Question

For a exercise I created a project to experiment with the accelerometer functions of the iPhone. Right now when I run the app on my device it begins with a blank screen, shake the phone and a image is displayed.

I have to force close the app to clear the image. I was hoping someone could provide a solution that would make the image reset so I could repeat the process as many times as I wanted. (shake phone, display image, clear image) I’m thinking it needs a timer or something, not sure. Here is the source code. Thanks for taking the time to read and help.

//  ViewController.m
//  AccelTest
//


#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

}

- (void)viewDidUnload
{
    [super viewDidUnload];
}

-(void)viewWillAppear:(BOOL)animated{
    [self startAccel];
    [self view];

}

-(void)viewWillDisappear:(BOOL)animated{
    [self stopAccel];
    [self view];
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    return NO;
}


-(void)accelerometer:(UIAccelerometer *)accelerometer didAccelerate:(UIAcceleration *)acceleration{

    double const kThreshold = 2.0;
//    double const kThreshold = 2.0;
    if ( fabsf(acceleration.x) > kThreshold
        || fabsf(acceleration.y) > kThreshold
        || fabsf(acceleration.z) > kThreshold){


        [self.view addSubview:[[UIImageView alloc]initWithImage:[UIImage imageNamed:@"Icon.png"]]];

    }
}


-(void)startAccel{
    UIAccelerometer * accel = [UIAccelerometer sharedAccelerometer];
    accel.delegate = self;
    accel.updateInterval = .25;
}

-(void)stopAccel{
    UIAccelerometer * accel = [UIAccelerometer sharedAccelerometer];
    accel.delegate = nil;
}


@end

Answer 1

Here is how I would do it (without ARC) to tap the image to make it disappear.

Remove your line:

[self.view addSubview:[[UIImageView alloc]initWithImage:[UIImage imageNamed:@"Icon.png"]]];

And add these lines instead:

UIImageView *myImageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"Icon.png"]];
myImageView.userInteractionEnabled = YES;
UITapGestureRecognizer *tapgr = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(rm:)];
[myImageView addGestureRecognizer:tapgr];
[tapgr release]; tapgr = nil;
[self.view addSubview:myImageView];  
[myImageView release]; myImageView = nil;

Then add a method to the View Controller to remove the UIImageView when it is tapped.

-(void)rm:(UITapGestureRecognizer *)tapgr {
    [tapgr.view removeFromSuperview];
}

When that Image is tapped once, the rm: method will be called which will remove the Image from self.view