这里应该传递什么上下文?

I have a Chronometer class with the following parameters

open class Chronometer @JvmOverloads constructor(context: Context?,
attrs: AttributeSet? = null, 
defStyle: Int = 0)

And a MyHandler class that calls 2 methods from the Chronometer class. For that, I need to pass a Context, but I don't know what context should it be.

class MyHandler(activity: Chronometer?) : Handler() {

    Chronometer(CONTEXT HERE).updateText(SystemClock.elapsedRealtime())
    Chronometer(CONTEXT HERE).dispatchChronometerTick()

    sendMessageDelayed(
    Message.obtain(this, TICK_WHAT), 0)
}

I have tried ChronoFragment().context (ChronoFragment is a fragment class), MainActivity().applicationContext and MainActivity().baseContext but all of those throw a NullPointerException:

Attempt to invoke virtual method 'android.content.res.Resources
android.content.Context.getResources()' on a null object reference

那么,这里传递的上下文应该是什么?谢谢。