/** 更新标注展示. */
- (void)updateClusters {
    _clusterZoom = (NSInteger)_mapView.zoomLevel;
    @synchronized(_clusterManager.clusterCaches) {
            NSMutableArray *clusters = [_clusterManager.clusterCaches objectAtIndex:(_clusterZoom - 3)];
        if (clusters.count > 0) {
    
            // 移除一组标注
            [_mapView removeAnnotations:_mapView.annotations];
            //将一组标注添加到当前地图View中
            [_mapView addAnnotations:clusters];
        } else {
            __weak typeof(self) weakSelf = self;
            dispatch_async(dispatch_get_global_queue(0, 0), ^{
                // 获取聚合后的标注
                __block NSArray *array = [weakSelf.clusterManager getClusters:weakSelf.clusterZoom];
                dispatch_async(dispatch_get_main_queue(), ^{
                    for (BMKCluster *item in array) {
                        ClusterAnnotation *annotation = [[ClusterAnnotation alloc] init];
                        // 设置标注的经纬度坐标
                        annotation.coordinate = item.coordinate;
                        annotation.size = item.size;
                        // 设置标注的标题
                        annotation.title = [NSString stringWithFormat:@"我是%lu个", (unsigned long)item.size];
                        [clusters addObject:annotation];
                    }
                    // 移除一组标注
                    [weakSelf.mapView removeAnnotations:weakSelf.mapView.annotations];
                    // 将一组标注添加到当前地图View中
                    [weakSelf.mapView addAnnotations:clusters];
                });
            });
        }
    }
}

#pragma mark - BMKMapViewDelegate
/** 根据anntation生成对应的View. */
- (BMKAnnotationView *)mapView:(BMKMapView *)mapView viewForAnnotation:(id <BMKAnnotation>)annotation {
        ClusterAnnotation *cluster = (ClusterAnnotation*)annotation;
        BMKPinAnnotationView *annotationView = [[BMKPinAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:annotationViewIdentifier];
        UILabel *annotationLabel = [[UILabel alloc] init];
        annotationLabel.textColor = [UIColor whiteColor];
        annotationLabel.font = [UIFont systemFontOfSize:11];
        annotationLabel.textAlignment = NSTextAlignmentCenter;
        annotationLabel.hidden = NO;
        annotationLabel.text = [NSString stringWithFormat:@"%ld", (long)cluster.size];
        annotationLabel.backgroundColor = [UIColor greenColor];
        annotationView.alpha = 0.8;
        [annotationView addSubview:annotationLabel];
        // 此处为了方便展示使用了简易的大头针标注，开发者可以根据自身需求来自定义标注，圆角设置建议使用圆形图片
        if (cluster.size == 1) {
            annotationLabel.hidden = YES;
            annotationView.pinColor = BMKPinAnnotationColorRed;
        }
        if (cluster.size >= 500) {
            annotationLabel.frame = CGRectMake(0, 0, 100, 100);
            annotationLabel.layer.cornerRadius = 50;
            annotationLabel.layer.masksToBounds = YES;
            annotationLabel.backgroundColor = [UIColor redColor];
            [annotationView setBounds:CGRectMake(0, 0, 100, 100)];
        } else if (cluster.size >= 200 && cluster.size < 500) {
            annotationLabel.frame = CGRectMake(0, 0, 80, 80);
            annotationLabel.layer.cornerRadius = 40;
            annotationLabel.layer.masksToBounds = YES;
            annotationLabel.backgroundColor = [UIColor purpleColor];
            [annotationView setBounds:CGRectMake(0, 0, 80, 80)];
        } else if (cluster.size > 50) {
            annotationLabel.frame = CGRectMake(0, 0, 60, 60);
            annotationLabel.layer.cornerRadius = 30;
            annotationLabel.layer.masksToBounds = YES;
            annotationLabel.backgroundColor = [UIColor orangeColor];
            [annotationView setBounds:CGRectMake(0, 0, 60, 60)];
        } else if (cluster.size > 20) {
            annotationLabel.frame = CGRectMake(0, 0, 40, 40);
            annotationLabel.layer.cornerRadius = 20;
            annotationLabel.layer.masksToBounds = YES;
            annotationLabel.backgroundColor = [UIColor blueColor];
            [annotationView setBounds:CGRectMake(0, 0, 40, 40)];
        } else {
            annotationLabel.frame = CGRectMake(0, 0, 20, 20);
            annotationLabel.layer.cornerRadius = 10;
            annotationLabel.layer.masksToBounds = YES;
            annotationLabel.backgroundColor = [UIColor greenColor];
            [annotationView setBounds:CGRectMake(0, 0, 20, 20)];
        }
        annotationView.draggable = YES;
        annotationView.annotation = annotation;
        return annotationView;
}

/** 当点击annotationView弹出的泡泡时，回调此方法. */
- (void)mapView:(BMKMapView *)mapView annotationViewForBubble:(BMKAnnotationView *)view {
    if ([view isKindOfClass:[BMKPinAnnotationView class]]) {
        ClusterAnnotation *clusterAnnotation = (ClusterAnnotation*)view.annotation;
        if (clusterAnnotation.size > 1) {
            /**
                设定地图中心点坐标
                @param coordinate 要设定的地图中心点坐标，用经纬度表示
                @param animated 是否采用动画效果
                */
            [mapView setCenterCoordinate:view.annotation.coordinate];
            /**
                放大一级比例尺
                
                @return 是否成功
                */
            [mapView zoomIn];
        }
    }
}

    /** 地图加载完成时会调用此方法. */
- (void)mapViewDidFinishLoading:(BMKMapView *)mapView {
    [self updateClusters];
}

    /** 地图渲染每一帧画面过程中，以及每次需要重新绘制地图时(例如添加覆盖物)都会调用此方法*/
- (void)mapView:(BMKMapView *)mapView onDrawMapFrame:(BMKMapStatus *)status {
    if (_clusterZoom != 0 && _clusterZoom != (NSInteger)mapView.zoomLevel) {
        [self updateClusters];
    }
}