基于这个答案:

Snapshot of MKMapView

我尝试将我的 map 转换为图片，但应用程序从未进入快照程序 block 。

为什么？

//Get location an then get a Picture of the Map.
CLLocation *userLoc = self.map.userLocation.location; //self.map is a MKMapView;
CLLocationCoordinate2D punto = userLoc.coordinate;
MKCoordinateRegion region = MKCoordinateRegionMakeWithDistance(punto, 500, 500);
[self.map setRegion:(region)];
[self.map setShowsUserLocation:YES];
//Place a Pin in actual location.
MKPointAnnotation *pin = [[MKPointAnnotation alloc]init];
pin.coordinate = punto;
pin.title = @"Localización";
[self.map addAnnotation:pin];

//Convert map to picture.
MKMapSnapshotOptions *options = [[MKMapSnapshotOptions alloc] init];
options.region = self.map.region;
options.scale = [UIScreen mainScreen].scale;
options.size = self.map.frame.size;

MKMapSnapshotter *snapshotter = [[MKMapSnapshotter alloc] initWithOptions:options];
[snapshotter startWithQueue:dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0) completionHandler:^(MKMapSnapshot *snapshot, NSError *error) {
    NSLog(@"Entering the block."); //Never prints!
    // get the image associated with the snapshot
    UIImage *image = snapshot.image;
    NSLog(@"imagen %@",image); //Niether do this!
    // Get the size of the final image
    CGRect finalImageRect = CGRectMake(0, 0, image.size.width, image.size.height);
    // Get a standard annotation view pin. Clearly, Apple assumes that we'll only want to draw standard annotation pins!
    MKAnnotationView *pin = [[MKPinAnnotationView alloc] initWithAnnotation:nil reuseIdentifier:@""];
    UIImage *pinImage = pin.image;
    // ok, let's start to create our final image
    UIGraphicsBeginImageContextWithOptions(image.size, YES, image.scale);
    // first, draw the image from the snapshotter
    [image drawAtPoint:CGPointMake(0, 0)];
    // now, let's iterate through the annotations and draw them, too
    for (id<MKAnnotation>annotation in self.map.annotations)
    {
        CGPoint point = [snapshot pointForCoordinate:annotation.coordinate];
        if (CGRectContainsPoint(finalImageRect, point)) // this is too conservative, but you get the idea
        {
            CGPoint pinCenterOffset = pin.centerOffset;
            point.x -= pin.bounds.size.width / 2.0;
            point.y -= pin.bounds.size.height / 2.0;
            point.x += pinCenterOffset.x;
            point.y += pinCenterOffset.y;
            [pinImage drawAtPoint:point];
        }
    }
    // grab the final image
    UIImage *finalImage = UIGraphicsGetImageFromCurrentImageContext();
    NSLog(@"Picture inside the block %@",finalImage);  //Never prints.
    UIGraphicsEndImageContext();
    // and save it
    NSData *data = UIImagePNGRepresentation(finalImage);
    [data writeToFile:@"Picture.jpg" atomically:YES];
    if (error) {
        NSLog(@"Error"); //This is not printed.
    }else{
        NSLog(@"Success!"); //Neither do this.
        self.fotoParaEnviar = finalImage;
    }
}];
NSLog(@"Picture outside the block %@",self.fotoParaEnviar); //This is allway NULL

看起来一切都很好地实例化了。

那么为什么该 block 永远不会执行？

最佳答案

如果您已经在显示 map ，则无需任何魔法即可将其保存为图像，Snapshot of MKMapView in iOS7几乎正确地得到它，我不明白为什么他们得到黑色图像，但我没有通过 0.0 作为渲染比例，而是 1.0 或 2.0(视网膜)，也许他们的代码不在主线程上，因为它应该用于图形。

无论如何，我刚刚在 7.1 上尝试过这个并获得了带有用户蓝点和注释图钉的正确图像:

[ObCommons createJPEGfromView:self.map withSize:self.map.bounds.size toPath:[ObCommons getPathInDocuments:@"test.jpg"]];

+(UIImage*) createImageFromView:(UIView*)newt withSize:(CGSize)rensize {
    UIGraphicsBeginImageContextWithOptions(rensize, NO, 2.0);   // 1.0 or 2.0 for retina (get it from UIScreen)
    [newt.layer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();    
    UIGraphicsEndImageContext();

    return image;
}

+(UIImage*) createJPEGfromView:(UIView*)newt withSize:(CGSize)rensize toPath:  (NSString*)filePath quality:(float)quality{
    UIImage *ximage = [ObCommons createImageFromView:newt withSize:rensize];    
    NSData *imageData = UIImageJPEGRepresentation(ximage, quality);

    if (filePath!=nil) {
        [imageData writeToFile:filePath atomically:YES];
    }

    return ximage;
}

+(CGFloat)retinaFactor {
    if ([[UIScreen mainScreen] respondsToSelector:@selector(scale)] && [[UIScreen mainScreen] scale] > 1) {
        return [[UIScreen mainScreen]scale];
    } else {
        return 1.0f;
    }
}

为了更具可读性，这里是相关方法的要点:https://gist.github.com/quentar/d92e95728ce0d950db65

关于iOS 将 MKMapView 转换为 UIImage。从不进入街区，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/23569432/