MKMapView 在锁定中心时缩放以适应注释

Question

我正在尝试缩放以适应地图上的注释，同时锁定中心并提供一些插图。

- (void)fitAnnotations:(NSArray *)annotations edgeInsets:(UIEdgeInsets)insets
{
    CLLocationCoordinate2D originalCenter = self.centerCoordinate;
    MKMapRect mapRect = MKMapRectNull;

    for (id<MKAnnotation> annotation in annotations) {
        MKMapPoint p = MKMapPointForCoordinate([annotation coordinate]);
        mapRect = MKMapRectUnion(mapRect, MKMapRectMake(p.x, p.y, 0, 0));
    }

    mapRect = [self mapRectThatFits:mapRect edgePadding:insets];
    MKCoordinateRegion mapRegion = MKCoordinateRegionForMapRect(mapRect);

    // we now try to go back to the original center, while increasing the span by neccessary amount
    MKCoordinateSpan centeringDelta = MKCoordinateSpanMake(fabs(mapRegion.center.latitude - originalCenter.latitude), fabs(mapRegion.center.longitude - originalCenter.longitude));
    mapRegion.center = originalCenter;
    mapRegion.span.latitudeDelta += centeringDelta.latitudeDelta * 2.0;
    mapRegion.span.longitudeDelta += centeringDelta.longitudeDelta * 2.0;
    mapRegion = [self regionThatFits:mapRegion];
    [self setRegion:mapRegion animated:YES];
}

此处代码的第一部分按预期工作：它在尊重插图的同时缩放以适应。但是，它会移动中心。

之后我尝试重新调整中心，但失败了。我不确定我关于重新居中的数学是否正确。

Answer 1

计算适合注释的边界图矩形的代码的第一部分是可以的。

只需要校正那个“最小”的地图矩形，使“锁定”的中心实际上在中心。

我认为，主要问题是问题中的代码正在调整跨度，以便在调用 mapRectThatFits: 后重新居中区域并考虑插入（它本身已经给出了稍微修改的版本纠正你实际要求的）。

相反，您的代码应该只计算它想要和然后最终调用setVisibleMapRect:edgePadding:animated:的实际最小矩形，并让地图视图找出“矩形”适合”和插图。

请尝试以下方法：

- (void)fitAnnotations:(NSArray *)annotations edgeInsets:(UIEdgeInsets)insets
{
    MKMapPoint centerMapPoint = MKMapPointForCoordinate(originalCenter);

    //--- First create minimal bounding map rect to tightly fit annotations...
    MKMapRect minimalMapRect = MKMapRectNull;

    for (id<MKAnnotation> annotation in annotations) {
        MKMapPoint annMapPoint = MKMapPointForCoordinate(annotation.coordinate);
        minimalMapRect = MKMapRectUnion(minimalMapRect, MKMapRectMake(annMapPoint.x, annMapPoint.y, 0, 0));
    }


    //--- Now create adjusted map rect so center coordinate is in the center...

    //distance of desired center from minimal left edge...
    double centerXOffset = centerMapPoint.x - minimalMapRect.origin.x;

    //raw amount width needs to be adjusted to get center in center...
    //negative/positive indicates whether center is in left/right half
    double widthOffset = 2.0 * centerXOffset - minimalMapRect.size.width;

    //add absolute value of raw width offset to minimal width...
    double adjustedWidth = minimalMapRect.size.width + fabs(widthOffset);

    //distance of desired center from minimal top edge...
    double centerYOffset = centerMapPoint.y - minimalMapRect.origin.y;

    //raw amount height needs to be adjusted to get center in center...
    //negative/positive indicates whether center is in top/bottom half
    double heightOffset = 2.0 * centerYOffset - minimalMapRect.size.height;

    //add absolute value of raw height offset to minimal height...
    double adjustedHeight = minimalMapRect.size.height + fabs(heightOffset);

    //adjust origin if necessary (if center is in top/left half)...
    MKMapPoint adjustedOrigin = minimalMapRect.origin;
    if ((centerXOffset / minimalMapRect.size.width) < 0.5)
    {
        adjustedOrigin.x = adjustedOrigin.x + widthOffset;
    }
    if ((centerYOffset / minimalMapRect.size.height) < 0.5)
    {
        adjustedOrigin.y = adjustedOrigin.y + heightOffset;
    }

    //create adjusted MKMapRect...
    MKMapRect adjustedMapRect = MKMapRectMake(adjustedOrigin.x, adjustedOrigin.y, adjustedWidth, adjustedHeight);


    //--- Apply the adjusted map rect with insets to map view...
    [mapView setVisibleMapRect:adjustedMapRect edgePadding:insets animated:YES];
}

Answer 2

尝试类似的方法，使用计算出的 mapRect 通过 MKCoordinateRegionMake 方法使用 originalCenter 创建新区域

MKCoordinateRegion mapRegion = MKCoordinateRegionForMapRect(mapRect);
mapRegion = MKCoordinateRegionMake(originalCenter, mapRegion.span);
mapView.region = mapRegion;

Answer 3

试试这个。

MKMapPoint center = MKMapPointForCoordinate(self.mapView.centerCoordinate);

double maxX = 0;
double maxY = 0;
for (MKPointAnnotation *a in self.mapView.annotations)
{
    MKMapPoint p = MKMapPointForCoordinate(a.coordinate);
    double deltaX = fabs(center.x - p.x);
    double deltaY = fabs(center.y - p.y);
    maxX = MAX(maxX, deltaX);
    maxY = MAX(maxY, deltaY);
}


MKMapRect rect = MKMapRectMake(center.x - maxX, center.y - maxY, maxX * 2, maxY * 2);
rect = [self.mapView mapRectThatFits:rect edgePadding:UIEdgeInsetsMake(20, 20, 20, 20)];

[self.mapView setVisibleMapRect:rect animated:1];

Answer 4

@moby 我正在考虑一种不同的方法。像您已经做的那样获取地图中心位置怎么样。现在计算从该中心坐标到每个注释的距离，直到找到最长的注释（比如 'requiredDistance' ）。 使用以下代码获取一个新的地图矩形，其中所有注释都绘制在同一中心：

    MKCircle *circleLine = [MKCircle circleWithCenterCoordinate:self.centerCoordinate radius:requiredDistance];
    [self.mapView setVisibleMapRect:circleLine.boundingMapRect];

来到你的插图，你想要应用的任何插图都应该应用于你的“requiredDistance”变量，这样你的“requiredDistance”变量的值总是大于或等于你的中心坐标和你的中心坐标之间的距离最长的注释，以确保所有注释始终可见。