- Simple Refactoring: Creating a New Class 5:45
- Creating a New Class 2 objectives
- Simple Refactoring: Using a New Class 3:47
- Simple Refactoring 5 questions
- Dynamically Changing the Background Color 3:58
- Dynamically Changing the Background Color 1 objective
- Adding More Colors 3:52
- Using the New Colors 3:38
- Adding Colors 1 objective
- Adding an App Icon 4:47
- Adding an App Icon 3 questions
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Dynamically Changing the Background Color
3:58The last thing we need to do is pick a new background color each time we display a new fact. Try it yourself, then watch this video for my explanation.
We're almost done.
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The last thing we need to do
is pick a new background color
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each time we display a new fact.
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Sounds simple enough, right?
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If you're feeling adventurous, why
don't you pause me and try it yourself.
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Then come back and see how I do it.
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Here are the steps you need to do.
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Step one, declare a property with
the data type of RelativeLayout?
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And set it equal to null.
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The format is just like
our other view fields but
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with a different name and data type.
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Step two, set this property in the
onCreate method just like the other views.
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You may need to add an ID to
the RelativeLayout in the layout file.
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Step three, where we set a new fun fact,
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call the setBackgroundColor
method on this new variable.
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Use Color.RED as the parameter.
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All right, did you get it working?
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Let's switch to FunFactsActivity and
start from the top.
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Declare a property with the data
type of RelativeLayout?
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Let's add a new line below our
showFactButton declaration,
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and type private
var_relativeLayout: RelativeLayout?
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And set it equal to null.
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Okay, on to step two.
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Set this property on the onCreate method.
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Let's add a new line below where
we initialized showFactButton.
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And then type relativeLayout
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= findViewById(R.id.).
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And that's right, we haven't give
our relativeLayout and ID yet.
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If we had, we will be be able
to see that ID in this list.
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Let's open of our layout file.
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So Project > res > layout
> activity_fun_facts.xml.
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Let me have the preview and
inside this first RelativeLayout tab,
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let's add an ID property.
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Let's add a line after where
we set the padding and
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type android:id="@+id/relative
" with a lower case r.
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Remember, we could have also set
the ID from the design tab by
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selecting the RelativeLayout
from the component tree and
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then setting the ID on the property pane.
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Looks good, let's go back to our
activity and reference our new ID.
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Let's hit Ctrl+Space,
to bring back up auto complete.
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And then select relativeLayout.
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And finally,
add the cast to relativeLayout.
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So much for step two.
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Next step, step three,
where we set a new fun fact called the set
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background color method on our new
variable using Color.RED as the parameter.
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This is referring to our onClick listener.
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At the bottom,
let's reference our new variable and
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assert that it isn't null,
relativeLayout!!
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Then, using auto complete as our guide,
let's add a dot and type sbc.
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Just typing the first
letter of each word and
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a method is another way to let auto
complete know what we're looking for.
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Let's select
the setBackgroundColor method and
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it takes in an into
color as the parameter.
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For this example,
we're just using a system color.
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Inside the parenthesis, let's type
the class name, Color with a capital C.
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And hit Enter to import it and
then add dot RED.
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All right, let's give it a shot.
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Now, when we first tap the button,
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it should change the background
color to red and it does, cool.
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Let's pause for a moment and
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then we'll make some changes to
use a new color for each fact.
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