Android Native achieve immersive Immersion

package com.example.immersion;

import androidx.appcompat.app.ActionBar;
import androidx.appcompat.app.AppCompatActivity;

import android.graphics.Color;
import android.os.Build;
import android.os.Bundle;
import android.view.View;

public class BaseActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_base);
        initTransparentStatusBar();
    }

    /**
     * 状态栏透明
     * 如果只是显示透明的状态栏，只需要实行initTransparentStatusBar这方法
     */
    private void initTransparentStatusBar() {
        if (Build.VERSION.SDK_INT >= 21) {
            View decorView = getWindow().getDecorView();
            int option = View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN |
                    View.SYSTEM_UI_FLAG_LAYOUT_STABLE;
            decorView.setSystemUiVisibility(option);
            getWindow().setStatusBarColor(Color.TRANSPARENT);
        }
        ActionBar actionBar = getSupportActionBar();
        actionBar.hide();
    }

    /**
     * 真正的沉浸式
     * 如果只是设置这个方法，ActionBar会显示，然后隐藏
     * 所以如果要完全沉浸式，initTransparentStatusBar，onWindowFocusChanged
     * 两个方法都要实现;
     *
     * @param hasFocus
     */
    @Override
    public void onWindowFocusChanged(boolean hasFocus) {
        super.onWindowFocusChanged(hasFocus);
        if (hasFocus && Build.VERSION.SDK_INT >= 19) {
            View decorView = getWindow().getDecorView();
            int option = View.SYSTEM_UI_FLAG_LAYOUT_STABLE |
                    View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION |
                    View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN |
                    View.SYSTEM_UI_FLAG_HIDE_NAVIGATION |
                    View.SYSTEM_UI_FLAG_FULLSCREEN |
                    View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY;
            decorView.setSystemUiVisibility(option);
        }
    }
}