Sprite position in Corona SDK

I didn't understand some object position concepts in Corona SDK

I have created sprite sheet:

local spriteSheet = sprite.newSpriteSheet("button.png", 138, 64);
local spriteSet = sprite.newSpriteSet(spriteSheet, 1, 2);
local sp = sprite.newSprite( spriteSet );

and it's positions are strange and sprite is开发者_StackOverflow out of screen bounds even I set x and y positions to zero

config.lua is:

application =
{
    content =
    {
        width = 320,
        height = 480,
        scale = "letterbox"
    },
}

I think that problem in "referencePoint"

just say me how to change setReferencePoint of default screen (not image or group ...), just default screen...

Technically you can use a different coordinate system for all your graphics by creating a display group and attach everything to that group, but really it seems like you're asking the wrong question. Rather than trying to change the reference point of the screen, you should be wondering why your sprites aren't positioned correctly.

Please create a new question that focuses on that problem and explains it further, because all you say here is that the positions are "strange". What's that mean?

You can modify your code like below and just check it,it will work:

local spriteSheet = sprite.newSpriteSheetFromData( "button.png",require("button").getSpriteSheetData())
local spriteSet = sprite.newSpriteSet(spriteSheet,1,9);
sprite.add(spriteset,"button",1,9,1000,0);
//button is lua file use button.lua
local sp = sprite.newSprite( spriteSet );
sp:prepare("button");
sp.x = display.screenOriginX+138;
sp.y =  display.screenOriginY+64;