FragmentExtension.kt

package <your.package.name>

import androidx.fragment.app.Fragment
import io.flutter.embedding.android.FlutterFragment
import io.flutter.embedding.engine.FlutterEngine

// フラターフラグメントを作成する時にこの関数を使用します。
fun Fragment.createFlutterFragment(flutterFragmentTag: String, flutterCachedEngineId: String, containerId: Int): FlutterFragment {
    var flutterFragment = childFragmentManager.findFragmentByTag(flutterFragmentTag) as FlutterFragment?

    if (flutterFragment == null) {
        var newFlutterFragment = FlutterFragment.withCachedEngine(flutterCachedEngineId).build<FlutterFragment>()

        flutterFragment = newFlutterFragment
        childFragmentManager
            .beginTransaction()
            .add(
                containerId,
                newFlutterFragment,
                flutterFragmentTag
            )
            .commit()
        return flutterFragment
    }
    return flutterFragment
}

// フラター画面を描画する時フラターアプリ内のどこに行くかをこの関数に渡します。
fun Fragment.pushToFlutterFragment(childFragment: Fragment, flutterFragment: FlutterFragment?, flutterRoute: String) {
    if (childFragment == flutterFragment) {
        var cachedEngine: FlutterEngine? = flutterFragment?.flutterEngine
        cachedEngine?.navigationChannel?.pushRoute(flutterRoute);
    }
}