iOS:拖动效果不正常

Question

我已经在图像上实现了拖动效果，但是在我的测试中，我看到图像只在单击鼠标事件时移动。

我不能通过拖动事件在屏幕上用鼠标移动图像。但是当我点击屏幕的一侧时，图像就会出现在我点击的地方。

我在youtube上关注了很多话题，但最后，我没有同样的行为。

我的代码:

ScreenView1.h

IBOutlet UIImageView *image;

ScreenView1.m

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{
    UITouch *touch = [[event allTouches] anyObject];
    CGPoint location = [touch locationInView:touch.view];
    image.center = location;
    [self ifCollision];
}
-(void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event{
    [self touchesBegan:touches withEvent:event];
}

Answer 1

如果你想拖拽一个图像视图，你会所以使用UIPanGestureRecognizer会更开心。这让这类事情变得微不足道。使用touchesBegan是如此的iOS 4!

UIPanGestureRecognizer* p =
    [[UIPanGestureRecognizer alloc] initWithTarget:self
                                            action:@selector(dragging:)];
[imageView addGestureRecognizer:p];
// ...
- (void) dragging: (UIPanGestureRecognizer*) p {
    UIView* vv = p.view;
    if (p.state == UIGestureRecognizerStateBegan ||
            p.state == UIGestureRecognizerStateChanged) {
        CGPoint delta = [p translationInView: vv.superview];
        CGPoint c = vv.center;
        c.x += delta.x; c.y += delta.y;
        vv.center = c;
        [p setTranslation: CGPointZero inView: vv.superview];
    }
}

Answer 2

您在touchesMoved:withEvent:中没有做正确的事情，这就是为什么拖拽不起作用。下面是一小段可以工作的代码:

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *touch = [touches anyObject];
    CGPoint location = [touch locationInView:self];
    [CATransaction begin];
    [CATransaction setDisableActions:YES];
    [image setCenter:location];
    [CATransaction commit];
}

Answer 3

对于其他人，我以这种方式实现了我的问题:

- (IBAction)catchPanEvent:(UIPanGestureRecognizer *)recognizer{
    CGPoint translation = [recognizer translationInView:self.view];
    recognizer.view.center = CGPointMake(recognizer.view.center.x + translation.x,
                                         recognizer.view.center.y + translation.y);
    [recognizer setTranslation:CGPointMake(0, 0) inView:self.view];
}

再次感谢你，马特!