可以拖动的View

定义一个继承自UIview的类（即我们要移动的视图）

BallView.h

@interface BallView : UIView
{
    CGPoint startPoint;
}
@end

BallView.m

@implementation BallView

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
    // 获取触摸对象
    UITouch *touch = [touches anyObject];
    startPoint = [touch locationInView:self];
}

- (void)touchesMoved:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
    //获取触摸的对象
    UITouch *touch = [touches anyObject];
    CGPoint newPoint = [touch locationInView:self];
    // 分别计算x y变动的距离
    CGFloat dx = newPoint.x - startPoint.x;
    CGFloat dy = newPoint.y - startPoint.y;
    
    // 改变中心点坐标
    self.center = CGPointMake(self.center.x + dx, self.center.y + dy);
}

@end

接下来我们在根视图控制器中引入头文件，初始化加入视图即可

- (void)viewDidLoad {
    [super viewDidLoad];
    
    BallView *ball = [[BallView alloc] initWithFrame:CGRectMake(0, 0, 100, 100)];
    ball.backgroundColor = [UIColor redColor];
    ball.layer.cornerRadius = ball.frame.size.width / 2;
    ball.layer.masksToBounds = YES;
    [self.view addSubview:ball];
}