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我有一个要保存到 plist 的自定义 NSObject 类 Trails。我现在可以正确保存和加载它，除了一部分。我在那个类中有一个自定义的 MKOverlay 类对象 Crumbs，我也想保存它。由于 crumbs 符合 NSCoding，因此不会引发错误，但是在保存并重新打开应用程序后，叠加层不会显示在地图上。crumb 对象不是 nil，但仍然不显示。

轨迹.h

@interface Trails : NSObject <NSCoding>
{
    @public
    int topSpeed;
    float avgSpeed;
}
@property (nonatomic, strong) NSString *miles;
@property (nonatomic, strong) NSDate *date;
@property (nonatomic, strong) NSString *time;
@property (nonatomic, strong) CrumbPath *crumbs;
- (NSString *)displayDate;
- (NSString *)displayStartTime;
- (void)addTopSpeed: (int)top withAvgSpeed:(float)avg;
@end

轨迹.m

- (void)encodeWithCoder:(NSCoder *)coder {
    [coder encodeObject:miles forKey:@"miles"];
    [coder encodeObject:date forKey:@"date"];
    [coder encodeObject:time forKey:@"time"];
    [coder encodeObject:crumbs forKey:@"crumbs"];
    [coder encodeFloat:avgSpeed forKey:@"avgSpeed"];
    [coder encodeInt:topSpeed forKey:@"topSpeed"];

}


- (id)initWithCoder:(NSCoder *)coder {
    self = [super init];
    if( self != nil )
    {
        miles = [coder decodeObjectForKey:@"miles"];
        date = [coder decodeObjectForKey:@"date"];
        time = [coder decodeObjectForKey:@"time"];
        crumbs = [coder decodeObjectForKey:@"crumbs"];
        avgSpeed = [coder decodeFloatForKey:@"avgSpeed"];
        topSpeed = [coder decodeIntForKey:@"topSpeed"];
    }
    return self;
}

面包屑.h

@interface CrumbPath : NSObject <MKOverlay, NSCoding>

面包屑.m

#import "CrumbPath.h"

#define INITIAL_POINT_SPACE 1000
#define MINIMUM_DELTA_METERS 10.0

@implementation CrumbPath

@synthesize points, pointCount;

- (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;
}

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

- (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 be 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 the 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 the 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;
}

//Conform to NSCoding
- (void)encodeWithCoder:(NSCoder *)coder {
    //I think I need to do something here?
}


- (id)initWithCoder:(NSCoder *)coder {
    self = [super init];
    if( self != nil )
    {
        //I think I need to do something here?
    }
    return self;
}

@end
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1 回答 1

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你的类encodeWithCoder和类的实现是空的。您需要保存所有属性/变量，就像您为对象所做的一样。所有对象都负责保存自己的关于 NSCoding 的属性/变量。initWithCoderCrumbPathTrails

只是补充一下-您不能直接将 CLLocationCoordinate2D 和 CGRect 写入磁盘。您必须将它们分解并重组。例如，使用 CGRect，您必须进行如下编码：

 [aCoder encodeFloat:rect.origin.x forKey:@"x"];
 [aCoder encodeFloat:rect.origin.y forKey:@"y"];
 [aCoder encodeFloat:rect.size.width forKey:@"width"];
 [aCoder encodeFloat:rect.size.height forKey:@"height"];

然后在解码/初始化时，你必须重构它：

 CGFloat x = [aDecoder decodeFloatForKey:@"x"];
 CGFloat y = [aDecoder decodeFloatForKey:@"y"];
 CGFloat width = [aDecoder decodeFloatForKey:@"width"];
 CGFloat height = [aDecoder decodeFloatForKey:@"height"];

 self.rect = CGRectMake(x,y,width,height);
于 2013-04-08T21:09:30.660 回答