MKMapRect zooms too much

Question

I use this code to show all my annotations on my map:

 MKMapRect zoomRect = MKMapRectNull;
        for (id <MKAnnotation> annotation in mapView.annotations)
        {
            MKMapPoint annotationPoint = MKMapPointForCoordinate(annotation.coordinate);
            MKMapRect pointRect = MKMapRectMake(annotationPoint.x, annotationPoint.y, 0, 1000);
            if (MKMapRectIsNull(zoomRect)) {
                zoomRect = pointRect;
            } else {
                zoomRect = MKMapRectUnion(zoomRect, pointRect);
            }
        }
        [mapView setVisibleMapRect:zoomRect animated:YES];

But my problem is that when the annotations are close to each other, it zooms too much as the rectangle is small.

Any way to fix this?

Answer 1

For those of us who like one liners:

let minRectSize: Double = 5000
zoomRect = MKMapRect(
    x: zoomRect.minX - max(0, minRectSize - zoomRect.width) / 2,
    y: zoomRect.minY - max(0, minRectSize - zoomRect.height) / 2,
    width: max(zoomRect.width, minRectSize),
    height: max(zoomRect.height, minRectSize))

Answer 2

In my code, I add extra spacing around, so it will automatically adjust the zoom level in order to fit.

[aMapView setVisibleMapRect:zoomRect edgePadding:UIEdgeInsetsMake(-100, -50, -50, -50) animated:YES];

Answer 3

Ariel's solution wasn't working for me either but n00neimp0rtant's was. I have rewritten it in Swift as a function rectWithMinimumZoom(_ minimumZoom: Double) in an extension of MKMapRect. In return it the adjusted rect (if adjustment is needed). Also I added a extra safety that minimumZoom cannot be divided by 0.

SWIFT

extension MKMapRect {
func rectWithMinimumZoom(_ minimumZoom: Double = 750) -> MKMapRect{
    var needChange = false

    var x = MKMapRectGetMinX(self)
    var y = MKMapRectGetMinY(self)
    var w = MKMapRectGetWidth(self)
    var h = MKMapRectGetHeight(self)
    let centerX = MKMapRectGetMidX(self)
    let centerY = MKMapRectGetMidY(self)

    if(h < minimumZoom){
        let factor = minimumZoom / max(h,1)
        h = minimumZoom
        w *= factor;
        x = centerX - w / 2
        y = centerY - h / 2
        needChange = true
    }
    if(w < minimumZoom){
        let factor = minimumZoom / max(w,1)
        w = minimumZoom
        h *= factor
        x = centerX - w / 2
        y = centerY - h / 2
        needChange = true
    }
    if(needChange){
        return MKMapRectMake(x, y, w, h);
    }
    return self
}

Answer 4

Try this code:

//here comes your for loop...

double minMapHeight = 10; //choose some value that fit your needs
double minMapWidth = 10;  //the same as above
BOOL needChange = NO;

double x = MKMapRectGetMinX(zoomRect);
double y = MKMapRectGetMinY(zoomRect);
double w = MKMapRectGetWidth(zoomRect);
double h = MKMapRectGetHeight(zoomRect);  //here was an error!!

if(MKMapRectGetHeight(zoomRect) < minMapHeight){
    x -= minMapWidth/2;
    w += minMapWidth/2;
    needChange = YES;
}
if(MKMapRectGetWidth(zoomRect) < minMapWidth){
    y -= minMapHeight/2;
    h += minMapHeight/2;
    needChange = YES;
}
if(needChange){
    zoomRect = MKMapRectMake(x, y, w, h);
}
[mapView setVisibleMapRect:zoomRect animated:YES];

EDITED ->

double minMapHeight = 250; //choose some value that fit your needs
double minMapWidth = 250;  //the same as above
BOOL needChange = NO;

double x = MKMapRectGetMinX(zoomRect);
double y = MKMapRectGetMinY(zoomRect);
double w = MKMapRectGetWidth(zoomRect);
double h = MKMapRectGetHeight(zoomRect);
double centerX = MKMapRectGetMidX(zoomRect);
double centerY = MKMapRectGetMidY(zoomRect);

if(MKMapRectGetHeight(zoomRect) < minMapHeight){
    //x -= minMapWidth/2;
    //w += minMapWidth/2;
    x = centerX - w/2;
    needChange = YES;
}
if(MKMapRectGetWidth(zoomRect) < minMapWidth){
    //y -= minMapHeight/2;
    //h += minMapHeight/2;
    y = centerY - h/2;
    needChange = YES;
}
if(needChange){
    zoomRect = MKMapRectMake(x, y, w, h);
}
[mapView setVisibleMapRect:zoomRect animated:YES];

Answer 5

Ariel's answer didn't work for me, but I made a few small changes to it and it's working great now (especially with maps with a single pin):

double minimumZoom = 6000; // for my purposes the width/height have same min zoom
BOOL needChange = NO;

double x = MKMapRectGetMinX(zoomRect);
double y = MKMapRectGetMinY(zoomRect);
double w = MKMapRectGetWidth(zoomRect);
double h = MKMapRectGetHeight(zoomRect);
double centerX = MKMapRectGetMidX(zoomRect);
double centerY = MKMapRectGetMidY(zoomRect);

if (h < minimumZoom) {  // no need to call MKMapRectGetHeight again; we just got its value!
    // get the multiplicative factor used to scale old height to new,
    // then apply it to the old width to get a proportionate new width
    double factor = minimumZoom / h;
    h = minimumZoom;
    w *= factor;
    x = centerX - w/2;
    y = centerY - h/2;
    needChange = YES;
}

if (w < minimumZoom) {
    // since we've already adjusted the width, there's a chance this
    // won't even need to execute
    double factor = minimumZoom / w;
    w = minimumZoom;
    h *= factor;
    x = centerX - w/2;
    y = centerY - h/2;
    needChange = YES;
}

if (needChange) {
    zoomRect = MKMapRectMake(x, y, w, h);
}

[mapView setVisibleMapRect:zoomRect animated:YES];