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在MKMapView中添加渐变色路径

2018-06-08  本文已影响58人  口子窖

刚来苏宁接触到的业务并不多，既然要写博客那就暂时上一篇之前所遇到的关于在地图控件中如何添加渐变色路径实现方案吧。

整体实现原理是依据用户跑步配速将坐标点等分为若干色块，将色块相连就形成了渐变色轨迹

如何在iPhone上绘制mapView就不说了，在mapView上绘制轨迹要添加MKPolyline，调用[self.mapView addOverlay:self.polyLine]；但这个MKPolyline的构造方法中只接受和坐标相关的值，而轨迹渐变自然要通过速度控制，但传不进去，所以只能重写一个实现<MKOverlay>协议的类。下面就是我找到的，拿去可以直接用：

GradientPolylineOverlay.h实现

import <Foundation/Foundation.h>

import <MapKit/MapKit.h>

@interface GradientPolylineOverlay : NSObject <MKOverlay>{
MKMapPoint *points;
NSUInteger pointCount;
NSUInteger pointSpace;

MKMapRect boundingMapRect;
pthread_rwlock_t rwLock;

}

//Initialize the overlay with the starting coordinate.
//The overlay's boundingMapRect will be set to a sufficiently large square
//centered on the starting coordinate.
-(id) initWithCenterCoordinate:(CLLocationCoordinate2D)coord;

-(id) initWithPoints:(CLLocationCoordinate2D)_points velocity:(float)_velocity count:(NSUInteger)_count;

//Add a location observation. A MKMapRect containing the newly added point
//and the previously added point is returned so that the view can be updated
//int that rectangle. If the added coordinate has not moved far enough from
//the previously added coordinate it will not be added to the list and
//MKMapRectNULL will be returned.
//
-(MKMapRect)addCoordinate:(CLLocationCoordinate2D)coord;

-(void) lockForReading;

//The following properties must only be accessed when holding the read lock
// via lockForReading. Once you're done accessing the points, release the
// read lock with unlockForReading.
//
@property (assign) MKMapPoint *points;
@property (readonly) NSUInteger pointCount;
@property (assign) float *velocity;

-(void) unlockForReading;

@end
GradientPolylineOverlay.m

import "GradientPolylineOverlay.h"

import <pthread.h>

define INITIAL_POINT_SPACE 1000

define MINIMUM_DELTA_METERS 10.0

@implementation GradientPolylineOverlay{
}

@synthesize points, pointCount, velocity;

-(id) initWithCenterCoordinate:(CLLocationCoordinate2D)coord{
self = [super init];
if (self){
//initialize point storage and place this first coordinate in it
pointSpace = INITIAL_POINT_SPACE;
points = malloc(sizeof(MKMapPoint)*pointSpace);
points[0] = MKMapPointForCoordinate(coord);
pointCount = 1;

    //bite off up to 1/4 of the world to draw into
    MKMapPoint origin = points[0];
    origin.x -= MKMapSizeWorld.width/8.0;
    origin.y -= MKMapSizeWorld.height/8.0;
    MKMapSize size = MKMapSizeWorld;
    size.width /=4.0;
    size.height /=4.0;
    boundingMapRect = (MKMapRect) {origin, size};
    MKMapRect worldRect = MKMapRectMake(0, 0, MKMapSizeWorld.width, MKMapSizeWorld.height);
    boundingMapRect = MKMapRectIntersection(boundingMapRect, worldRect);

    // initialize read-write lock for drawing and updates
    pthread_rwlock_init(&rwLock,NULL);
}
return self;

}

-(id) initWithPoints:(CLLocationCoordinate2D*)_points velocity:(float )_velocity count:(NSUInteger)_count{
self = [super init];
if (self){
pointCount = _count;
self.points = malloc(sizeof(MKMapPoint)pointCount);
for (int i=0; i<_count; i++){
self.points[i] = MKMapPointForCoordinate(_points[i]);
}

    self.velocity = malloc(sizeof(float)*pointCount);
    for (int i=0; i<_count;i++){
        self.velocity[i] = _velocity[i];
    }

    //bite off up to 1/4 of the world to draw into
    MKMapPoint origin = points[0];
    origin.x -= MKMapSizeWorld.width/8.0;
    origin.y -= MKMapSizeWorld.height/8.0;
    MKMapSize size = MKMapSizeWorld;
    size.width /=4.0;
    size.height /=4.0;
    boundingMapRect = (MKMapRect) {origin, size};
    MKMapRect worldRect = MKMapRectMake(0, 0, MKMapSizeWorld.width, MKMapSizeWorld.height);
    boundingMapRect = MKMapRectIntersection(boundingMapRect, worldRect);

    // initialize read-write lock for drawing and updates
    pthread_rwlock_init(&rwLock,NULL);
}
return self;

}

-(void)dealloc{
free(points);
free(velocity);
pthread_rwlock_destroy(&rwLock);
}

//center
-(CLLocationCoordinate2D)coordinate{
return MKCoordinateForMapPoint(points[0]);
}

-(MKMapRect)boundingMapRect{
return boundingMapRect;
}

-(void) lockForReading{
pthread_rwlock_rdlock(&rwLock);
}

-(void) unlockForReading{
pthread_rwlock_unlock(&rwLock);
}

-(MKMapRect)addCoordinate:(CLLocationCoordinate2D)coord{
//Acquire the write lock because we are going to changing the list of points
pthread_rwlock_wrlock(&rwLock);

//Convert a CLLocationCoordinate2D to an MKMapPoint
MKMapPoint newPoint = MKMapPointForCoordinate(coord);
MKMapPoint prevPoint = points[pointCount-1];

//Get the distance between this new point and previous point
CLLocationDistance metersApart = MKMetersBetweenMapPoints(newPoint, prevPoint);
MKMapRect updateRect = MKMapRectNull;

if (metersApart > MINIMUM_DELTA_METERS){
    //Grow the points array if necessary
    if (pointSpace == pointCount){
        pointSpace *= 2;
        points = realloc(points, sizeof(MKMapPoint) * pointSpace);
    }

    //Add the new point to points array
    points[pointCount] = newPoint;
    pointCount++;

    //Compute MKMapRect bounding prevPoint and newPoint
    double minX = MIN(newPoint.x,prevPoint.x);
    double minY = MIN(newPoint.y,prevPoint.y);
    double maxX = MAX(newPoint.x, prevPoint.x);
    double maxY = MAX(newPoint.y, prevPoint.y);

    updateRect = MKMapRectMake(minX, minY, maxX - minX, maxY - minY);
}

pthread_rwlock_unlock(&rwLock);

return updateRect;

}

@end

下面是在mapview上添加PolyLine的方法：([self smoothTrack] 是我针对项目需求做速度平滑渐变的算法，可以忽略；我绘制轨迹的坐标数据结构是由精度、维度、速度构成的字典；最后添加的方法是调用mapview的分类中的方法，所以有级别，也是根我需求相关，可直接用[self.mapView addOverlay:self.polyline] 代替)

NSMutableArray *smoothTrackArray = [self smoothTrack];
double count = smoothTrackArray.count;
CLLocationCoordinate2D points;
float velocity;
points = malloc(sizeof(CLLocationCoordinate2D)count);
velocity = malloc(sizeof(float)count);

for(int i=0;i<count;i++){
    NSDictionary *dic = [smoothTrackArray objectAtIndex:i];
    CLLocationDegrees latitude  = [dic[@"latitude"] doubleValue];
    CLLocationDegrees longitude = [dic[@"longitude"] doubleValue];
    CLLocationCoordinate2D coordinate = CLLocationCoordinate2DMake(latitude, longitude);
    velocity[i] = [dic[@"speed"] doubleValue];
    points[i] = coordinate;
}

self.polyline = [[GradientPolylineOverlay alloc] initWithPoints:points velocity:velocity count:count];
[self.mapView addOverlay:self.polyline level:1];

轨迹添加好了，还需要在渲染器上面呈现，会调用Mapkit相应的代理：(GradientPolylineRenderer 则是与之对应的渲染器)

pragma mark -

pragma mark - MKMap Delegate

import <MapKit/MapKit.h>

@interface GradientPolylineRenderer : MKOverlayPathRenderer

@end
GradientPolylineRenderer.m实现：(上面的几个宏定义，是速度的边界值，以及对应的颜色边界值；另外我这里会对hues[i]是否为0做判断，项目需求要区分暂停点和速度过快点，已防作弊，此种情况会用虚线代替，如果只绘制渐变实线，不用管这)

import "GradientPolylineRenderer.h"

import <pthread.h>

import "GradientPolylineOverlay.h"

import "Constant.h"

define V_MAX 4.5

define V_MIN 1.0

define H_MAX 0.33

define H_MIN 0.03

@implementation GradientPolylineRenderer{
float* hues;
pthread_rwlock_t rwLock;
GradientPolylineOverlay* polyline;
}

-(void) createPath{
CGMutablePathRef path = CGPathCreateMutable();
BOOL pathIsEmpty = YES;
for (int i=0;i< polyline.pointCount;i++){
CGPoint point = [self pointForMapPoint:polyline.points[i]];
if (pathIsEmpty){
CGPathMoveToPoint(path, nil, point.x, point.y);
pathIsEmpty = NO;
} else {
CGPathAddLineToPoint(path, nil, point.x, point.y);
}
}

pthread_rwlock_wrlock(&rwLock);
self.path = path; //<—— don't forget this line.
pthread_rwlock_unlock(&rwLock);

}

//-(BOOL)canDrawMapRect:(MKMapRect)mapRect zoomScale:(MKZoomScale)zoomScale{
// CGRect pointsRect = CGPathGetBoundingBox(self.path);
// CGRect mapRectCG = [self rectForMapRect:mapRect];
// return CGRectIntersectsRect(pointsRect, mapRectCG);
//}

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