Corona – Groups

At some point you will want to work with groups of display objects. Corona provides a special type of Group display object.

Try out groups for yourself. Start by making a new Corona project.

1. Create a folder to work in
2. Create a new text file, save it to your folder named main.lua
3. Add a few small images to your folder

First create three images.

local square = display.newImage("square.png")
local circle = display.newImage("circle.png")
local hexagon = display.newImage("hexagon.png")

 

Next create a group.

local group = display.newGroup()

Now add the objects to group

group:insert( square )
group:insert( circle )
group:insert( hexagon )

 

Now we’ll off set the images a little. Here placed circle near the upper right corner of square and hexagon near the lower left corner of square.

square.x = 0
square.y = 0

circle.x = 50
circle.y = -50

hexagon.x = -50
hexagon.y = 50

Now try transforming the group. Notice all of the images transform as a group. Placing the group in the center of the screen moves all of the images there. Rotating the group rotates all of the images. All of the transformations are based on the group’s reference point.

group.x = 160
group.y = 240
group.rotation = 5
group.alpha = .5

You can also animate the group. Try the following.

transition.to( group, {time=3000, rotation=360, transition=easing.inOutExpo})

A group acts as a display object in every way, with the difference that Groups can contain other display objects including other groups.