CODEWITHSUNDEEP
iosobjective-cuiviewautolayoutnslayoutconstraint
vikram17000
vikram17000

Reputation: 453

Auto-layout constraints not getting respected

I am programmatically creating constraints such that the view controller view has a background view and a toolbar, with the toolbar at the bottom. I want the background view's height to decrease as the height of the toolbar increases. After adding the background view and the toolbar as subviews to the view controller's view, I call (in viewDidLoad) the following method that programmatically sets the constraints.

- (void)configureConstraintsForBackgroundViewAndToolbar {

    [self.backgroundView setTranslatesAutoresizingMaskIntoConstraints:NO];
    [self.toolbarComponent setTranslatesAutoresizingMaskIntoConstraints:NO];

    UIView *constraintsBackgroundView = self.backgroundView;
    UIView *constraintsToolbar = self.toolbarComponent;

    NSDictionary *viewsDictionary = NSDictionaryOfVariableBindings(
                                    constraintsBackgroundView, 
                                    constraintsToolbar);
    NSDictionary *metricsDictionary = @{
                                        @"toolbarHeight":[NSNumber numberWithFloat:TOOLBAR_HEIGHT]
                                        };

    [NSLayoutConstraint activateConstraints:
            [NSLayoutConstraint constraintsWithVisualFormat:@"H:|-(0)-[constraintsBackgroundView]-(0)-|" 
            options:NSLayoutFormatDirectionLeadingToTrailing 
            metrics:metricsDictionary 
            views:viewsDictionary]];

    [NSLayoutConstraint activateConstraints:
            [NSLayoutConstraint constraintsWithVisualFormat:@"H:|-(0)-[constraintsToolbar]-(0)-|" 
            options:NSLayoutFormatDirectionLeadingToTrailing 
            metrics:metricsDictionary 
            views:viewsDictionary]];

    [NSLayoutConstraint activateConstraints:
            [NSLayoutConstraint constraintsWithVisualFormat:@"V:|-(0)-[constraintsBackgroundView]-(0)-[constraintsToolbar(>=toolbarHeight)]-(0)-|" 
            options:NSLayoutFormatDirectionLeadingToTrailing 
            metrics:metricsDictionary 
            views:viewsDictionary]];
}

This works fine till the moment I try to update the height of the toolbar using the following method (via an embedded text view). Is there something wrong that I am doing here? The toolbar height increases but the background view does not shorten in height (I debug that using the SparkInspector). Seems pretty straightforward that am missing something obvious here...

- (void)textViewDidChange:(UITextView *)textView {

    if (textView != self.toolbarTextView) {
        return;
    }

    CGFloat currentHeight = self.bounds.size.height;

    CGSize size = [textView sizeThatFits:CGSizeMake(textView.frame.size.width, textView.frame.size.height)];
    CGFloat determinedHeight = fminf(fmaxf(size.height, TOOLBAR_HEIGHT), MAX_TOOLBAR_HEIGHT);

    [self setBounds:CGRectMake(0, 0, self.bounds.size.width, determinedHeight)];    

    [self setNeedsLayout];
}

Also, if I query the toolbar and the background view for their constraints, the constraints between each other that I have set up initially do not come up? They do show only for the view controller's view... that doesn't sound right to me either...?

Many thanks...

Upvotes: 1

Views: 295

Answers (1)

Ishan Handa
Ishan Handa

Reputation: 2281

If you are setting up your layout with constraints it does not make sense to set bounds or frame for your views to update the layout. Instead add constraints in a way that you can edit your layout by changing the constant property of the constraint

For example:

Set height for your toolbar using a specific constraint and store it in a property

NSLayoutConstraint *toolBarHeightConstraint = [NSLayoutConstraint constraintWithItem:constraintsToolbar
                                                                           attribute:NSLayoutAttributeHeight
                                                                           relatedBy:NSLayoutRelationEqual
                                                                              toItem:self.view
                                                                           attribute:NSLayoutAttributeNotAnAttribute
                                                                          multiplier:1
                                                                            constant:TOOLBAR_HEIGHT];

Then change the height of the toolbar by changing the constant for the constraint. like:

toolBarHeightConstraint.constant = newHeight;

In your case you will also need to change your vertical constraint to:

[NSLayoutConstraint activateConstraints:
            [NSLayoutConstraint constraintsWithVisualFormat:@"V:|-(0)-[constraintsBackgroundView]-(0)-[constraintsToolbar]-(0)-|" 
            options:NSLayoutFormatDirectionLeadingToTrailing 
            metrics:metricsDictionary 
            views:viewsDictionary]];

For more information have a look at this answer.

Upvotes: 1

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