Store MKMapSnapshotter as NSData in memory - Swift
I am trying to take a screenshot of my MKMapView. I usually achieved this using the below code in Objective C.
I am wondering how to store the NSData object in memory rather than store the image and then read it right away.
I'm also wondering how this could be written in Swift - specifically the completion handler . I have looked through the docs - but not sure about the syntax: https://developer.apple.com/library/prerelease/iOS/documentation/MapKit/Reference/MKMapSnapshotter_class/index.html#//apple_ref/c/tdef/MKMapSnapshotCompletionHandler
MKMapSnapshotOptions *options = [[MKMapSnapshotOptions alloc] init];
options.region = self.mapView.region;
options.size = self.mapView.frame.size;
options.scale = [[UIScreen mainScreen] scale];
NSURL *fileURL = [NSURL fileURLWithPath:@"path/to/snapshot.png"];
MKMapSnapshotter *snapshotter = [[MKMapSnapshotter alloc] initWithOptions:options];
[snapshotter startWithCompletionHandler:^(MKMapSnapshot *snapshot, NSError *error) {
if (error) {
NSLog(@"[Error] %@", error);
return;
}
UIImage *image = snapshot.image;
NSData *data = UIImagePNGRepresentation(image);
[data writeToURL:fileURL atomically:YES];
}];
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In terms of "persisting" in memory, you can return NSData
via an Objective-C completion block (or Swift closure). From there you can pass to NSData
another method or store it in a property of the class.
For example, in Objective-C:
/** Request NSData of PNG representation of map snapshot.
*
* @param mapView The MKMapView for which we're capturing the snapshot
* @param completion The completion block that will be called when the asynchronous snapshot is done. This takes two parameters, the resulting NSData upon success and an NSError if there was an error.
*/
- (void)requestSnapshotDataForMapView:(MKMapView *)mapView completion:(void (^)(NSData *data, NSError *error))completion
{
MKMapSnapshotOptions *options = [[MKMapSnapshotOptions alloc] init];
options.region = mapView.region;
options.size = mapView.frame.size;
options.scale = [[UIScreen mainScreen] scale];
MKMapSnapshotter *snapshotter = [[MKMapSnapshotter alloc] initWithOptions:options];
[snapshotter startWithCompletionHandler:^(MKMapSnapshot *snapshot, NSError *error) {
if (error) {
if (completion) {
completion(nil, error);
}
return;
}
UIImage *image = snapshot.image;
NSData *data = UIImagePNGRepresentation(image);
if (completion) {
completion(data, nil);
}
}];
}
- (IBAction)didTouchUpInsideButton:(id)sender
{
[self requestSnapshotDataForMapView:self.mapView completion:^(NSData *data, NSError *error) {
if (error) {
NSLog(@"requestSnapshotDataForMapView error: %@", error);
return;
}
// do whatever you want with the `data` parameter here, for example,
// if you had some `@property (nonatomic, strong) NSData *snapshotData;`,
// you might do:
//
// self.snapshotData = data
// now initiate the next step of the process in which you're presumably
// going to use the `data` provided by this block.
}];
}
Swift equivalent:
/// Request NSData of PNG representation of map snapshot.
///
/// - parameter mapView: The MKMapView for which we're capturing the snapshot
/// - parameter completion: The closure that will be called when the asynchronous snapshot is done. This takes two parameters, the resulting NSData upon success and an NSError if there was an error.
func requestSnapshotData(mapView: MKMapView, completion: (NSData?, NSError?) -> ()) {
let options = MKMapSnapshotOptions()
options.region = mapView.region
options.size = mapView.frame.size
options.scale = UIScreen.mainScreen().scale
let snapshotter = MKMapSnapshotter(options: options)
snapshotter.startWithCompletionHandler() { snapshot, error in
guard snapshot != nil else {
completion(nil, error)
return
}
let image = snapshot!.image
let data = UIImagePNGRepresentation(image)
completion(data, nil)
}
}
@IBAction func didTouchUpInsideButton(sender: AnyObject) {
requestSnapshotData(mapView) { data, error in
guard data != nil else {
print("requestSnapshotData error: \(error)")
return
}
// do whatever you want with the `data` parameter here, for example,
// if you had some `var snapshotData: NSData?` class property, you might do:
//
// self.snapshotData = data
// now initiate the next step of the process in which you're presumably
// going to use the `data` provided by this closure.
}
}
Honestly, if you are trying to use UIImage
somewhere else, I can change these lock / close options to use UIImage
instead NSData
, but hopefully this illustrates the idea.
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