{
string Placeholder;
public MyTextView()
{
Initialize();
}
public MyTextView(Foundation.NSCoder coder) : base(coder)
{
Initialize();
}
public MyTextView(Foundation.NSObjectFlag t) : base(t)
{
Initialize();
}
public MyTextView(IntPtr handle) : base(handle)
{
Initialize();
}
public MyTextView(CoreGraphics.CGRect frame) : base(frame)
{
Initialize();
}
public MyTextView(CoreGraphics.CGRect frame, NSTextContainer textContainer) : base(frame, textContainer)
{
Initialize();
}
void Initialize()
{
Delegate = this;
}
[Export("textViewShouldBeginEditing:")]
public bool ShouldBeginEditing(UITextView textView)
{
if (Text == Placeholder)
Text = string.Empty;
return true;
}
[Export("textViewShouldEndEditing:")]
public bool ShouldEndEditing(UITextView textView)
{
if (string.IsNullOrEmpty(Text))
Text = Placeholder;
return true;
}
[Export("textView:shouldChangeTextInRange:replacementText:")]
public bool ShouldChangeText(UITextView textView, NSRange range, string text)
{
if (text.Contains("\n"))
{
this.EndEditing(true);
return false;
}
return true;
}
}
Note: You can not mix using ObjC/Swift style Delegates and C# anonymous Delegates, otherwise you end up with the error:
Event registration is overwriting existing delegate. Either just use events or your own delegate