react-native-navigation/android/app/src/main/java/com/reactnativenavigation/NavigationActivity.java

package com.reactnativenavigation;

import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.view.View;

import com.facebook.react.modules.core.DefaultHardwareBackBtnHandler;

public class NavigationActivity extends AppCompatActivity implements DefaultHardwareBackBtnHandler {
    private View contentView;

    @Override
    public void setContentView(View contentView) {
        super.setContentView(contentView);
        this.contentView = contentView;
    }

    @Nullable
    public View getContentView() {
        return contentView;
    }

    @Override
    public void invokeDefaultOnBackPressed() {
        onBackPressed();
    }
}