在UITableViewCell中显示MKMapView而不会减慢UI

Question

我正在尝试将MKMapView放在某些UiTableViewCell中，但是（在iPhone 5上，甚至在其他设备上），当应用程序使用地图加载单元格时，滚动变得不太顺畅。

有一些方法，使用GCD或其他方法，以更好的方式做到这一点？

以下是结果的屏幕截图：

我从Nib加载Cell，这里是我设置坐标和注释的代码（使用自定义视图，但这不是问题。）

    // Delegate
    cell.objectMap.delegate = self;

    // Coordinate
    MKCoordinateRegion region;
    region.center = activity.object.location.coordinate;
    MKCoordinateSpan span;
    span.latitudeDelta = 0.055;
    span.longitudeDelta = 0.055;
    region.span = span;
    [cell.objectMap setRegion:region animated:NO];

    // Add an annotation
    MKPointAnnotation *point = [[MKPointAnnotation alloc] init];
    point.coordinate = activity.object.location.coordinate;
    [cell.objectMap addAnnotation:point];

    // Show the MKMapView in the cell
    cell.objectMap.hidden = NO;

Answer 1

我最终将MKMapSnapshotter用于支持这种强大而快速功能的设备，并使用Google Static Maps Api支持运行iOS6的设备。我认为这是我能得到的最好，最快的解决方案。

感谢@Rob提出建议。

if ( IS_IOS7 ) {

    // Placeholder
    cell.objectImage.image = [UIImage imageNamed:@"mapPlaceholder"];

    // Cooridinate
    MKCoordinateRegion region;
    region.center = activity.object.location.coordinate;
    MKCoordinateSpan span;
    span.latitudeDelta = 0.055;
    span.longitudeDelta = 0.055;
    region.span = span;
    [self.mapViewForScreenshot setRegion:region animated:NO];

    MKMapSnapshotOptions *options = [[MKMapSnapshotOptions alloc] init];
    options.region = self.mapViewForScreenshot.region;
    options.scale = [UIScreen mainScreen].scale;
    options.size = CGSizeMake(300, 168);

    MKMapSnapshotter *snapshotter = [[MKMapSnapshotter alloc] initWithOptions:options];
    [snapshotter startWithCompletionHandler:^(MKMapSnapshot *snapshot, NSError *error) {

        UIImage *image = snapshot.image;
        [cell.objectImage setImage:image];
        cell.mapPinImageView.hidden = NO;

    }];

}else{

    cell.mapPinImageView.hidden = NO;
    [cell.objectImage setImageWithURL:[NSURL URLWithString:[NSString stringWithFormat:@"http://maps.googleapis.com/maps/api/staticmap?center=%f,%f&zoom=14&size=600x338&maptype=roadmap&sensor=false&key=APIKEY",activity.object.location.coordinate.latitude, activity.object.location.coordinate.longitude]] placeholderImage:nil];

}

Answer 2

根据您的回答，您还可以在后台创建快照并在主队列上执行结果（在更新您的单元格之前不要原谅检查错误）：

if ( IS_IOS7 ) {

    cell.objectImage.image = [UIImage imageNamed:@"mapPlaceholder"];

    // Cooridinate
    MKCoordinateRegion region;
    region.center = activity.object.location.coordinate;
    MKCoordinateSpan span;
    span.latitudeDelta = 0.055;
    span.longitudeDelta = 0.055;
    region.span = span;
    [self.mapViewForScreenshot setRegion:region animated:NO];

    MKMapSnapshotOptions *options = [[MKMapSnapshotOptions alloc] init];
    options.region = self.mapViewForScreenshot.region;
    options.scale = [UIScreen mainScreen].scale;
    options.size = CGSizeMake(300, 168);

    MKMapSnapshotter *snapshotter = [[MKMapSnapshotter alloc] initWithOptions:options];

    dispatch_queue_t executeOnBackground = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

    [snapshotter startWithQueue:executeOnBackground completionHandler:^(MKMapSnapshot *snapshot, NSError *error) {

        dispatch_async(dispatch_get_main_queue(), ^{
                if (!error) {
                    cell.objectImage.image = snapshot.image;
                    cell.mapPinImageView.hidden = NO;
                } 
            });
        }];
    }];

} else {
    cell.mapPinImageView.hidden = NO;
    [cell.objectImage setImageWithURL:[NSURL URLWithString:@""] placeholderImage:nil];
}