写一个基类如Base.php，通过其_initialize来实现，如：

<?php
namespace app\admin\controller;

use think\Controller;

class Base extends Controller{
    public function _initialize(){
        $uid = session('uid');
        if($uid == null){
            $this->rediect('Login/index','请先登录后操作');
        }
    }
}

其中Login.php不能继承Base.php，否则需要另外的特殊判断，如：

<?php
namespace app\admin\controller;

use think\Controller;

class Login extends Controller{
    public function _initialize(){
        $uid = session('uid');
        if($uid != null){
            $this->rediect('Index/index','已登录');
        }
    }
}