ios - 在 MKMapview 上移动 MKCircle 并拖动 MKMapview

Question

我在 MKMapView 上有一个 MKCircle。它是用户可拖动的，但如果用户拖动圆圈外的区域， map 应该会移动。

- (IBAction)createPanGestureRecognizer:(id)sender
{
    _mapView.scrollEnabled=NO;
    _panRecognizer = [[UIPanGestureRecognizer alloc]
                      initWithTarget:self action:@selector(respondToPanGesture:)];
    [_mapView addGestureRecognizer:_panRecognizer];
}

-(void)respondToPanGesture:(UIPanGestureRecognizer*)sender {

    static CGPoint originalPoint;

    if (sender.state == UIGestureRecognizerStateBegan) {
        CGPoint point = [sender locationInView:_mapView];
        CLLocationCoordinate2D tapCoordinate = [_mapView convertPoint:point toCoordinateFromView:_mapView];

        CLLocation *tapLocation = [[CLLocation alloc] initWithLatitude:tapCoordinate.latitude longitude:tapCoordinate.longitude];

        CLLocationCoordinate2D originalCoordinate = [_circle coordinate];
        CLLocation *originalLocation = [[CLLocation alloc] initWithLatitude:originalCoordinate.latitude longitude:originalCoordinate.longitude];

        if ([tapLocation distanceFromLocation:originalLocation] > [_circle radius]) {
            _mapView.scrollEnabled=YES;
            _isAllowedToMove=NO;
        }
        else if ([tapLocation distanceFromLocation:originalLocation] < [_circle radius]) {
            originalPoint = [_mapView convertCoordinate:originalCoordinate toPointToView:sender.view];
            _isAllowedToMove=YES;
        }
    }

    if (sender.state == UIGestureRecognizerStateChanged) {
        if (_isAllowedToMove)
        {
            CGPoint translation = [sender translationInView:sender.view];
            CGPoint newPoint    = CGPointMake(originalPoint.x + translation.x, originalPoint.y + translation.y);

            CLLocationCoordinate2D newCoordinate = [_mapView convertPoint:newPoint toCoordinateFromView:sender.view];

            MKCircle *circle2 = [MKCircle circleWithCenterCoordinate:newCoordinate radius:[_circle radius]];
            [_mapView addOverlay:circle2];
            [_mapView removeOverlay:_circle];
            _circle = circle2;
        }
    }

    if (sender.state == UIGestureRecognizerStateEnded || sender.state == UIGestureRecognizerStateFailed || sender.state == UIGestureRecognizerStateCancelled) {
        _mapView.scrollEnabled=NO;
        _isAllowedToMove=NO;
    }
}

拖动圆圈效果很好，但是当尝试拖动 map 时，它会保持静止。我的假设是

_mapView.scrollEnabled=YES;

使 map 可拖动，但需要另一个拖动手势才能启动。如何在不失去移动圆圈能力的情况下实现这一点？

Answer 1

如果用户开始在圆圈外拖动 map ，则可以拖动 map (如果用户开始在圆圈内拖动，则不拖动 map )，不要从一开始就禁用 scrollEnabled -- 让它保持打开状态(直到拖动开始，我们可以决定是否禁用)。

为了让 scrollEnabled 保持开启状态(即让 map 自己平移)和添加我们自己的手势识别器，我们需要实现 shouldRecognizeSimultaneouslyWithGestureRecognizer 并返回 YES。

更新后的 createPanGestureRecognizer: 看起来像这样:

- (IBAction)createPanGestureRecognizer:(id)sender
{
    //_mapView.scrollEnabled=NO;  // <-- do NOT disable scrolling here
    _panRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(respondToPanGesture:)];
    _panRecognizer.delegate = self;  // <-- to implement shouldRecognize
    [_mapView addGestureRecognizer:_panRecognizer];
}

-(BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
    return YES;
}

然后在我们的手势处理程序中，当手势开始时，根据平移开始的位置(圆圈外或圆圈内)启用或禁用scrollEnabled:

if ([tapLocation distanceFromLocation:originalLocation] > [_circle radius]) {
    _mapView.scrollEnabled=YES;
    _isAllowedToMove=NO;
}
else //if ([tapLocation distanceFromLocation:originalLocation] < [_circle radius]) {
//NOTE: It's not really necessary to check if distance is less than radius
//      in the ELSE part since in the IF we checked if it's greater-than.
//      If we get to the ELSE, we know distance is <= radius.
//      Unless for some reason you want to handle the case where
//      distance exactly equals radius differently but this is unlikely.
{
    originalPoint = [_mapView convertCoordinate:originalCoordinate toPointToView:sender.view];
    _mapView.scrollEnabled=NO;  // <-- disable scrolling HERE
    _isAllowedToMove=YES;
}

最后，在手势结束时始终重新启用 scrollEnabled(以防万一)。
当下一个手势开始时，如有必要，它将被重新禁用:

if (sender.state == UIGestureRecognizerStateEnded || sender.state == UIGestureRecognizerStateFailed || sender.state == UIGestureRecognizerStateCancelled) {
    _mapView.scrollEnabled=YES;  // <-- enable instead of disable
    _isAllowedToMove=NO;
}

请注意，如果允许用户多次调用 createPanGestureRecognizer:，您应该将识别器的创建和添加移动到其他地方(可能是 viewDidLoad)，否则会多次实例将被添加到 map 中。

或者，将按钮更改为切换按钮，以便在“移动”模式打开时从 map 中删除手势识别器，而不是创建和添加它。