|
我正在执行 willChangeValueForKey 和 didChangeValueForKey 调用，但即使使用它们，mapView 委托(delegate)也永远不会通过 mapView: viewForAnnotation: 来更新事情。如何强制更新 MKAnnotation？
annotationView.image 不会在图像更改时更新，annotationView.image 也不会更新。据我的 NSLog 行所知，当 MKAnnotation 更新时，mapView: viewForAnnotation: 不会再次被调用。
.h
#import <UIKit/UIKit.h>
#import <Foundation/Foundation.h>
#import <MapKit/MapKit.h>
@interface MapAnnotation : NSObject <MKAnnotation>
@property (nonatomic, assign) CLLocationCoordinate2D coordinate;
@property (nonatomic, retain) NSString *currentTitle;
@property (nonatomic, retain) NSString *currentSubTitle;
@property (nonatomic, retain) NSString *category;
@property (nonatomic, retain) NSString *pin;
- (NSString*) title;
- (NSString*) subtitle;
- (id) initWithCoordinate CLLocationCoordinate2D) c;
- (CLLocationCoordinate2D) getCoordinate;
- (void) addPlaceMapAnnotation*) place;
- (int) placesCount;
- (void) cleanPlaces;
- (UIImage *) getPin;
@end
.m
#import "MapAnnotation.h"
@interface MapAnnotation()
@property (strong) NSMutableArray *places;
@end
@implementation MapAnnotation
@synthesize coordinate = _coordinate;
@synthesize currentTitle = _currentTitle;
@synthesize currentSubTitle = _currentSubTitle;
@synthesize places = _places;
@synthesize category = _category;
@synthesize pin = _pin;
- (NSString*) subtitle {
if ([self placesCount] == 1) {
return self.currentSubTitle;
}
else{
return @"";
}
}
- (NSString*) title {
if ([self placesCount] == 1) {
return self.currentTitle;
}
else{
return [NSString stringWithFormat "%d places", [self placesCount]];
}
}
- (void)addPlaceMapAnnotation *)place {
[self willChangeValueForKey"title"];
[self willChangeValueForKey"subtitle"];
[self.places addObject:place];
[self didChangeValueForKey"title"];
[self didChangeValueForKey"subtitle"];
}
- (CLLocationCoordinate2D)getCoordinate {
return self.coordinate;
}
- (void)cleanPlaces {
[self willChangeValueForKey"title"];
[self willChangeValueForKey"subtitle"];
[self.places removeAllObjects];
[self.places addObject:self];
[self didChangeValueForKey"title"];
[self didChangeValueForKey"subtitle"];
}
- (id)initWithCoordinateCLLocationCoordinate2D) c {
self.coordinate=c;
self.places=[[NSMutableArray alloc] initWithCapacity:0];
return self;
}
- (int)placesCount {
return [self.places count];
}
- (UIImage *)getPin {
// begin a graphics context of sufficient size
CGSize size = CGSizeMake(26, 26);
UIGraphicsBeginImageContextWithOptions(size, NO, 0.0);
// get the context for CoreGraphics
CGContextRef ctx = UIGraphicsGetCurrentContext();
CGRect imageRect = CGRectMake(0, 0, size.width, size.height);
// Draw Dot
CGRect circleRect = CGRectInset(imageRect, 4, 4);
[[UIColor blackColor] setStroke];
[[UIColor yellowColor] setFill];
CGContextFillEllipseInRect(ctx, circleRect);
CGContextStrokeEllipseInRect(ctx, circleRect);
// Dot Content
[[UIColor blackColor] setStroke];
[[UIColor blackColor] setFill];
CGAffineTransform transform = CGAffineTransformMake(1.0, 0.0, 0.0, -1.0, 0.0, 0.0);
CGContextSetTextMatrix(ctx, transform);
CGContextSetLineWidth(ctx, 2.0);
CGContextSetCharacterSpacing(ctx, 1.7);
CGContextSetTextDrawingMode(ctx, kCGTextFill);
UIFont *font = [UIFont fontWithName"Arial" size:11.0];
if ([self placesCount] != 1) {
NSString *label = [NSString stringWithFormat:@"%d", [self placesCount]];
CGSize stringSize = [label sizeWithAttributes:@{NSFontAttributeName:font}];
[label drawAtPoint:CGPointMake(size.width / 2 - stringSize.width / 2, size.height / 2 - stringSize.height / 2)
withAttributes:@{NSFontAttributeName:font}];
} else {
NSString *label = [NSString stringWithFormat:@"%@", self.pin];
CGSize stringSize = [label sizeWithAttributes:@{NSFontAttributeName:font}];
[label drawAtPoint:CGPointMake(size.width / 2 - stringSize.width / 2, size.height / 2 - stringSize.height / 2)
withAttributes:@{NSFontAttributeName:font}];
}
// make image out of bitmap context
UIImage *retImage = UIGraphicsGetImageFromCurrentImageContext();
// free the context
UIGraphicsEndImageContext();
return retImage;
}
@end
mapView:viewForAnnotation:
- (MKAnnotationView *)mapViewMKMapView *)mapView viewForAnnotationid <MKAnnotation>)annotation {
MKAnnotationView *annotationView = [mapView dequeueReusableAnnotationViewWithIdentifier:@"MyAnnoation"];
if(!annotationView) {
annotationView = [[MKAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:@"MyAnnoation"];
annotationView.rightCalloutAccessoryView = [UIButton buttonWithType:UIButtonTypeDetailDisclosure];
}
annotationView.enabled = YES;
if ([(MapAnnotation*)annotation placesCount] == 1) {
annotationView.canShowCallout = YES;
}
annotationView.image = [(MapAnnotation*)annotation getPin];
NSLog(@"%@", [annotation title]);
return annotationView;
}
Best Answer-推荐答案
正如评论中提到的，除了 title 和 subtitle 之外，注释属性的更改不会自动导致 View 更新。
更改 title 和 subtitle 将在显示时自动更新标注，只要更改导致 KVO 通知(例如，如果使用带有 ann.title = xxx 或通过手动发出 KVO 通知，因为您有自定义 getter)。
要自动更新图像，您可能需要使用自定义注释 View 来观察底层注释属性的变化并自行刷新(在 init 中调用 addObserver ，在observeValueForKeyPath更新图片，在dealloc调用removeObserver)。您也可以使用非 KVO 方法，例如自定义通知或委托(delegate)(但仍使用自定义注释 View )来实现。
使用现有代码，在不创建自定义注释 View 和使用KVO等的情况下，快速手动更新注释 View 的方法是在注释更新后立即获取注释的当前 View 并更新图像 属性。只要 viewForAnnotation 中的代码与设置 image 的逻辑相同，这应该可以工作。
我假设在应用程序的某个地方(有时在注释已经添加)，它通过调用addPlace来更新注释中的位置。之后，您可以尝试以下操作:
[someExistingAnnotation addPlace:anotherPlace];
//obtain the current view of someExistingAnnotation...
MKAnnotationView *av = [mapView viewForAnnotation:someExistingAnnotation];
//update its image property to force refresh...
av.image = [someExistingAnnotation getPin];
//also set canShowCallout (it might have been NO)
不相关但当前的 viewForAnnotation 不能正确处理可能的 View 重用和/或除您的自定义注释之外的注释类型(例如会导致当前代码崩溃的用户位置蓝点)。我建议将其更改为:
- (MKAnnotationView *)mapViewMKMapView *)mapView viewForAnnotationid <MKAnnotation>)annotation {
if (! [annotation isKindOfClass:[MapAnnotation class]])
{
//annotation is NOT a "MapAnnotation", return nil for default view...
return nil;
}
MKAnnotationView *annotationView = [mapView dequeueReusableAnnotationViewWithIdentifier:@"MyAnnoation"];
if(!annotationView) {
annotationView = [[MKAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:@"MyAnnoation"];
annotationView.rightCalloutAccessoryView = [UIButton buttonWithType:UIButtonTypeDetailDisclosure];
}
//update view's annotation to current in case it's being re-used
annotationView.annotation = annotation;
annotationView.enabled = YES;
if ([(MapAnnotation*)annotation placesCount] == 1) {
annotationView.canShowCallout = YES;
}
else {
annotationView.canShowCallout = NO;
}
annotationView.image = [(MapAnnotation*)annotation getPin];
NSLog(@"%@", [annotation title]);
return annotationView;
}
关于ios - 自定义注释在更新时不会在 map View 上更新，我们在Stack Overflow上找到一个类似的问题：
https://stackoverflow.com/questions/20026321/
| 
客服电话
APP下载
官方微信
