按钮拖动

@implementation ViewController{
    UIButton* btn;
    CGPoint lastPoint;
}

- (void)viewDidLoad {
    [super viewDidLoad];

    [super viewDidLoad];
    btn = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    [btn setBackgroundColor:[UIColor blackColor]];
    btn.frame = CGRectMake(10, 10, 150, 50);

    [btn setTitle:@"拖动" forState:UIControlStateNormal];

    UIPanGestureRecognizer* movePress = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(dragButton:)];
    [btn addGestureRecognizer:movePress];

    [self.view addSubview:btn];
}

- (void)dragButton:(UILongPressGestureRecognizer *)sender{
    CGPoint point = [sender locationInView:self.view];

    switch (sender.state) {
        case UIGestureRecognizerStateBegan:
            lastPoint = point;
            break;
        case UIGestureRecognizerStateChanged:{
            CGFloat offX = point.x - lastPoint.x;
            CGFloat offY = point.y - lastPoint.y;
            [btn setCenter:CGPointMake(btn.center.x + offX, btn.center.y + offY)];
            lastPoint = point;
        }
            break;
    }
}