案例展示

原理分析

代码实现

• Observer 接口

//观察者接口，由观察者来实现
interface Observer {
    fun update(temperatrue: Float?, pressure: Float?, humidity: Float?)
}

• Observer 接口的实现

class CurrentConditions : Observer {

    var temperatrue: Float? = null
    var pressure: Float? = null
    var humidity: Float? = null

    override fun update(temperatrue: Float?, pressure: Float?, humidity: Float?) {
        this.temperatrue = temperatrue
        this.pressure = pressure
        this.humidity = humidity
        display()
    }

    fun display() {
        println("Temperatrue: $temperatrue , Pressure: $pressure , Humidity: $humidity")
    }
}

•  Subject 接口

interface Subject {
    fun registerObserver(o: Observer)
    fun removeObserver(o: Observer)
    fun notifyObservers()
}

•  Subject 接口的实现

class WeatherData : Subject {

    var temperatrue: Float? = null
    var pressure: Float? = null
    var humidity: Float? = null
    val observers: MutableList<Observer> = ArrayList()

    override fun registerObserver(o: Observer) {
        if (!observers.contains(o)) {
            observers.add(o)
        }
    }

    override fun removeObserver(o: Observer) {
        if (observers.contains(o)) {
            observers.remove(o)
        }
    }

    override fun notifyObservers() {
        observers.forEach {
            it.update(temperatrue, pressure, humidity)
        }
    }

    fun setData(temperatrue: Float?, pressure: Float?, humidity: Float?) {
        this.temperatrue = temperatrue
        this.pressure = pressure
        this.humidity = humidity
        notifyObservers()
    }
}

• 调用代码

fun main() {
    val currentConditions = CurrentConditions()
    val weatherData = WeatherData()
    weatherData.registerObserver(currentConditions)

    weatherData.setData(10F, 20F, 30F)
}

• 效果展示