Animate the size and layout of UIViews within a UIScrollview. This shows how to use Masonry/AutoLayout to have a UIScrollView with subviews in its content view that can dynamically change their size/layout

MASExampleScrollViewDynamicContentViewSize

//
//  Created by Julian Bleecker on June 22, 2014.
//  Copyright (c) 2014 Julian Bleecker. All rights reserved.
//

#import "MASExampleScrollViewDynamicContentViewSize.h"

/**
 *
 * This shows how to use Masonry/AutoLayout to have a UIScrollView with
 * subviews in its content view that can dynamically change their size/layout
 *
 *
 */

@interface MASExampleScrollViewDynamicContentViewSize () <UIViewControllerAnimatedTransitioning, UIGestureRecognizerDelegate>
@property (strong, nonatomic) UIScrollView* scrollView;
@property (strong, nonatomic) UIView *view_1, *view_2, *view_3, *view_4;
@property CGFloat growingViewHeight;
@property int lowGrowHeight;
@property (nonatomic, strong) UIPercentDrivenInteractiveTransition* inter;
@property BOOL interacting;

@end

@implementation MASExampleScrollViewDynamicContentViewSize

UIView *contentView, *sizingView;
BOOL growUp, lowGrow;
int lowGrowHeight;
CGFloat moveLeft;
UIScreenEdgePanGestureRecognizer *sep;

- (id)init {
    self = [super init];
    if (!self) return nil;
    growUp = YES;
    lowGrow = NO;
    self.growingViewHeight = 50;
    lowGrowHeight = 50;
    UIScrollView *scrollView = UIScrollView.new;
    [scrollView setAutoresizesSubviews:YES];
    self.scrollView = scrollView;
    
    scrollView.backgroundColor = [UIColor lightGrayColor];
    [self addSubview:scrollView];
    [self.scrollView mas_makeConstraints:^(MASConstraintMaker *make) {
        make.edges.equalTo(self);
    }];
    
    // We create a dummy contentView that will hold everything (necessary to use scrollRectToVisible later)
    contentView = UIView.new;
    [self.scrollView addSubview:contentView];
    [contentView mas_makeConstraints:^(MASConstraintMaker *make) {
        make.edges.equalTo(self.scrollView).with.insets(UIEdgeInsetsMake(0, 0, 0, 0));
        make.width.equalTo(self.scrollView.mas_width);
    }];
    
    UIView *lastView;
    
    self.view_1 = UIView.new;
    self.view_1.backgroundColor = [self randomColor];
    self.view_2 = UIView.new;
    self.view_2.backgroundColor = [self randomColor];
    self.view_3 = UIView.new;
    self.view_3.backgroundColor = [self randomColor];
    self.view_4 = UIView.new;
    self.view_4.backgroundColor = [UIColor redColor];
    
    [contentView addSubview:self.view_1];
    [contentView addSubview:self.view_2];
    [contentView addSubview:self.view_3];
    [contentView addSubview:self.view_4];
    
    
    UITapGestureRecognizer *singleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(singleTap:)];
    [self.view_1 addGestureRecognizer:singleTap];
    [self.view_1 mas_updateConstraints:^(MASConstraintMaker *make) {
        make.top.equalTo(@0);
        make.left.equalTo(@0);
        make.width.equalTo(contentView.mas_width);
        make.height.equalTo(@(200));
    }];
    
    UITapGestureRecognizer *singleTap_2 = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(singleTap:)];
    
    [self.view_2 addGestureRecognizer:singleTap_2];
    [self.view_2 mas_updateConstraints:^(MASConstraintMaker *make) {
        make.top.equalTo(self.view_1.mas_bottom);
        make.left.equalTo(@0);
        make.width.equalTo(contentView.mas_width);
        make.height.equalTo(@(100)).key(@"height view_2");
    }];
    
    UIPanGestureRecognizer *flick = [[UIPanGestureRecognizer alloc]initWithTarget:self action:@selector(pan:)];
    flick.delegate = self;
    [self.view_3 addGestureRecognizer:flick];
    [self.view_3 mas_updateConstraints:^(MASConstraintMaker *make) {
        make.top.equalTo(self.view_2.mas_bottom);
        make.left.equalTo(@0);
        make.width.equalTo(contentView.mas_width);
        make.height.equalTo(@(200)).key(@"height view_3");
    }];
    
    
    sep = [[UIScreenEdgePanGestureRecognizer alloc] initWithTarget:self action:@selector(panEdge:)];
    sep.edges = UIRectEdgeRight;
    sep.delegate = self;
    
    [self.view_4 addGestureRecognizer:sep];
    [self.view_4 mas_updateConstraints:^(MASConstraintMaker *make) {
        make.top.equalTo(self.view_3.mas_bottom);
        make.left.equalTo(@0);
        make.width.equalTo(contentView.mas_width);
        make.height.equalTo(@(200)).key(@"height view_4");
        make.bottom.equalTo(contentView.mas_bottom);
    }];
    
    
    lastView = self.view_4;
    
    // dummy view, which determines the size of the contentView size and therefore the scrollView contentSize
    sizingView = UIView.new;
    [sizingView setBackgroundColor:[UIColor purpleColor]];
    [scrollView addSubview:sizingView];
    [sizingView mas_makeConstraints:^(MASConstraintMaker *make) {
        make.top.equalTo(lastView.mas_bottom);
        make.bottom.equalTo(contentView.mas_bottom);
    }];
    [self setNeedsUpdateConstraints];
    
    return self;
}

- (void)updateConstraints {
    
    [self.view_1 mas_updateConstraints:^(MASConstraintMaker *make) {
        make.height.equalTo(@(self.growingViewHeight));
    }];
    
    [self.view_2 mas_updateConstraints:^(MASConstraintMaker *make) {
        make.top.equalTo(self.view_1.mas_bottom);
        make.height.equalTo(@(self.growingViewHeight*1.5));
    }];
    
    [self.view_3 mas_updateConstraints:^(MASConstraintMaker *make) {
        make.top.equalTo(self.view_2.mas_bottom);
        
    }];
    
    [self.view_4 mas_updateConstraints:^(MASConstraintMaker *make) {
        make.top.equalTo(self.view_3.mas_bottom);
        
    }];
    
    [self.view_3 mas_updateConstraints:^(MASConstraintMaker *make) {
        make.height.equalTo(@(lowGrowHeight));
        //make.height.equalTo(self.view_3).with.offset(lowGrowHeight);
    }];
    
    [self.view_4 mas_updateConstraints:^(MASConstraintMaker *make) {
        make.left.equalTo(@(-1*moveLeft));
    }];
    
    //according to apple super should be called at end of method
    [super updateConstraints];
    
}


- (void)panEdge:(UIScreenEdgePanGestureRecognizer *)sender
{
    UIView *v = sender.view;
    if (sender.state == UIGestureRecognizerStateBegan) {
        NSLog(@"%@", @"begin");
        self.inter = [UIPercentDrivenInteractiveTransition new];
        self.interacting = YES;
    }
    else if (sender.state == UIGestureRecognizerStateChanged) {
        CGPoint delta = [sender translationInView: v];
        CGFloat percent = fabs(delta.x/v.bounds.size.width);
        [self.inter updateInteractiveTransition:percent];
        NSLog(@"%f", percent);
        moveLeft = 300*percent;
    }
    else if (sender.state == UIGestureRecognizerStateEnded) {
        CGPoint delta = [sender translationInView: v];
        CGFloat percent = fabs(delta.x/v.bounds.size.width);
        self.inter.completionSpeed = 0.5;
        // (try completionSpeed = 2 to see "ghosting" problem after a partial)
        // (can occur with 1 as well)
        // (setting to 0.5 seems to fix it)
        
        if (percent > 0.5) {
            NSLog(@"%@", @"calling finish");
            [self.inter finishInteractiveTransition];
            moveLeft = 0;
        }
        else {
            NSLog(@"%@", @"calling cancel");
            [self.inter cancelInteractiveTransition];
            moveLeft = 0;
        }
    }
    else if (sender.state == UIGestureRecognizerStateCancelled) {
        [self.inter cancelInteractiveTransition];
    }
    
    
    [self setNeedsUpdateConstraints];
    
    // update constraints now so we can animate the change
    [self updateConstraintsIfNeeded];
    
    [UIView animateWithDuration:0.1 animations:^{
        [self layoutIfNeeded];
    }];
    
}

- (void)pan:(UIPanGestureRecognizer *)sender
{
    
    if(sender.view == self.view_3) {
        CGPoint velocity = [sender velocityInView:sender.view];
        if(sender.state == UIGestureRecognizerStateEnded) {
            
            if (velocity.y >0)   // panning down
            {
                lowGrow = YES;
                lowGrowHeight += 50;
                [sender.view setBackgroundColor:[self randomColor]];
                
                //self.brightness = self.brightness -.02;
            }
            if (velocity.y <0)                // panning up
            {
                lowGrow = NO;
                lowGrowHeight -= 50;
                //self.brightness = self.brightness +.02;
                NSLog (@"Increasing brigntness in pan");
            }
            if(lowGrowHeight < 50) lowGrowHeight = 50;
        }
        
        //    if(sender.state == UIGestureRecognizerStateBegan) {
        //        lowGrow ^= YES;
        //    }
        [self setNeedsUpdateConstraints];
        
        // update constraints now so we can animate the change
        [self updateConstraintsIfNeeded];
        
        [UIView animateWithDuration:0.2 animations:^{
            [self layoutIfNeeded];
        }];
    }
    
}

- (BOOL)gestureRecognizerShouldBegin:(UIPanGestureRecognizer *)gestureRecognizer
{
    if(gestureRecognizer == sep) {
        return YES;
    }
    if(gestureRecognizer.view == self.view_3) {
        CGPoint translation = [gestureRecognizer locationInView:self.view_3];
        if(translation.x <50) {
            return YES;
        }
    }
    return NO;
}

- (void)singleTap:(UITapGestureRecognizer*)sender {
    //[sender.view setAlpha:sender.view.alpha / 1.20]; // To see something happen on screen when you tap :O
    UIView *view = sender.view;
    if(view == self.view_1) {
        
        if (growUp == YES) {
            self.growingViewHeight += 250;
            growUp = NO;
        } else {
            self.growingViewHeight -= 250;
            growUp = YES;
        }
    }
    
    
    //self.view_2.frame = CGRectMake(0, 0, 300, 300);
    //view.frame = CGRectMake(view.frame.origin.x, view.frame.origin.y, view.frame.size.width, self.growingViewHeight);
    [self setNeedsUpdateConstraints];
    
    // update constraints now so we can animate the change
    [self updateConstraintsIfNeeded];
    
    [UIView animateWithDuration:0.4 animations:^{
        [self layoutIfNeeded];
    }];
    
    
    [self.scrollView scrollRectToVisible:sender.view.frame animated:YES];
}

-(NSTimeInterval)transitionDuration:(id<UIViewControllerContextTransitioning>)transitionContext {
    return 0.4;
}

-(void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext {
    NSLog(@"%@", transitionContext);
}

- (UIColor *)randomColor {
    CGFloat hue = ( arc4random() % 256 / 256.0 );  //  0.0 to 1.0
    CGFloat saturation = ( arc4random() % 128 / 256.0 ) + 0.5;  //  0.5 to 1.0, away from white
    CGFloat brightness = ( arc4random() % 128 / 256.0 ) + 0.5;  //  0.5 to 1.0, away from black
    return [UIColor colorWithHue:hue saturation:saturation brightness:brightness alpha:1];
}

@end