How to implement the background change viewpoint when the user is moving the iOS device?

Question

As you may know that the iOS 7 home screen can do a visual things like, when the user moving the device, the background is moving as well. How can I do the similar thing in my application? Let say I got two images view. One is on top of another. How to implement the similar things? Thank.

Answer 1

you can set UIInterpolatingMotionEffect x and y ordination with help of UIMotionEffectGroup. I just test one code in to my demo and i put this here check this:-

- (void)viewDidLoad
{
        [super viewDidLoad];
        CGRect frame = self.view.bounds;
        for (NSInteger i=0; i<1; i++) {
            CGFloat left = (frame.size.width-100)/2+i%2*10;
            CGFloat top = (frame.size.height-100)/2+i%3*10;
            UIImageView *demoView = [[UIImageView alloc] initWithFrame:CGRectMake(left, top , 100, 100)];

            [demoView setImage:[UIImage imageNamed:@"FA4nH.jpg"]];

           // demoView.backgroundColor = [UIColor colorWithRed:i/12.0f green:i/18.0f blue:i/24.0f alpha:0.8];
            [self.view addSubview:demoView];
            UIInterpolatingMotionEffect *xAxis = [[UIInterpolatingMotionEffect alloc] initWithKeyPath:@"center.x" type:UIInterpolatingMotionEffectTypeTiltAlongHorizontalAxis];
            UIInterpolatingMotionEffect *yAxis = [[UIInterpolatingMotionEffect alloc] initWithKeyPath:@"center.y" type:UIInterpolatingMotionEffectTypeTiltAlongVerticalAxis];

            left += i*50;
            top += i *50;
            xAxis.minimumRelativeValue = @(-left);
            xAxis.maximumRelativeValue = @(left);
            yAxis.minimumRelativeValue = @(-top);
            yAxis.maximumRelativeValue = @(top);
            UIMotionEffectGroup *motionEffectGroup = [[UIMotionEffectGroup alloc] init];
            motionEffectGroup.motionEffects = @[xAxis, yAxis];
            [demoView addMotionEffect:motionEffectGroup];
        }

}

Check this in to real Device that work nice i tested this in to my one of the demo project. hope that helps to you.

Answer 2

in iOS 7 you have UIMotionEffect.

Another user in Stackoverflow ask a similar question. You can read here: Solution to parallax effect in iOS 7

Also you can take a look to this library in GitHub: NGAParallaxMotion. Basically is a tiny category that help you to achieve a parallax effect with UIMotionEffect.