@Override
    protected void onCreate(Bundle savedInstanceState) {
        ······
        //拿到标题栏
        ActionBar actionBar = getSupportActionBar();
        //显示左上角箭头返回
        actionBar.setDisplayHomeAsUpEnabled(true);

        //为标题设置显示图标
        actionBar.setDisplayShowHomeEnabled(true);
        //设置图标
        actionBar.setLogo(R.drawable.ic_baseline_settings_24);
        //显示Logo
        actionBar.setDisplayUseLogoEnabled(true);
    }

//选中哪一项执行哪一项的操作
    @Override
    public boolean onOptionsItemSelected(@NonNull MenuItem item) {
        //拿到每一项的Id
        int itemId = item.getItemId();
        switch (itemId){
           ······
            case android.R.id.home:
                //销毁当前页面 实现返回
                this.finish();
                break;
        }
        return super.onOptionsItemSelected(item);
    }