Custom inputView with dynamic height in iOS 8

Question

I have some trouble with my custom inputView for UITextFields. Depending on the text the user needs to input in a UITextField, the inputView displays only the needed letters. That means for short texts, an inputView with only one line of letters is sufficient, longer texts may require 2 or even 3 lines so the height of the inputView is variabel.

Since I was expecting better performance, there exists only one inputView instance that is used by every textField. That way the creation must only happen once and it made the sometimes needed direct access to the inputView easier. The inputView is set up in - (BOOL)textFieldShouldBeginEditing:(UITextField *)textField, sets its required height and will be shown.

That works perfectly, but not on iOS8. There some system view containing the inputView will not update its frame to match the inputView's bounds when they are changed (first time works).

I know that can be fixed by using one instance of my inputView per textField. But I'm asking if there is a recommended/better way to adjust the frame or to report its change to the containing view. Maybe it is an iOS8 bug that could be fixed until release?

Here's some example code to reproduce the issue:

CustomInputView

@implementation CustomInputView

+ (CustomInputView*)sharedInputView{
    static CustomInputView *sharedInstance;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        sharedInstance = [[CustomInputView alloc] init];
    });
    return sharedInstance;
}

- (id)init
{
    self = [super init];
    if (self) {
        self.backgroundColor = [UIColor greenColor];
    }
    return self;
}

- (void)setupForTextField:(UITextField*)textField{
    CGFloat height;

    if(textField.tag == 1){
        height = 100;
    }else height = 50;

    self.frame = CGRectMake(0, 0, 320, height);
}
@end

TestViewController code

- (void)viewDidLoad
{
    [super viewDidLoad];

    UITextField *tf = [[UITextField alloc] initWithFrame:CGRectMake(15, 50, 290, 30)];
    tf.text = @"bigKeyboard";
    tf.inputView = [CustomInputView sharedInputView];
    tf.layer.borderWidth = 1;
    tf.layer.borderColor = [UIColor lightGrayColor].CGColor;
    tf.delegate = self;
    tf.tag = 1;
    [self.view addSubview:tf];

    tf = [[UITextField alloc] initWithFrame:CGRectMake(15, 100, 290, 30)];
    tf.text = @"smallKeyboard";
    tf.inputView = [CustomInputView sharedInputView];
    tf.layer.borderWidth = 1;
    tf.layer.borderColor = [UIColor lightGrayColor].CGColor;
    tf.delegate = self;
    tf.tag = 2;
    [self.view addSubview:tf];

    UIButton *button = [UIButton buttonWithType:UIButtonTypeSystem];
    [button setTitle:@"dismissKeyboard" forState:UIControlStateNormal];
    [button addTarget:self action:@selector(endEditing) forControlEvents:UIControlEventTouchUpInside];
    button.frame = CGRectMake(15, 150, 290, 30);
    [self.view addSubview:button];
}

- (void)endEditing{
    [self.view endEditing:YES];
}

- (BOOL)textFieldShouldBeginEditing:(UITextField *)textField{
    [[CustomInputView sharedInputView] setupForTextField:textField];
    return YES;
}

Answer 1

I had similar issues with sizing a custom keyboard from iOS 8 to iOS 10. I believe the proper solution is to have the input view provide a proper intrinsicContentSize and change (and invalidate!) that value when you want to change the view's height. Sample code:

class CustomInputView: UIInputView {
    var intrinsicHeight: CGFloat = 200 {
        didSet {
            self.invalidateIntrinsicContentSize()
        }
    }

    init() {
        super.init(frame: CGRect(), inputViewStyle: .keyboard)
        self.translatesAutoresizingMaskIntoConstraints = false
    }

    required init?(coder: NSCoder) {
        super.init(coder: coder)
        self.translatesAutoresizingMaskIntoConstraints = false
    }

    override var intrinsicContentSize: CGSize {
        return CGSize(width: UIViewNoIntrinsicMetric, height: self.intrinsicHeight)
    }
}

class ViewController: UIViewController {
    @IBOutlet weak var textView: UITextView!

    override func viewDidLoad() {
        super.viewDidLoad()

        textView.becomeFirstResponder()

        let inputView = CustomInputView()
        // To make the view's size more clear.
        inputView.backgroundColor = UIColor(red: 0.5, green: 1, blue: 0.5, alpha: 1)
        textView.inputView = inputView

        // To demonstrate a change to the view's intrinsic height.
        DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + .seconds(2)) {
            inputView.intrinsicHeight = 400
        }
    }
}

See also https://stackoverflow.com/a/40359382/153354.