MKMapRect zooms too much - iphone

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

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 2

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];

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

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 5

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];