Kotlin中使用不同构造函数构建时如何复用重写方法？

你可以通过抽离回调核心逻辑，再根据API版本包装对应构造的NetworkCallback来避免重复代码，只需要写一次重写方法的核心实现。

实现方案 #

先把onCapabilitiesChanged的业务逻辑抽成独立实现，再根据API版本选择对应的构造函数创建NetworkCallback实例，复用同一套逻辑：

val cm = getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager

// 抽离核心回调逻辑
val coreCallback = object : NetworkCallback() {
    override fun onCapabilitiesChanged(network: Network, networkCapabilities: NetworkCapabilities) {
        super.onCapabilitiesChanged(network, networkCapabilities)
        val ssid =
            if (Build.VERSION.SDK_INT >= 29) {
                (networkCapabilities.transportInfo as WifiInfo).ssid
            }
            else {
                (applicationContext?.getSystemService(Context.WIFI_SERVICE) as WifiManager).connectionInfo.ssid
            }
        Log.d(TAG, "onCapabilitiesChanged network: $network ssid: $ssid")
    }
}

// 根据API版本选择对应构造的NetworkCallback并注册
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.S) {
    cm.registerDefaultNetworkCallback(object : NetworkCallback(FLAG_INCLUDE_LOCATION_INFO) {
        override fun onCapabilitiesChanged(network: Network, networkCapabilities: NetworkCapabilities) {
            coreCallback.onCapabilitiesChanged(network, networkCapabilities)
        }
    })
} else {
    cm.registerDefaultNetworkCallback(coreCallback)
}

更简洁的封装写法 #

如果需要多次使用该回调，可以把逻辑封装成函数，进一步简化调用：

private fun buildNetworkCallback(): NetworkCallback {
    val coreLogic = { network: Network, capabilities: NetworkCapabilities ->
        val ssid =
            if (Build.VERSION.SDK_INT >= 29) {
                (capabilities.transportInfo as WifiInfo).ssid
            }
            else {
                (applicationContext?.getSystemService(Context.WIFI_SERVICE) as WifiManager).connectionInfo.ssid
            }
        Log.d(TAG, "onCapabilitiesChanged network: $network ssid: $ssid")
    }

    return if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.S) {
        object : NetworkCallback(FLAG_INCLUDE_LOCATION_INFO) {
            override fun onCapabilitiesChanged(network: Network, networkCapabilities: NetworkCapabilities) {
                super.onCapabilitiesChanged(network, networkCapabilities)
                coreLogic(network, networkCapabilities)
            }
        }
    } else {
        object : NetworkCallback() {
            override fun onCapabilitiesChanged(network: Network, networkCapabilities: NetworkCapabilities) {
                super.onCapabilitiesChanged(network, networkCapabilities)
                coreLogic(network, networkCapabilities)
            }
        }
    }
}

// 调用时
val cm = getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
cm.registerDefaultNetworkCallback(buildNetworkCallback())

这种方式既保证了不同API版本使用对应的构造函数，又只维护一套核心业务逻辑，避免了代码冗余。

内容的提问来源于stack exchange，提问作者theblitz