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Well done!
You have completed Build a Simple Android App with Kotlin!
Preview
Let's continue with adding additional colors as the background for each new fun fact. We'll add a new Java object to hold the colors and serve one up on each tap of the button!
Color codes (from the style guide)
val colors = arrayOf(
"#39add1", // light blue
"#3079ab", // dark blue
"#c25975", // mauve
"#e15258", // red
"#f9845b", // orange
"#838cc7", // lavender
"#7d669e", // purple
"#53bbb4", // aqua
"#51b46d", // green
"#e0ab18", // mustard
"#637a91", // dark gray
"#f092b0", // pink
"#b7c0c7" // light gray
)
Documentation
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It's finally time to
add colors to our app.
0:00
Let's create a new class called
ColorWheel, that stores our colors and
0:03
picks new ones for us.
0:07
It'll be very similar
to our FactBook class.
0:08
In the project name,
let's right-click on the package name and
0:12
select New > Kotlin File/Class.
0:16
Let's name it ColorWheel.
0:19
Make it a class instead of a file,
and hit Enter.
0:22
Now we're going to copy and
past our code from our FactBook class and
0:26
make a few key changes.
0:29
Let's switch over to our FactBook class.
0:32
Then let's select
everything after the word,
0:35
FactBook then use Cmd,
or Ctrl+C to copy it.
0:38
Then let's go back to
the ColorWheel class,
0:41
select everything after
the word ColorWheel.
0:44
Then use Cmd, or
Ctrl+V to paste it back in.
0:47
Android Studio then notices
that we're missing an import.
0:52
We didn't copy the import
statement form our FactBook class,
0:55
which means it didn't get pasted here.
0:57
Hit OK to generate the import,
and now we're good to go.
1:00
Instead of facts,
we'd like these to be colors.
1:04
Let's start by refactoring
facts to be named colors.
1:07
Right click on facts,
select Refactor > Rename.
1:11
Note that the keyboard
shortcut is Shift+F6, and
1:16
then type colors and hit Enter.
1:20
Now I'm going to copy and paste in some
colors in the form of hexadecimal strings.
1:24
Remember, the colors we want to use are
the Treehouse topic colors from the web.
1:30
Here's the color sheet
we looked at before.
1:35
There's a link in
the teacher's notes below.
1:37
If you want, you can come to this page and
individually grab each code and
1:39
create the array.
1:43
But I'll copy and paste in the array
from the teachers notes to save time.
1:44
Okay, let's copy the array and
then back in Android Studio,
1:48
I'm going to put this last closing
parenthesis on a new line.
1:52
And then paste our colors
array over our facts array.
1:55
Now, that we've got all our colors, let's
make a few changes to the getFact method.
1:59
First off, we probably shouldn't
call it getFact anymore.
2:04
Let's change it to getColor.
2:08
Since this method is never used,
that's what this gray text is telling us,
2:10
we don't need to bother with refactoring.
2:14
We can just rename it
the old-fashioned way.
2:16
Great!
2:20
Now the cool thing is we don't need to
change anything about our randomNumber
2:21
generator.
2:25
We still use the random class and
2:26
still pick a random number based on
the length of the array up here.
2:27
Though we should change the comment
to say Randomly select a color.
2:32
Now let's get back to FunFactsActivity.
2:37
And the first thing we need to do is
create a new ColorWheel object as
2:40
a property,
just like we did with FaceBook.
2:44
Let's add a new line at the top below our
FactBook and create a new private vowel
2:47
named colorWheel.
2:51
And set it equal to a new ColorWheel.
2:56
Now down in our on click listener,
3:00
we can pick a new color just
like we did for the fact.
3:02
Let's add a couple lines
after we set our fact and
3:06
then type val color =
colorWheel.getColor().
3:12
Then let's use our new color
variable as a parameter to
3:18
this setBackgroundColor method.
3:21
Which gives us an error.
3:24
If we hover over it, we'll see
the we're getting a type mismatch.
3:27
The method expects an int,
but we're giving it a string.
3:31
So how are we gonna make this work?
3:34
Well, don't worry,
as usual there is this simple solution.
3:37
We need to convert data like
this a lot in programming.
3:40
Remember programming is primarily about
working with and manipulating data.
3:43
Let's take a short break, and then in
the next video, we'll fix this error.
3:48
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