object:applyForce problem

Getting Started Newbie Questions
#21

@Roaminggamer, I mean where to put that function? By just calling it and can use or need to put inside some enterFrame listener to use it? 

#22

If you use setLinearVelocity() be sure to later set the velocity to zero or it will keep moving forever.

i.e.  instead of using a enterFrame() with a force, do the following:

  1. Where you used to ‘attach’ (start listening for) enterFrame, setLinearVelocity(0,-400) like you showed above.
  2. Where you used to ‘detach’ (stop listening for) enterFrame, setLinearVelocity(0,0)
#23

I would add a enterFrame listener to the player (xxx) and have it run forever.  Then, in the enterFrame listener put a derivative of the code I wrote.

It is very brute force, but will keep the object on screen.

#24

Note: For ‘jumping’, applyLinearImpulse() is more suitable than velocity or force.

#25

I write like

local function jumperOnScreen(self, event) &nbsp; print(string.format("Game Scene: X: %d, Y: %d", self.x, self.y)) &nbsp; &nbsp;buffer = buffer or 0 &nbsp; &nbsp;local minX = display.contentCenterX - display.actualContentWidth/2 + self.contentWidth/2 + buffer &nbsp; &nbsp;local maxX = display.contentCenterX + display.actualContentWidth/2 - self.contentWidth/2 - buffer &nbsp; &nbsp;local minY = display.contentCenterY - display.actualContentHeight/2 + self.contentHeight/2 + buffer &nbsp; &nbsp;local maxY = display.contentCenterY + display.actualContentHeight/2 - self.contentHeight/2 - buffer &nbsp; &nbsp;if( self.x \< minX ) then self.x = minX end &nbsp; &nbsp;if( self.x \> maxX ) then self.x = maxX &nbsp;end &nbsp; &nbsp;if( self.y \< minY ) then self.y = minY end &nbsp; &nbsp;if( self.y \> maxY ) then self.y = maxY end end

jumper.enterFrame =&nbsp; &nbsp; &nbsp; &nbsp; function(self, event) &nbsp; &nbsp; &nbsp; &nbsp; -- self:applyForce(0 \* self.mass, -200 \* self.mass, self.x, self.y) &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; -- jumper:setLinearVelocity(0, -400) -- Jumper is jumping with -300 to jumper.y &nbsp; &nbsp; &nbsp; &nbsp; jumper:applyLinearImpulse(0, -200, jumper.x, jumper.y) &nbsp; &nbsp; &nbsp; &nbsp; jumperOnScreen(jumper) &nbsp; &nbsp; &nbsp; end

For every time, it doesn’t go beyond the minY, but for MaxY, it goes beyond the screen. So when I jump, it is not going beyond the roof but it can goes until the bottom and cannot see it anymore

#26

No.  Don’t put an impulse in an enterFrame call.  That isn’t what I suggested.

Give me 10 and I’ll post an example.

** UPDATE ** 10 minutes

#27

This is how I wrote for the function. It is still not working for my project though I think I need to call this function inside some functions or?? :smiley:

 minX = 50 &nbsp; maxX = display.contentWidth &nbsp; minY = 50 &nbsp; maxY = display.contentHeight - 150 &nbsp;&nbsp; &nbsp; -- checks the x = 0 &nbsp; if self.x - self.width \* 0.5 \< minX then &nbsp; &nbsp; self.x = minX &nbsp; &nbsp;&nbsp; &nbsp; elseif self.x - self.width \* 0.5 \> maxX then &nbsp; &nbsp; self.x = maxX &nbsp; &nbsp;&nbsp; &nbsp; elseif self.y - self.height \* 0.5 \< minY then self.y = minY &nbsp; &nbsp;&nbsp; &nbsp; elseif self.y - self.height \* 0.5 \> maxY then &nbsp; &nbsp; self.y = maxY
#28

Gives you 10 bucks or 10 minutes?? :smiley:

#29

Here look at this example:

http://github.com/roaminggamer/RG_FreeStuff/raw/master/AskEd/2016/05/jump.zip

-- ============================================================= -- Your Copyright Statement Goes Here -- ============================================================= -- main.lua -- ============================================================= -- Empty Framework - Generated using 'EAT - Frameworks' -- https://gumroad.com/l/EATFrameOneTime -- ============================================================= io.output():setvbuf("no") display.setStatusBar(display.HiddenStatusBar) local function stayOnScreen( obj ) buffer = buffer or 0 local minX = display.contentCenterX - display.actualContentWidth/2 + obj.contentWidth/2 + buffer local maxX = display.contentCenterX + display.actualContentWidth/2 - obj.contentWidth/2 - buffer local minY = display.contentCenterY - display.actualContentHeight/2 + obj.contentHeight/2 + buffer local maxY = display.contentCenterY + display.actualContentHeight/2 - obj.contentHeight/2 - buffer local correctedX = false local correctedY = false if( obj.x \< minX ) then obj.x = minX; correctedX = true end if( obj.x \> maxX ) then obj.x = maxX; correctedX = true end if( obj.y \< minY ) then obj.y = minY; correctedY = true end if( obj.y \> maxY ) then obj.y = maxY; correctedY = true end local vx,vy = obj:getLinearVelocity() if( correctedX ) then vx = 0 end if( correctedY ) then vy = 0 end if( correctedX or correctedY ) then obj:setLinearVelocity( vx, vy ) end end local physics = require "physics" physics.start() local boy = display.newImageRect( "images/boy.png", 80, 90 ) boy.x = display.contentCenterX boy.y = display.contentCenterY + 300 physics.addBody( boy, "dynamic" ) function boy.enterFrame( self ) stayOnScreen( self ) end Runtime:addEventListener( "enterFrame", boy ) function boy.touch( self, event ) if( event.phase == "ended") then self:applyLinearImpulse( 0, -10 \* self.mass, self.x, self.y ) end return true end Runtime:addEventListener( "touch", boy )
#30

Note: This will be my last answer for the day.  I’ve gotta get back to work.

#31

Ok, thanks, me too. I need to sleep so this post is my last post. :slight_smile: Thanks by the way. :slight_smile: