代码之家 › 专栏 › 技术社区 › Nat

打开自定义属性以更改MGLSymbolStyleLayer的图像

mapbox swift objective-c ios

Nat · 技术社区 · 6 年前

typedef NS_ENUM(NSInteger, MyType) {
    MyTypeUnknown = 0,
    MyTypeOne,
    MyTypeTwo,
};

我有一个非群集管脚图层:

MGLSymbolStyleLayer *markerLayer = [[MGLSymbolStyleLayer alloc] initWithIdentifier:@"markerLayerId" source:source];
markerLayer.predicate = [NSPredicate predicateWithFormat:@"cluster != YES"];
[style addLayer: markerLayer];

我知道我想添加基于 type 别针的。我唯一确定的是我需要将这些图像添加到图层:

[style setImage:[UIImage imageNamed:@"img0"] forName:@"img0id"];
[style setImage:[UIImage imageNamed:@"img1"] forName:@"img1id"];
[style setImage:[UIImage imageNamed:@"img2"] forName:@"img2id"];

现在我应该设置名称,但我不确定如何设置:

markerLayer.iconImageName = [NSExpression expressionForConstantValue:@"???"]; // or withFormat..?

@objc class MyPointFeature: MGLPointFeature {
    @objc var type: MyType = .unknown
}

我真的不知道怎么打开它属性设置管脚的图像。有什么帮助吗?

0 回复 | 直到 6 年前

Nat 6 年前

首先,我们需要一个变量,它可以用来访问值。为了使其更具可读性,让我们为我们的需要创建一个变量(稍后,例如在选择一个管脚时)和MapBox需要的条目立即创建:

@objc class MyPointFeature: MGLPointFeature {
    @objc var type: MyType = .unknown {
        didSet {
            self.attributes = ["myType": MyPointFeature .staticTypeKey(dynamicType: type)]
        }
    }

    // This is made without dynamic property name to string cast, because
    // the values shouldn't be changed so easily and a developer without
    // suspecting it's a key somewhere could accidentally create a bug
   // PS. if you have swift-only code, you can make it in MyType enum
   @objc static func staticTypeKey(dynamicType: MyType) -> String {
        switch dynamicType {
        case .one:
            return "one"
        case .two:
            return "two"
        default:
            return "unknown"
        }
    }
}

现在我们要将图像名称注册到给定的密钥:

[style setImage:[UIImage imageNamed:@"img0"] forName:@"img0Key"];
[style setImage:[UIImage imageNamed:@"img1"] forName:@"img1Key"];
[style setImage:[UIImage imageNamed:@"img2"] forName:@"img2Key"];

最后,让我们使用先前指定的属性绑定图像名称键:

NSDictionary *typeIcons = @{[MyPointFeature staticTypeKeyWithDynamicType:MyTypeUnknown]: @"img0Key",
                            [MyPointFeature staticTypeKeyWithDynamicType:MyTypeOne]: @"img1Key",
                            [MyPointFeature staticTypeKeyWithDynamicType:MyTypeTwo]: @"img2Key"};
myLayer.iconImageName = [NSExpression expressionWithFormat:@"FUNCTION(%@, 'valueForKeyPath:', myType)", typeIcons];