Question

当通过模拟器测试地图时，我注意到一些注释显示默认引脚而不是自定义图像。当我回到应用程序主菜单并再次进入mapview时，不同的注释会发生同样的事情。

此代码提供了20个我自己使用相同代码的注释。

-(void)viewDidLoad {

[super viewDidLoad];

_locationManager = [[CLLocationManager alloc] init];
[mapView setDelegate:self];
[mapView setMapType:MKMapTypeStandard];
[mapView setZoomEnabled:YES];
[mapView setScrollEnabled:YES];

MKCoordinateRegion test1 = { {0.0, 0.0} , {0.0, 0.0} };
test1.center.latitude = 55.705609;
test1.center.longitude = 13.195707;
[mapView setRegion:test1 animated:YES];

testmap *ann2 = [[testmap alloc] init];
ann2.title = @"test1";
ann2.subtitle = @"Klicka här för mer info";
ann2.coordinate = test1.center;
ann2.name = @"test1";
[mapView addAnnotation:ann2];

MKCoordinateRegion test2 = { {0.0, 0.0} , {0.0, 0.0} }; //ändra ner
test2.center.latitude = 55.710113;
test2.center.longitude = 13.213500;
[mapView setRegion:test2 animated:YES];

testmap *ann3 = [[testmap alloc] init];
ann3.title = @"test2";
ann3.subtitle = @"Klicka här för mer info";
ann3.coordinate = test2.center;
ann3.name = @"test2";
[mapView addAnnotation:ann3];

MKCoordinateRegion test3 = { {0.0, 0.0} , {0.0, 0.0} };
test3.center.latitude = 55.708981;
test3.center.longitude = 13.197266;
[mapView setRegion:test3 animated:YES];

testmap *ann4 = [[testmap alloc] init];
ann4.title = @"test3";
ann4.subtitle = @"Klicka här för mer info";
ann4.coordinate = test3.center;
ann4.name = @"test3";
[mapView addAnnotation:ann4];

MKCoordinateRegion test4 = { {0.0, 0.0} , {0.0, 0.0} }; //ändra ner
test4.center.latitude = 55.705170;
test4.center.longitude = 13.191277;
[mapView setRegion:test4 animated:YES];

testmap *ann5 = [[testmap alloc] init];
ann5.title = @"test4";
ann5.subtitle = @"Klicka här för mer info";
ann5.coordinate = test4.center;
ann5.name = @"test4";
[mapView addAnnotation:ann5];
}

- (MKAnnotationView *)mapView:(MKMapView *)mapview viewForAnnotation:(id <MKAnnotation>)annotation

{

if ([annotation isKindOfClass:[MKUserLocation class]])
    return nil;
static NSString* AnnotationIdentifier = @"AnnotationIdentifier";
MKAnnotationView *annotationView = [mapView dequeueReusableAnnotationViewWithIdentifier:AnnotationIdentifier];




if(annotationView)
    return nil;
else
{
    MKAnnotationView *annotationView = [[MKAnnotationView alloc] initWithAnnotation:annotation


  reuseIdentifier:AnnotationIdentifier];    annotationView.canShowCallout = YES;
   NSString* thisModelName = ((testmap*)annotation).name;

    if ([thisModelName isEqualToString:@"test1"]) {
    annotationView.image = [UIImage imageNamed:@"test1"];
    UIButton* rightButton = [UIButton buttonWithType:UIButtonTypeDetailDisclosure];

        [rightButton setTitle:annotation.title forState:UIControlStateNormal];
        annotationView.rightCalloutAccessoryView = rightButton;
        annotationView.canShowCallout = YES;
        annotationView.draggable = YES;
        annotationView.highlighted = YES;

    return annotationView;
    }
    else if ([thisModelName isEqualToString:@"test2"])
    {
        annotationView.image = [UIImage imageNamed:@"test2"];
        UIButton* rightButton = [UIButton buttonWithType:UIButtonTypeDetailDisclosure];
        [rightButton addTarget:self action:@selector(myButton:) forControlEvents:UIControlEventTouchUpInside];
        [rightButton setTitle:annotation.title forState:UIControlStateNormal];
        annotationView.rightCalloutAccessoryView = rightButton;
        annotationView.canShowCallout = YES;
        annotationView.draggable = YES;
        annotationView.highlighted = YES;
        return annotationView;
    }
    else if ([thisModelName isEqualToString:@"test3"])
    {
        annotationView.image = [UIImage imageNamed:@"test3"];
        UIButton* rightButton = [UIButton buttonWithType:UIButtonTypeDetailDisclosure];
        [rightButton addTarget:self action:@selector(myButton:) forControlEvents:UIControlEventTouchUpInside];
        [rightButton setTitle:annotation.title forState:UIControlStateNormal];
        annotationView.rightCalloutAccessoryView = rightButton;
        annotationView.canShowCallout = YES;
        annotationView.draggable = YES;
        annotationView.highlighted = YES;
        return annotationView;
    }

     else if ([thisModelName isEqualToString:@"test4"])
    {
        annotationView.image = [UIImage imageNamed:@"test4"];
        UIButton* rightButton = [UIButton buttonWithType:UIButtonTypeDetailDisclosure];
        [rightButton addTarget:self action:@selector(myButton:) forControlEvents:UIControlEventTouchUpInside];
        [rightButton setTitle:annotation.title forState:UIControlStateNormal];
        annotationView.rightCalloutAccessoryView = rightButton;
        annotationView.canShowCallout = YES;
        annotationView.draggable = YES;
        annotationView.highlighted = YES;
        return annotationView;
    }
    }


     return nil;


     }

Answer 1

由于此代码，您将“随机”获取默认引脚：

MKAnnotationView *annotationView = [mapView dequeueReusableAnnotationViewWithIdentifier:AnnotationIdentifier];

if (annotationView)
    return nil;

此代码说的是dequeueReusableAnnotationViewWithIdentifier:返回视图（即如果annotationView 不 nil），则返回nil委托方法。

当您从nil委托方法返回viewForAnnotation时，地图视图会执行以下操作：

如果注释类型为MKUserLocation，则会显示默认的蓝点。
如果注释不是MKUserLocation，则会显示默认的红色针脚。

你可能意味着什么：

MKAnnotationView *annotationView = [mapView dequeueReusableAnnotationViewWithIdentifier:AnnotationIdentifier];

if (annotationView)
    return annotationView;

然而，这会产生新问题，因为如果dequeue返回一个视图（以前用于不同<的视图） / em>注释），出列视图的image可能与当前annotation应使用的图像不匹配。

因此，当您缩放并平移地图时，注释图像将“随机”切换。

viewForAnnotation中的正确方法是：

使用dequeueReusableAnnotationViewWithIdentifier:获取对视图的引用，如果返回nil，则创建一个新视图。仅在创建新视图时设置所有注释通用的视图属性。

使用步骤1中获取的视图参考，设置特定于当前annotation的视图属性。如果正在使用出列视图，请同时更新其annotation属性。

示例：

- (MKAnnotationView *)mapView:(MKMapView *)mapview viewForAnnotation:(id <MKAnnotation>)annotation { if (! [annotation isKindOfClass:[testmap class]]) { //If annotation is NOT a "testmap" (eg. MKUserLocation), //return nil so map view displays default view for it... return nil; } static NSString* AnnotationIdentifier = @"AnnotationIdentifier"; MKAnnotationView *annotationView = [mapView dequeueReusableAnnotationViewWithIdentifier:AnnotationIdentifier]; if (! annotationView) { annotationView = [[MKAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:AnnotationIdentifier]; //set view properties common to all annotations... annotationView.canShowCallout = YES; UIButton* rightButton = [UIButton buttonWithType:UIButtonTypeDetailDisclosure]; //Do not use addTarget with a custom method for callout accessories. //Instead, use the calloutAccessoryControlTapped delegate method shown below. annotationView.rightCalloutAccessoryView = rightButton; annotationView.draggable = YES; } else { //reusing a view, update its annotation to current... annotationView.annotation = annotation; } //AFTER we have a view reference, set annotation-specific properties... NSString* thisModelName = ((testmap*)annotation).name; if ([thisModelName isEqualToString:@"test1"]) { annotationView.image = [UIImage imageNamed:@"test1"]; } else if ([thisModelName isEqualToString:@"test2"]) { annotationView.image = [UIImage imageNamed:@"test2"]; } else if ([thisModelName isEqualToString:@"test3"]) { annotationView.image = [UIImage imageNamed:@"test3"]; } else if ([thisModelName isEqualToString:@"test4"]) { annotationView.image = [UIImage imageNamed:@"test4"]; } /* If image name will always be same as `name` property then can use single line instead of if/else statements: annotationView.image = [UIImage imageNamed:thisModelName]; */ return annotationView; } -(void)mapView:(MKMapView *)mapView annotationView:(MKAnnotationView *)view calloutAccessoryControlTapped:(UIControl *)control { if ([view.annotation isKindOfClass:[testmap class]]) { testmap *tm = (testmap *)view.annotation; NSLog(@"button for '%@' tapped", tm.name); } }

将注释从显示图像交换到默认引脚

1 个答案: