我正在尝试使用无限量的注释填充 MKMapView，这些注释在用户滚动地图时可以查看。显然，用户必须放大到足够远才能显示视图，因为如果不是这样的话，应用程序处理的太多了，一次只能显示大约 20 个。
我有一个包含大约 100 个对象的数组，我需要在整个地图的随机位置随机重复这些对象。这些是在运行时使用 MKMapView 的 visibleMapRect 属性创建的，仅创建必要的。我还实现了一个缓存字典，以防止重新创建以前创建的对象。这是我简化的当前代码：
@property (nonatomic, strong) NSArray *mapObjects; //Contains 100 objects to be repeated
@property (nonatomic, strong) NSMutableDictionary *cache; //Cache already created mapObjects
//Constants used
int const MapDensity = 5000.0; //Density of annotations
int const MapZoomMax = 30000.0; //Max zoom level to show annotations
- (void)loadLocations {
MKMapRect rect = [mapView visibleMapRect];
if (rect.size.width > MapZoomMax) {
[self performSelectorOnMainThread:@selector(removeAllAnnotations) withObject:nil waitUntilDone:NO];
return;
}
rect.origin.x = MapDensity*floor(rect.origin.x/MapDensity);
rect.origin.y = MapDensity*floor(rect.origin.y/MapDensity);
MKMapPoint pointLocation = rect.origin;
NSMutableArray *locationsArray = [NSMutableArray array];
while (pointLocation.y < rect.origin.y+rect.size.height) {
while (pointLocation.x < rect.origin.x+rect.size.width) {
int cacheKey = pointLocation.x*pointLocation.y;
if (![self.cache objectForKey:[NSNumber numberWithInt:cacheKey]]) {
//Adjust for randomness
MKMapPoint pointLocationAdjusted = pointLocation;
pointLocationAdjusted.x += arc4random()%MapDensity;
pointLocationAdjusted.y += arc4random()%MapDensity;
//Create annotation
GLAnnotation *annotation = [[GLAnnotation alloc] init];
[annotation setCoordinate:MKCoordinateForMapPoint(pointLocationAdjusted)];
[annotation setMapObject:[self.mapObjects objectAtIndex:(arc4random()%[mapObjects count])]];
[locationsArray addObject:annotation];
[self.cache setObject:annotation forKey:[NSNumber numberWithInt:cacheKey]];
} else {
[locationsArray addObject:[self.cache objectForKey:[NSNumber numberWithInt:cacheKey]]];
}
pointLocation.x += MapDensity; //Go to next X
}
pointLocation.x = rect.origin.x; //Restart X
pointLocation.y += MapDensity; //Go to next Y
}
[self performSelectorOnMainThread:@selector(addAnnotations:) withObject:locationsArray waitUntilDone:NO];
}
- (void)addAnnotations:(NSArray *)annotations {
NSMutableArray *newAnnotations = [NSMutableArray array];
for (id annotation in annotations) {
if (![mapView.annotations containsObject:annotation]) {
[mapView addObject:annotation];
}
}
[mapView addAnnotations:newAnnotations];
}
- (void)mapView:(MKMapView *)mapView regionDidChangeAnimated:(BOOL)animated {
[self performSelectorInBackground:@selector(loadLocations) withObject:nil];
}
- (MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:(id <MKAnnotation>)annotation {
if([annotation isKindOfClass:[GLAnnotation class]]){
static NSString *annotationIdentifier = @"AnnotationIdentifier";
MKAnnotationView *annotationView = [mapView dequeueReusableAnnotationViewWithIdentifier:annotationIdentifier];
if(!annotationView){
annotationView = [[MKAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:annotationIdentifier];
annotationView.canShowCallout = YES;
}
annotationView.image = [(GLAnnotation *)annotation picture];
return annotationView;
}
return nil;
}
该代码似乎大部分时间都可以工作，但有时会导致地图滚动滞后（我试图解决在后台线程中运行它的问题）并且通常会使应用程序崩溃，这似乎是由内存问题引起的（我试图修复使用缓存）。不输出任何错误消息，除了：EXC_BAD_ACCESS。如果有人能告诉我如何正确管理这么多的注释，我将不胜感激。