CoronaLabs物理游戏中为Box添加addEventListener的位置疑问

嘿，我完全懂你作为新手的困惑——刚把物理游戏的基础内容搭好，却不知道该把点击事件监听器放在哪儿才能让Box有反应。别担心，我来一步步帮你搞定这个问题：

核心思路 #

在Corona里，要让物理对象响应点击，你需要把**触摸/点击监听器直接绑定到目标对象（也就是你的Box）**上，而且要确保在对象创建完成后再添加监听器，同时要贴合场景的生命周期逻辑。

具体修改步骤 #

• 编写点击事件处理函数：定义点击Box后要执行的操作（比如施加冲量、销毁对象或者更新点击计数）。
• 给Box绑定监听器：在Box对象创建并添加物理属性后，把监听器挂载到它上面。
• （可选但重要）规范tapText的管理：你原来的tapText在场景函数外，场景切换时可能无法被正确清理，最好把它移到create函数里并加入场景组。

修改后的完整代码 #

我已经给你的level1.lua做了针对性修改，关键改动都加了注释：

require("toast")
local composer = require( "composer" )
local scene = composer.newScene()
-- include Corona's "physics" library
local physics = require("physics")
--------------------------------------------
local tapCount = 0
local tapText -- 先声明变量，后续在create中初始化
--------------------------------------------
local screenW, screenH, halfW = display.actualContentWidth, display.actualContentHeight, display.contentCenterX

function scene:create( event )
    local sceneGroup = self.view

    physics.start()
    physics.pause()

    local background = display.newImageRect("game-background.png", 1170, 658)
    background.x = display.contentCenterX
    background.y = display.contentCenterY

    -- 将tapText移到create内创建，方便加入场景组统一管理
    tapText = display.newText( tapCount, display.contentCenterX, 20, native.systemFont, 40 )

    -- OFFSCREEN BOX, position it, and rotate slightly
    local box = display.newImageRect( "box.png", 40, 40 )
    box.x, box.y = 160, -100
    box.rotation = 33

    -- add physics
    physics.addBody( box, { density=1.0, friction=0.3, bounce=0.2 } )

    -- 1. 定义Box的点击处理函数
    local function onBoxTap( event )
        -- 给Box施加向上的冲量，event.target就是被点击的Box对象
        event.target:applyLinearImpulse( 0, -0.25, event.target.x, event.target.y )
        -- 如果需要点击后销毁Box，取消下面这行注释即可
        -- display.remove(event.target)
        
        -- 更新点击计数文本
        tapCount = tapCount + 1
        tapText.text = tapCount
        return true -- 阻止事件向下层对象传递
    end

    -- 2. 给Box绑定tap事件监听器
    box:addEventListener( "tap", onBoxTap )

    -- create a grass object and add physics (with custom shape)
    local grass = display.newImageRect( "grass.png", screenW, 82 )
    grass.anchorX = 0
    grass.anchorY = 1
    -- draw the grass at the very bottom of the screen
    grass.x, grass.y = display.screenOriginX, display.actualContentHeight + display.screenOriginY
    local grassShape = { -halfW,-34, halfW,-34, halfW,34, -halfW,34 }
    physics.addBody( grass, "static", { friction=0.3, shape=grassShape } )

    -- 3. 将所有显示对象加入场景组，包括tapText
    sceneGroup:insert( background )
    sceneGroup:insert( grass )
    sceneGroup:insert( box )
    sceneGroup:insert( tapText )
end

function scene:show( event )
    local sceneGroup = self.view
    local phase = event.phase

    if phase == "will" then
        -- Called when the scene is still off-screen and is about to move on screen
    elseif phase == "did" then
        -- Called when the scene is now on-screen
        physics.start()
    end
end

function scene:hide( event )
    local sceneGroup = self.view
    local phase = event.phase

    if event.phase == "will" then
        -- Called when the scene is on-screen and is about to move off-screen
        physics.stop()
    elseif phase == "did" then
        -- Called when the scene is now off-screen
    end
end

function scene:destroy( event )
    -- Called prior to the removal of scene's "view" (sceneGroup)
    local sceneGroup = self.view

    package.loaded[physics] = nil
    physics = nil
end

---------------------------------------------------------------------------------
-- Listener setup
scene:addEventListener( "create", scene )
scene:addEventListener( "show", scene )
scene:addEventListener( "hide", scene )
scene:addEventListener( "destroy", scene )
-----------------------------------------------------------------------------------------
return scene

为什么之前的尝试没成功？ #

大概率是因为你没有把监听器直接绑定到Box对象上，而是误加到了场景或其他无关对象上；或者是监听器添加的时机不对（比如在Box还没创建完成时就绑定了）。上面的代码里，我们在Box创建并添加物理属性后立刻绑定监听器，确保对象已经存在，这样点击就能正常触发响应了。

内容的提问来源于stack exchange，提问作者Ecodor