MKPolyline解析csv？

Question

基本上，我想用这段代码画一条折线。如您所见，我已经准备好了覆盖方法，我只需要知道如何在(void)viewDidLoad中调用viewDidLoad

更新OK，所以我设法画了多条线。然而，这些线是没有意义的，它们连接一些没有顺序的引脚，然后4个引脚释放出一条指向地图西北的线，我需要知道如何使它以有序的方式将一个引脚连接到另一个引脚上。

- (void)viewDidLoad {
[super viewDidLoad];



NSString *csvFilePath = [[NSBundle mainBundle] pathForResource:@"Data" ofType:@"csv"];
NSString *dataStr = [NSString stringWithContentsOfFile:csvFilePath encoding:NSUTF8StringEncoding error:nil];

NSArray* allLinedStrings = [dataStr componentsSeparatedByCharactersInSet:[NSCharacterSet newlineCharacterSet]];

MKMapPoint northEastPoint;
MKMapPoint southWestPoint;

MKMapPoint* pointArr = malloc(sizeof(CLLocationCoordinate2D) * allLinedStrings.count);

for(int idx = 0; idx < allLinedStrings.count; idx++)
{

    NSString* currentPointString = [allLinedStrings objectAtIndex:idx];
    NSArray* infos = [currentPointString componentsSeparatedByCharactersInSet:[NSCharacterSet characterSetWithCharactersInString:@","]];
    if ([infos count] > 1)
    {
        NSString * latitude = [infos objectAtIndex:1];
        NSString * longitude = [infos objectAtIndex:2];
        NSString * Description =[infos objectAtIndex:3];
        NSString * address = [infos objectAtIndex:4];

        CLLocationCoordinate2D coordinate;
        coordinate.latitude = latitude.doubleValue;
        coordinate.longitude = longitude.doubleValue;
        Location *annotation = [[Location alloc] initWithName:Description address:address coordinate:coordinate] ;
        [mapview addAnnotation:annotation];

        MKMapPoint point = MKMapPointForCoordinate(coordinate);

        //
        // adjust the bounding box
        //

        // if it is the first point, just use them, since we have nothing to compare to yet.
        if (idx == 0) {
            northEastPoint = point;
            southWestPoint = point;
        }
        else
        {
            if (point.x > northEastPoint.x)
                northEastPoint.x = point.x;
            if(point.y > northEastPoint.y)
                northEastPoint.y = point.y;
            if (point.x < southWestPoint.x)
                southWestPoint.x = point.x;
            if (point.y < southWestPoint.y)
                southWestPoint.y = point.y;
        }

        pointArr[idx] = point;

    }

    self.routeLine = [MKPolyline polylineWithPoints:pointArr count:allLinedStrings.count];

    _routeRect = MKMapRectMake(southWestPoint.x, southWestPoint.y, northEastPoint.x - southWestPoint.x, northEastPoint.y - southWestPoint.y);
    [self.mapview addOverlay:self.routeLine];

}


    }
  }
}         
 - (MKOverlayRenderer *)mapView:(MKMapView *)mapView
        rendererForOverlay:(id < MKOverlay >)overlay
 {
 MKPolylineRenderer *renderer =
 [[MKPolylineRenderer alloc] initWithPolyline:overlay];
 renderer.strokeColor = [[UIColor orangeColor] colorWithAlphaComponent:1];
 renderer.lineWidth = 6.0;
renderer.lineDashPattern = @[@2, @10];
renderer.alpha = 0.5;

return renderer;

}

另外，我的csv文件如果有任何帮助

01,51.751782,-0.238992, Location 1, 1st Stop
02,51.815020,-0.200418, Location 2, 2nd Stop
03,51.755462,-0.340392, Location 3, 3rd Stop
04,51.660507,-0.389374, Location 4, 4th Stop
05,51.798323,-0.081622, Location 5, 5th Stop

Answer 1

当每个坐标被添加到C数组时(在设置数组中的所有其他坐标之前)，将添加一个覆盖。这会导致线路向西北方向延伸。在循环之后创建并添加覆盖。

下面是对当前代码的总结，并仅指出相关部分：

MKMapPoint* pointArr = malloc(sizeof(CLLocationCoordinate2D) * allLinedStrings.count);

for(int idx = 0; idx < allLinedStrings.count; idx++)
{
    //some code that gets "infos" (current coordinate's data)...

    if ([infos count] > 1)
    {
        //some code that creates and adds an annotation...

        MKMapPoint point = MKMapPointForCoordinate(coordinate);

        //some code that calculates the "bounding box" (irrelevant)...

        pointArr[idx] = point;    
    }

    self.routeLine = [MKPolyline polylineWithPoints:pointArr count:allLinedStrings.count];

    //_routeRect = ... (irrelevant)

    [self.mapview addOverlay:self.routeLine];

} //end of for-loop

注意，addOverlay调用位于for-loop中，这意味着为每个坐标添加了一个polyline覆盖。

但是，在每次迭代时，pointArr数组尚未完全填充：

• 当pointArr[0]设置为location 1时，还没有将pointArr[1]设置为pointArr[4]，并且包含零值或随机值。
• 当pointArr[1]设置为位置2时，还没有将pointArr[2]设置为pointArr[4]并包含零值或随机值等.

在每个坐标/迭代中，pointArr部分设置为这样，增加了折线，导致随机线进入西北方向。

相反，只需在for-loop之后和pointArr完全填充之后创建并添加polyline覆盖：

MKMapPoint* pointArr = malloc(sizeof(CLLocationCoordinate2D) * allLinedStrings.count);

for(int idx = 0; idx < allLinedStrings.count; idx++)
{
    //some code that gets "infos" (current coordinate's data)...

    if ([infos count] > 1)
    {
        //some code that creates and adds an annotation...

        MKMapPoint point = MKMapPointForCoordinate(coordinate);

        //some code that calculates the "bounding box" (irrelevant)...

        pointArr[idx] = point;    
    }

    //_routeRect = ... (irrelevant)

} //end of for-loop

self.routeLine = [MKPolyline polylineWithPoints:pointArr count:allLinedStrings.count];

[self.mapview addOverlay:self.routeLine];

​

还有几点：

​

1. 这个malloc在技术上是错误的： MKMapPoint* pointArr = malloc(sizeof(CLLocationCoordinate2D) * allLinedStrings.count)； 它定义了一个MKMapPoint结构数组，但是使用了CLLocationCoordinate2D结构的大小。由于您打算添加MKMapPoint结构，所以应该使用该结构的大小： MKMapPoint* pointArr = malloc(sizeof(MKMapPoint) * allLinedStrings.count)； 它仍然“工作”错误的原因是因为MKMapPoint和CLLocationCoordinate2D恰好是相同的大小。
2. 您正在使用malloc分配C数组，但不释放内存。在不再需要pointArr之后，应该调用free： self.routeLine = MKPolyline polylineWithPoints:pointArr count:allLinedStrings.count；self.mapview addOverlay:self.routeLine；free(pointArr)；
3. 只是FYI:因为您有CLLocationCoordinate2D坐标值，所以您可以使用polylineWithCoordinates创建polyline，并省去将它们转换为MKMapPoint的麻烦。
4. 包围盒的计算似乎比必要的要复杂。更简单的方法是将MKMapRect初始化为MKMapRectNull，然后使用MKMapRectUnion将每个注释的MKMapPoint添加到它。有关示例，请参见this answer。更简单的是，在添加了所有注释之后，只需调用[self.mapview showAnnotations:self.mapview.annotations animated:YES];。