Need help with EventListener.

ricmontalvan · May 12, 2018, 3:17pm

How can I change this statement to be a continues actions instead of tapping.

ship:addEventListener( “tap”, fireLaser )

ex: game starts and the laser automatically begins to fire.

roaminggamer · May 12, 2018, 4:10pm

Don’t use tap events.

Use:

touch event - Superior to tap and flexible.
- my example
  - fires/stop laser
  - creates/destroys laser
  - moves player
enterFrame - to move laser with player if player is moving
finalize - to remove enterframe when player is destroyed.

All functions I used below can be found on or via API page: https://docs.coronalabs.com/api/

May contain typos:

local cx = display.contentCenterX local cy = display.contentCenterY local player = newRect( cx, cy, 20, 20 ) function player.enterFrame( self ) if( not self.laser ) then return end self.laser.x = self.x self.laser.y = self.y end Runtime:addEventListener("enterFrame", player) function player.finalize( self ) Runtime:removeEventListener("enterFrame", self) end player:addEventListener("finalize") function player.touch( self, event ) local eventID = event.id self.x = event.x self.y = event.y if(event.phase == "began") then display.getCurrentStage():setFocus( self, eventID ) self.isFocus = true print("START FIRING") self.laser = display.newRect( self.x, self.y, 6, 1000 ) self.laser.anchorY = 0 self.laser:setFillColor(1,0,0) self:toFront() elseif(target.isFocus ) then if(event.phase == "ended" or event.phase == "cancelled") then display.getCurrentStage():setFocus( self, nil ) self.isFocus = false print( "STOP FIRING" ) display.remove(self.laser) self.laser = nil end end return true end player:addEventListener("touch")

roaminggamer · May 12, 2018, 4:12pm

Tip: I used a rectangle instead of a line for the laser because I knew you ‘might’ want to add a body.

Moving bodies this way isn’t great, but will work OK.

ricmontalvan · May 12, 2018, 4:29pm

Im having a hard time understanding what you posted…

here’s an example of what I’m doing

local function fireLaser() -- Play fire sound! audio.play( fireSound ) local newLaser = display.newImageRect( mainGroup, objectSheet, 5, 14, 40 ) physics.addBody( newLaser, "dynamic", { isSensor=true } ) newLaser.isBullet = true newLaser.myName = "laser" newLaser.x = ship.x newLaser.y = ship.y newLaser:toBack() transition.to( newLaser, { y=-40, time=500, onComplete = function() display.remove( newLaser ) end } ) end

and then

ship:addEventListener( "tap", fireLaser )

Im following the tutorial in the learning section.

I tried understanding what you sent but couldn’t make sense of it.

roaminggamer · May 12, 2018, 5:11pm

Sorry. I’ll let some else follow up on this. I’m not familiar with the tutorials. They are after my time here and I’ve never run through them.

The example I gave you is highly complete, but uses advanced concepts and may not be compatible with the tutorials without changes.

You can remove:

enterframe code
finalize code
player movement in touch
laser creation code in touch

Then, you will be left with a touch listener that knows when to create and destroy a laser.

Hopefully, you can work from there.

function player.touch( self, event ) local eventID = event.id if(event.phase == "began") then display.getCurrentStage():setFocus( self, eventID ) self.isFocus = true print("START FIRING") -- DO START FIRING WORK HERE elseif(target.isFocus ) then if(event.phase == "ended" or event.phase == "cancelled") then display.getCurrentStage():setFocus( self, nil ) self.isFocus = false print( "STOP FIRING" ) -- DO STOP FIRING WORK HERE end end return true end player:addEventListener("touch")

ricmontalvan · May 12, 2018, 5:39pm

I figured it out!!

I tried ship:addEventListener( “touch”, fireLaser ) but all that did was shoot endlessly every time the ship was moved…

The solution was to simply, add a time delay with the **local function fireLaser() **in it.

For anyone that would like to try this here is the set up I had for the tutorial.

local function fireLaser() -- Play fire sound! audio.play( fireSound ) local newLaser = display.newImageRect( mainGroup, objectSheet, 5, 14, 40 ) physics.addBody( newLaser, "dynamic", { isSensor=true } ) newLaser.isBullet = true newLaser.myName = "laser" newLaser.x = ship.x newLaser.y = ship.y newLaser:toBack() transition.to( newLaser, { y=-40, time=500, onComplete = function() display.remove( newLaser ) end } ) end timer.performWithDelay( 500, fireLaser, 0 )

and make sure to delete

ship:addEventListener( “touch”, fireLaser )

ricmontalvan · May 16, 2018, 12:02am

Turns out this method conflicts with the firelaser function . So still looking for a way to make this work.

anon63346430 · May 16, 2018, 12:13am

These questions are so difficult to answer on a forum!

The premise of “tap my ship and fire a single laser” is absolutely a candidate for a tap event. Note the emphasis on single. And tap handler will raise a single event.

Now say you want to simulate continual movement then a tap event is all wrong as @rg points out. For this a touch event combined with enterFrame is the way forward.

Mixing transition and physics is a major no… you want to apply a force to the object (to move it).

There is no “here is the answer” to this kinda problem as the scope is simply massive.

greg_brady · May 17, 2018, 12:12pm

SGS… Don’t I know it!.

ricmontalvan … there’s a few different ways to do this, here is what I use:

every time you fire a laser you add a laser object into a laserObject table.
In your enterframe event handler, you loop through this table and move each laser object one at a time calculating angle, velX and velY
To repeat fire, I do this on a touch event:

if shootTapTimer == nil and cooldownTimer == nil then
shootPrimary()
shootTapTimer = timer.performWithDelay(shootDelay, function() shootPrimary() end ,0)
end

function shootPrimary()

local torpedo = display.newSprite( torpSheet, torpSequence )
   torpedo.objTable = torpedotable
   torpedo.index = #torpedo.objTable + 1
   torpedo.objTable[torpedo.index] = torpedo
   torpedo.id = “torpedo”
   torpedo.range = weaponDischargeRate[1][3]
    torpedo.CvelX = player.velX
   torpedo.CvelY = player.velY

    torpedo.x =player.x + 50 * math.cos((player.rotation)* (mPi/180))
   torpedo.y= player.y + 50 * math.sin((player.rotation)* (mPi/180))

and in my event loop I calculate velX and velY:

   local accel = 5
   local tangle = torpedotable[i].rotation   * -1
   torpedotable[i].CvelX = torpedotable[i].CvelX + math.sin(math.rad(tangle)) * (accel)
   torpedotable[i].CvelY = torpedotable[i].CvelY + math.cos(math.rad(tangle)) * (accel)
   local spd = math.abs(torpedotable[i].CvelX) + math.abs(torpedotable[i].CvelY)

ricmontalvan · May 18, 2018, 10:30pm

I’m going to have to learn a bit more of the basics before I integrate this into my app 🤷

roaminggamer · May 12, 2018, 4:10pm