FragmentでBackPressedを捕る取る採る盗る

FragmentでBackPressedを捕る

FragmentOnBackPressed.kt

fun View.catchBackPressed(vararg listener: FragmentOnBackPressed) {
    requestFocus()
    setOnKeyListener { _, k, e ->
        if (k == KeyEvent.KEYCODE_BACK && e.action == KeyEvent.ACTION_UP) {
            listener.any { it.onBackPressed() }
        } else {
            false
        }
    }
}

interface FragmentOnBackPressed {
    fun onBackPressed(): Boolean
}

AppFragment.kt

class AppFragment: Fragment(), FragmentOnBackPressed {

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        view.catchBackPressed(this)
    }

    override fun onBackPressed(): Boolean {
        return if (flag) {
            some()
            true
        } else {
            false
        }
    }

}

仕様

View.setOnKeyListenerの中でlistener.any { it.onBackPressed() }としているので、trueを返すとそれ以降のonBackPressedを呼び出しましぇん。
つまり...

MyFragment.kt

class MyFragment: Fragment(), FragmentOnBackPressed {

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        val viewModel = ViewModelproviders.of(this).get(MyViewModel::class.java)
        view.catchBackPressed(viewModel, this)
    }

    override fun onBackPressed(): Boolean {
        some()
        return true

    }
}

class MyViewModel: ViewModel(), FragmentOnBackPressed {

    override fun onBackPressed(): Boolean {
        someModel()
        return true
    }

}

とすると、MyFragmentのonBackPressedは絶対に呼ばれないですね！