javascript - 未捕获的类型错误 : Cannot read property 'add' of null phaser

Question

下面是菜单所在的代码的简化版本。我不断收到此错误。当我单击播放按钮时会发生此错误:

Uncaught TypeError: Cannot read property 'add' of null

我知道那是当我检查 Sprite 播放是否被点击但无法找出问题时。

这是图片:

JsFiddle Format

  preload: function() {
                game.load.image('background', 'http://s1.postimg.org/nqynk9tkv/starfield.png')
                game.load.image('play-back', 'http://icon-park.com/imagefiles/movie_play_black.png');

            },
            create: function() {
                this.backgroundImg = this.game.add.tileSprite(0, 0, 500, 550, 'background')

                this.gameText = game.add.text(game.world.centerX-190, game.world.centerY - 150, "Space Invaders", {
            font: "60px Times New Roman",
            fill: "#ccccb3",
            fontWeight: "bold",
            stroke: "white",
            strokeThickness: 2.5
        });

 /*       // this.gameText.anchor.setTo(0.5)
        this.gameText.angle =
*/
        play = game.add.sprite(120,280,'play-back')
        play.scale.setTo(0.5);
         game.physics.arcade.enable(play);
        play.events.onInputDown.add(this.start, this);

            },
            update: function() {
                this.backgroundImg.tilePosition.y += 5;


            },
            render: function() {

            },
            start: function() {

                game.start.main('main')
            }

        };

Answer 1

来自移相器文档:"The Input-related events will only be dispatched if the Sprite has had inputEnabled set to true"