Kotlin：实例化类中变量的未解析引用

Question

I make an ear training app and want the levels to be customizable. So I have a class with the same function for each of the 12 tones, so imagine setDb, setD, setEb etc.:

class MakeLevel(context: Context) {
    fun setC(something: Boolean): Boolean {
        var c = something
        return c
    }

I then instantiate the class in my main activity (FullscreenActivity):

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_fullscreen)
    makeLevel = MakeLevel(this)
}
companion object {
    lateinit var makeLevel: MakeLevel
}

Then in the fragment where the levels are selected, I do this:

override fun onResume() {
    super.onResume()
    majpentlevelbutton.setOnClickListener { view ->
        FullscreenActivity.makeLevel.setC(true)
        // [same for setD, setE, setG and setA, and false for all the other notes]
        view.findNavController().navigate(R.id.action_levelSelectFragment_to_chromaticFragment)
    }
}

Now here comes my problem: I want to access the value of c to determine whether ther sounds and the button for c should be loaded or not, and I can´t find a way to do so. For example, I´d like to use it like this:

if (c == true) {
    c_button.visibility = View.VISIBLE
}
else {
    c_button.visibility = View.GONE
}

I´ve tried c , makeLevel.c , FullscreenActivity.makeLevel.c and many more. Every time I get an Unresolved reference . So my question is how do I get a reference on the var c?

Answer 1

So far c is only a local variable within the method setC . If you need the value outside of the method you need to define a property:

class MakeLevel(context: Context) {
    var c = initValue
    fun setC(something: Boolean){
        c = something
    }
}

Now you can access this variable with: FullscreenActivity.makeLevel.c

Answer 2

Your problem is that you are trying to access a variable outside of its scope.

 class MakeLevel(context: Context) { private var c = initValue fun setC(something: Boolean){ c = something } fun getC(something: Boolean) { return c } if (getC() == true) c_button.visibility = View.VISIBLE else c_button.visibility = View.GONE }