| id | title | subtitle |
|---|---|---|
40066284-0D92-4F3C-888D-7F08D381F8B2 |
Validate Text Input |
And Show Errors |
One of the easiest ways to show validation errors in iOS is to highlight the border of the text field. This Recipe shows how to do just that either after the user has entered text, or via a button press.
The EditingDidEnd event is raised when a user moves focus from a control,
either from selecting the next control, or from clicking the Done
button. The border properties on the text field can be accessed via the underlying Layer object:
// to validate after the user has entered text and moved away from that
// text field, use EditingDidEnd
this.FirstText.EditingDidEnd += (object sender, EventArgs e) => {
// perform a simple "required" validation
if ( ((UITextField)sender).Text.Length <= 0 ) {
// need to update on the main thread to change the border color
InvokeOnMainThread ( () => {
this.FirstText.BackgroundColor = UIColor.Yellow;
this.FirstText.Layer.BorderColor = UIColor.Red.CGColor;
this.FirstText.Layer.BorderWidth = 3;
this.FirstText.Layer.CornerRadius = 5;
} );
}
};
The result is the following:
Validation can also be done at the push of a button:
// we can also validate on the touch of a button
this.ValidateButton.TouchUpInside += (object sender, EventArgs e) => {
if ( this.SecondText.Text.Length <= 0 ) {
InvokeOnMainThread ( () => {
this.SecondText.BackgroundColor = UIColor.Cyan;
this.SecondText.Layer.BorderColor = UIColor.Brown.CGColor;
this.SecondText.Layer.BorderWidth = 3;
this.SecondText.Layer.CornerRadius = 5;
} );
}
};
The result is the following:
