处理大量 MKMapView 注解

发布于 2024-10-14 07:42:42 字数 876 浏览 4 评论 0原文

我有一个带有大量注释（3000+）的地图视图，当用户缩放到合理的级别时，一切都很好而且很快。

尽管当用户缩小并看到大量注释时，由于一次显示的注释数量巨大，速度会显着减慢。处理这个问题的最佳方法是什么？

我当前使用的解决方案：

- (void)mapView:(MKMapView *)_mapView regionDidChangeAnimated:(BOOL)animated {

    NSArray *annotations = [_mapView annotations];  
    MapAnnotation *annotation = nil; 

    for (int i=0; i<[annotations count]; i++)
    {
        annotation = (MapAnnotation*)[annotations objectAtIndex:i];
        if (_mapView.region.span.latitudeDelta > .010)
        {
            [[_mapView viewForAnnotation:annotation] setHidden:YES];
            warningLabel.hidden = NO;
        }
        else {
            [[_mapView viewForAnnotation:annotation] setHidden:NO];
            warningLabel.hidden = YES;
        }
    }
}

效果很好，尽管由于循环的巨大尺寸，这会导致放大、缩小和滚动时速度减慢很多。我似乎想不出更好的方法来处理这个问题，有没有办法只循环当前显示的注释或类似的东西来减少循环的大小？

原文

I have a map view with a large quantity of annotations (3000+), when the user is zoomed to a reasonable level all is well and fast.

Although when the user zooms out and a large quanitiy of annotations come into view there is a lot of slow down due to the sheer amount of annotations being shown at once. What is the best way to handle this?

The current solution i am using:

- (void)mapView:(MKMapView *)_mapView regionDidChangeAnimated:(BOOL)animated {

    NSArray *annotations = [_mapView annotations];  
    MapAnnotation *annotation = nil; 

    for (int i=0; i<[annotations count]; i++)
    {
        annotation = (MapAnnotation*)[annotations objectAtIndex:i];
        if (_mapView.region.span.latitudeDelta > .010)
        {
            [[_mapView viewForAnnotation:annotation] setHidden:YES];
            warningLabel.hidden = NO;
        }
        else {
            [[_mapView viewForAnnotation:annotation] setHidden:NO];
            warningLabel.hidden = YES;
        }
    }
}

Works great although due to the sheer size of the loop this causes a lot of slow down when zooming in and out and scrolling around. I can't seem to think of a better way to handle this, is there a way to only loop through the annotations currently being displayed or something along those lines to reduce the size of the loop?

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揪着可爱 2024-10-21 07:42:42

据我了解您的代码，如果地图视图缩小超过某个指定值，您将隐藏所有注释的视图。

在我看来，像下面这样的东西会更好：

- (void)mapView: (MKMapView*)_mapView regionDidChangeAnimated: (BOOL)animated
{
    if (_mapView.region.span.latitudeDelta > .010 && self.mapViewsHidden == NO) {
        for (MapAnnotation* annotation in _mapView.annotations) {
            [[_mapView viewForAnnotation: annotation] setHidden: YES];
        }
        [self.warningLabel setHidden: NO];
        [self setMapViewsHidden: YES];
    }
    else if (_mapView.region.span.latitudeDelta <= .010 && self.mapViewsHidden == YES) {
        for (MapAnnotation* annotation in _mapView.annotations) {
            [[_mapView viewForAnnotation: annotation] setHidden: NO];
        }
        [self.warningLabel setHidden: YES];
        [self setMapViewsHidden: NO];
    }
}

有了上面的内容，在大多数情况下，这段代码所做的唯一事情就是进行一些 if 检查。

另一种解决方案是在注释不应显示在地图上时删除注释。就我个人而言，我认为这会更好，这样代码就不必为尚未在地图上显示的注释创建视图。

As I understand your code, you are hiding all the annotations' views if the mapView is zoomed out more than a certain specified value.

It seems to me that something more like the following would be better:

- (void)mapView: (MKMapView*)_mapView regionDidChangeAnimated: (BOOL)animated
{
    if (_mapView.region.span.latitudeDelta > .010 && self.mapViewsHidden == NO) {
        for (MapAnnotation* annotation in _mapView.annotations) {
            [[_mapView viewForAnnotation: annotation] setHidden: YES];
        }
        [self.warningLabel setHidden: NO];
        [self setMapViewsHidden: YES];
    }
    else if (_mapView.region.span.latitudeDelta <= .010 && self.mapViewsHidden == YES) {
        for (MapAnnotation* annotation in _mapView.annotations) {
            [[_mapView viewForAnnotation: annotation] setHidden: NO];
        }
        [self.warningLabel setHidden: YES];
        [self setMapViewsHidden: NO];
    }
}

With the above, in most cases the only thing this code does is a couple of if checks.

Another solution would be to remove the annotations when they shouldn't show on the map. Personally, I think this would be better, that way the code doesn't have to create views for annotations that haven't been shown on the map yet.

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趁微风不噪 2024-10-21 07:42:42

我会建议几件事。一、查看annotationsInMapRect:方法。根据文档，它说：

此方法提供了一种检索地图特定部分中的注释对象的快速方法。此方法比您自己对注释属性中的对象进行线性搜索要快得多。

二、查看dequeueReusableAnnotationViewWithIdentifier：。再次根据文档，它说：

出于性能原因，您通常应该在地图视图中重用 MKAnnotationView 对象。当注释视图移出屏幕时，地图视图将它们移至内部管理的重用队列。当新注释在屏幕上移动时，系统会提示您的代码提供相应的注释视图，您应该始终尝试在创建新视图之前使现有视图出列。出队可以在滚动等性能关键操作期间节省时间和内存。

最后，有几点想法。与其每次调用 - (void)mapView:(MKMapView *)_mapView RegionDidChangeAnimated:(BOOL)animated 方法时都进行这些更改，不如根据其他规则（例如在计时器被触发[确保每次调用时重置计时器]）？另一件需要考虑的事情是：如何将彼此非常接近的注释分组在一起？假设您缩小到罗德岛看起来非常小，可能只有十几个像素宽，并且您在罗德岛有 100 个点 - 您应该只显示一个图钉。

希望这有帮助！