错误：无法在视图目录中查找视图“索引”

Question

我正在使用Express应用程序，但始终出现以下错误： 错误：无法在视图目录中查找视图“索引”。 我通过npm安装路径，并在server.js中需要它，但我仍然面临相同的错误。 如何解决此问题？感谢您的输入。

server.js：

  

    var express = require("express");
    var path = require('path');
    var bodyParser = require("body-parser");
    var methodOverride = require('method-override');
    var PORT = process.env.PORT || 8081;

    var app = express();

    // serve static content for the app and set up body-parser
    app.use(express.static(__dirname+'/public'));
    app.use(bodyParser.urlencoded({
      extended: false
    }));
    app.use(bodyParser.json());
    app.use(methodOverride('_method'));

    // set up Handlebars
    var exphbs = require("express-handlebars");
    app.engine("handlebars", exphbs({
      defaultLayout: "main"
    }));

    // app.set('views', path.join(__dirname, 'views'));
    app.set("view engine", "handlebars");

    // Import routes and give the server access to them
    var routes = require("./controllers/routes.js");
    app.use('/',routes);

    // start the server listening
    app.listen(PORT, function() {
      console.log("App now listening at localhost:" + PORT);
    });

routes.js：

var express = require('express');
var router = express.Router();

// Import the model to use its database functions.
var burger = require('../models/burger.js');

router.get('/', function(req, res) {
	burger.all(function(burger_data){

		 console.log(burger_data);
		 res.render('index', {burger_data});

	});
  });

router.post('/burgers/create',function(req,res){
	burger.create(req.body.burger_name, function(result){
		res.redirect('/');
	});
});

router.put('/burgers/update',function(req,res){
	burger.update(req.body.burger_id, function(result){
		console.log(result);
		res.redirect('/');
	});
});

module.exports = router;