/*

     File: BasicInterpolationVC.m

 Abstract: View controller that applies interpolation motion effects to

 the position of it's subviews.  A basic parallax effect is created in which a

 view in the foreground appears to float above a recessed background.

 Demonstrates UIInterpolatingMotionEffect and UIMotionEffectGroup.

  Version: 1.0

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#import "BasicInterpolationVC.h"

@interface BasicInterpolationVC ()

@property (nonatomic, weak) IBOutlet UIImageView *backgroundView;

@property (nonatomic, weak) IBOutlet UIView *foregroundView;

@property (nonatomic, weak) IBOutlet UISwitch *foregroundEffectSwitch;

@property (nonatomic, weak) IBOutlet UISwitch *backgroundEffectSwitch;

@property (nonatomic, strong) UIMotionEffectGroup *foregroundMotionEffect;

@property (nonatomic, strong) UIMotionEffectGroup *backgroundMotionEffect;

@property (nonatomic, weak) IBOutlet NSLayoutConstraint *separatorHeightConstraint;

@property (nonatomic, weak) IBOutlet UITextView *textView;

@end

@implementation BasicInterpolationVC

//| ----------------------------------------------------------------------------

- (void)viewDidLoad

{

    [super viewDidLoad];

    self.foregroundView.layer.cornerRadius = 6.0f;

    self.foregroundView.layer.masksToBounds = YES;

    // Create and apply the motion effect for the foreground view.

    {

        UIInterpolatingMotionEffect *xAxis = [[UIInterpolatingMotionEffect alloc] initWithKeyPath:@"center.x" type:UIInterpolatingMotionEffectTypeTiltAlongHorizontalAxis];

        xAxis.minimumRelativeValue = @(-15.0);

        xAxis.maximumRelativeValue = @(15.0);

        UIInterpolatingMotionEffect *yAxis = [[UIInterpolatingMotionEffect alloc] initWithKeyPath:@"center.y" type:UIInterpolatingMotionEffectTypeTiltAlongVerticalAxis];

        yAxis.minimumRelativeValue = @(-15.0);

        yAxis.maximumRelativeValue = @(15.0);

        self.foregroundMotionEffect = [[UIMotionEffectGroup alloc] init];

        self.foregroundMotionEffect.motionEffects = @[xAxis, yAxis];

        [self.foregroundView addMotionEffect:self.foregroundMotionEffect];

    }

    // Create and apply the motion effect for the background view.

    {

        // When configuring a motion effect that effects the position of a

        // view, a positive minimum value combined with a negative maximum

        // value create the illusion of the view being recessed below

        // the screen plane.  For the best looking effect, make sure the

        // view is larger than the bounds of its parent view.

        UIInterpolatingMotionEffect *xAxis = [[UIInterpolatingMotionEffect alloc] initWithKeyPath:@"center.x" type:UIInterpolatingMotionEffectTypeTiltAlongHorizontalAxis];

        xAxis.minimumRelativeValue = @(25.0);

        xAxis.maximumRelativeValue = @(-25.0);

        UIInterpolatingMotionEffect *yAxis = [[UIInterpolatingMotionEffect alloc] initWithKeyPath:@"center.y" type:UIInterpolatingMotionEffectTypeTiltAlongVerticalAxis];

        yAxis.minimumRelativeValue = @(32.0);

        yAxis.maximumRelativeValue = @(-32.0);

        self.backgroundMotionEffect = [[UIMotionEffectGroup alloc] init];

        self.backgroundMotionEffect.motionEffects = @[xAxis, yAxis];

        [self.backgroundView addMotionEffect:self.backgroundMotionEffect];

    }

    [self switchValueChanged:Nil];

    self.separatorHeightConstraint.constant = 0.5;

}

//| ----------------------------------------------------------------------------

- (void)viewDidAppear:(BOOL)animated

{

    [super viewDidAppear:animated];

    [self.textView flashScrollIndicators];

}

//| ----------------------------------------------------------------------------

- (IBAction)switchValueChanged:(id)sender

{

    // Update motion effects on the foregroundView.

    if (self.foregroundEffectSwitch.on &&

        ![self.foregroundView.motionEffects containsObject:self.foregroundMotionEffect])

    {

        [self.foregroundView addMotionEffect:self.foregroundMotionEffect];

    }

    else if (!self.foregroundEffectSwitch.on &&

             [self.foregroundView.motionEffects containsObject:self.foregroundMotionEffect])

    {

        [self.foregroundView removeMotionEffect:self.foregroundMotionEffect];

    }

    // Update motion effects on the backgroundView.

    if (self.backgroundEffectSwitch.on &&

        ![self.backgroundView.motionEffects containsObject:self.backgroundMotionEffect])

    {

        [self.backgroundView addMotionEffect:self.backgroundMotionEffect];

    }

    else if (!self.backgroundEffectSwitch.on &&

             [self.backgroundView.motionEffects containsObject:self.backgroundMotionEffect])

    {

        [self.backgroundView removeMotionEffect:self.backgroundMotionEffect];

    }

}

@end