昨天宪迟，寫B(tài)aseApplication時候，一些“靜態(tài)方法、屬性”都放在companion object(ps:kotlin 根本沒有靜態(tài)這個概念躲舌，而伴生對象本身是一個單例對象会通，kotlin的字節(jié)碼中可以看到)中口予，MyApplication繼承BaseApplication了

//基類
open class BaseApplication : MultiDexApplication() {
    init {
        initInstance()
    }

    private fun initInstance() {
        instance = this
    }

    override fun onCreate() {
        super.onCreate()
        //instance = this

        mainThreadHandler = Handler(Looper.getMainLooper())
        mainThreadId = Process.myTid()
    }

    companion object {
        lateinit var instance: BaseApplication

        private var mainThreadHandler: Handler? = null
        private var mainThreadId: Int? = 0

        /** 上下文(Application) */
        fun getContext(): Context {
            return instance.applicationContext
        }

        /** 主線程Handler */
        fun getMainHandler(): Handler {
            return mainThreadHandler!!
        }

        /** 主線程Id */
        fun getMainThreadId(): Int {
            return mainThreadId!!
        }
    }
}
//子類
class MyApplication: BaseApplication()

如果你想子類調(diào)用BaseApplication中的“靜態(tài)方法”，如：

MyApplication.getContext() // wrong

發(fā)現(xiàn)只能用父類名.getContext()涕侈，說明 kotlin 的“靜態(tài)” 不能被子類繼承沪停，順便翻墻查了一下，然后裳涛，改造代碼：

//基類
open class BaseApplication : MultiDexApplication() {
    init {
        initInstance()
    }

    private fun initInstance() {
        instance = this
    }

    override fun onCreate() {
        super.onCreate()
        //instance = this

        mainThreadHandler = Handler(Looper.getMainLooper())
        mainThreadId = Process.myTid()
    }

    companion object {
        lateinit var instance: BaseApplication

        private var mainThreadHandler: Handler? = null
        private var mainThreadId: Int? = 0

        /** 上下文(Application) */
        fun getContext(): Context {
            return instance.applicationContext
        }

        /** 主線程Handler */
        fun getMainHandler(): Handler {
            return mainThreadHandler!!
        }

        /** 主線程Id */
        fun getMainThreadId(): Int {
            return mainThreadId!!
        }
    }

    open class BaseApplicationCompanion {
        open fun getContext() : Context = BaseApplication.getContext()
        open fun getMainHandler() : Handler = BaseApplication.getMainHandler()
        open fun getMainThreadId() : Int = BaseApplication.getMainThreadId()
    }
}
//子類
class MyApplication: BaseApplication() {

    companion object : BaseApplicationCompanion()
}

ps：kotlin的伴生對象是可以繼承于另一個類
另外木张，一個(非單獨(dú))伴生對象不能繼承另外一個(非單獨(dú))伴生對象，如圖：

companion object

最后端三，貼出kotlin的字節(jié)碼（說明伴生對象就是一個靜態(tài)內(nèi)部類）

伴生對象.jpg