Inspired by https://speakerdeck.com/magiepooh/how-to-get-size-of-navigationbar-and-statusbar

WindowInsetsSubject.java

package com.wantedly.android.namecard_scanner.utils;

import android.support.v4.view.OnApplyWindowInsetsListener;
import android.support.v4.view.ViewCompat;
import android.support.v4.view.WindowInsetsCompat;
import android.view.View;

import rx.Observable;
import rx.subjects.BehaviorSubject;

/**
 * These codes are licensed under CC0.
 * <p/>
 * Created by cattaka on 2016/10/13.
 */

public class WindowInsetsSubject {
    private OnApplyWindowInsetsListener mOnApplyWindowInsetsListener = new OnApplyWindowInsetsListener() {
        @Override
        public WindowInsetsCompat onApplyWindowInsets(View v, WindowInsetsCompat insets) {
            mBehaviorSubject.onNext(insets);
            return insets;
        }
    };

    private BehaviorSubject<WindowInsetsCompat> mBehaviorSubject;

    public WindowInsetsSubject() {
        mBehaviorSubject = BehaviorSubject.create();
    }

    public void attachView(View view) {
        ViewCompat.setOnApplyWindowInsetsListener(view, mOnApplyWindowInsetsListener);
    }

    public Observable<WindowInsetsCompat> observable() {
        return mBehaviorSubject;
    }
}