MKAnnotationView自定义按钮图像

Question

我正在尝试使用自定义图像,MKAnnotationView当我使用以下代码时,我的注释上没有图像.我已经检查了调试,以确保图像正确加载到UIImage.

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


    MKAnnotationView *annotationView = [mapView dequeueReusableAnnotationViewWithIdentifier:@"String"];
    if(!annotationView) {

        annotationView = [[MKAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:@"String"];
        UIButton *directionButton = [UIButton buttonWithType:UIButtonTypeCustom];
        UIImage *directionIcon = [UIImage imageNamed:@"IconDirections"];

        [directionButton setImage:directionIcon forState:UIControlStateNormal];

        annotationView.rightCalloutAccessoryView = directionButton;
    }

    annotationView.enabled = YES;
    annotationView.canShowCallout = YES;

    return annotationView;
}

Answer 1

有两个主要问题:

1. 在frame自定义标注按钮没有被设置使得它基本上是不可见的.
2. 一个MKAnnotationView被创建,但其image属性(注释本身的形象-没有标注按钮的)未设置.这使得整个注释不可见.

对于问题1,将按钮的框架设置为适当的值.例如:

UIImage *directionIcon = [UIImage imageNamed:@"IconDirections"];
directionButton.frame = 
    CGRectMake(0, 0, directionIcon.size.width, directionIcon.size.height);

对于问题2,设置注释视图image(或创建MKPinAnnotationView代替):

annotationView.image = [UIImage imageNamed:@"SomeIcon"];

此外,您应该通过更新annotation属性来正确处理视图重用.
完整的例子:

- (MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:(id <MKAnnotation>)annotation 
{    
    MKAnnotationView *annotationView = [mapView dequeueReusableAnnotationViewWithIdentifier:@"String"];
    if(!annotationView) {

        annotationView = [[MKAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:@"String"];

        annotationView.image = [UIImage imageNamed:@"SomeIcon"];

        UIButton *directionButton = [UIButton buttonWithType:UIButtonTypeCustom];
        UIImage *directionIcon = [UIImage imageNamed:@"IconDirections"];
        directionButton.frame = 
            CGRectMake(0, 0, directionIcon.size.width, directionIcon.size.height);

        [directionButton setImage:directionIcon forState:UIControlStateNormal];

        annotationView.rightCalloutAccessoryView = directionButton;
        annotationView.enabled = YES;
        annotationView.canShowCallout = YES;
    }
    else {
        //update annotation to current if re-using a view
        annotationView.annotation = annotation;
    }    

    return annotationView;
}