如何定期更新 Mapview？

Question

在我的应用程序中，我想定期更新 MapView 并根据新位置重绘地图上的路径。 是否可以使用 MKMapView？

这是我在 mapview 上绘制和注释的方法。

- (void)viewDidLoad
 {

NSString *url=[NSString stringWithFormat:@"xxxxx.php?uid=%@&buddy_uid=%@",UserUID,buddyUid];
NSLog(@"%@",url);
NSLog(@"%@",url);
NSString * jsonString = [[NSString alloc] initWithContentsOfURL:[NSURL URLWithString:url] encoding:NSUTF8StringEncoding error:nil];
NSLog(@"return data %@",jsonString);
NSDictionary *jsonDic = [jsonString JSONValue];
buddyLocation = [[NSString alloc] initWithFormat:@"%@,%@",[jsonDic objectForKey:@"Lattitude"],[jsonDic objectForKey:@"Longitude"]];

[super viewDidLoad];

locmanager = [[CLLocationManager alloc] init]; 
[locmanager setDelegate:self]; 
[locmanager setDesiredAccuracy:kCLLocationAccuracyBest];
//[locmanager startUpdatingLocation];
MKMapView *mapnew;
if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad)
{
    mapnew = [[MKMapView alloc] initWithFrame:CGRectMake(0, 0, 768, 1004)];
}
else
{
    mapnew = [[MKMapView alloc] initWithFrame:CGRectMake(0, 0, 320, 460)];
}

[mapnew setDelegate:self];
[self.view addSubview:mapnew];

MKCoordinateRegion region = { {0.0, 0.0 }, { 0.0, 0.0 } }; 
region.center.latitude = lat1 floatValue];//22.56574;
region.center.longitude =lng1 floatValue];//73.74575;
NSString *currentLocation = [[NSString alloc] initWithFormat:@"%@,%@",lat1,lng1];
NSLog(@"%@",currentLocation);

DisplayMap *ann = [[DisplayMap alloc] init]; 
ann.title = @"Current Location";
ann.coordinate = region.center; 
[mapnew addAnnotation:ann];

NSLog(@"%@",jsonDic);
region.center.latitude = [[jsonDic objectForKey:@"Lattitude"] floatValue];//23.56574;
region.center.longitude = [[jsonDic objectForKey:@"Longitude"] floatValue];//72.74575;

ann = [[DisplayMap alloc] init]; 
ann.title = @"Buddy Location";
ann.coordinate = region.center; 

    [mapnew addAnnotation:ann];
    KMLParser *kml = [KMLParser parseKMLAtURL:[NSURL URLWithString:[NSString 
    stringWithFormat:@"https://maps.google.com/maps?saddr=%@&daddr=%@&
    output=kml",currentLocation,buddyLocation]]]; 
    NSArray *overlays = [kml overlays];
    [mapnew addOverlays:overlays];

    MKMapRect flyTo = MKMapRectNull;
    for (id <MKOverlay> overlay in overlays) 
    {
        if (MKMapRectIsNull(flyTo)) 
        {
            flyTo = [overlay boundingMapRect];
        }
        else 
        {
            flyTo = MKMapRectUnion(flyTo, [overlay boundingMapRect]);
        }
    }

    mapnew.visibleMapRect = flyTo;
    [mapnew release];
    mapnew =nil;
}

 }
 -(MKOverlayView *)mapView:(MKMapView *)mapView viewForOverlay:(id <MKOverlay>)overlay 
 {        
MKPolylineView *line = [[[MKPolylineView alloc] initWithPolyline:overlay] autorelease]; 
line.strokeColor = [UIColor blueColor]; 
line.lineWidth =2.0;
return line;
 }

Answer 1

ViewDidiLoad 方法仅在视图加载时调用一次，之后它只会在连续访问时将控制权交给 viewWillappear 等方法。您需要做的是将解析位置数据的方法与 viewDidLoad 分开，并使其设置一个数组或对象。并调用该方法在 Map 上重置这些内容，即删除以前的注释或覆盖，然后添加新的。问题解决了。您可以使用计时器或类似的东西以固定的时间间隔调用这些方法。我想这应该会有所帮助。