- Simple Refactoring: Creating a New Class 5:54
- Creating a New Class 2 objectives
- Simple Refactoring: Using a New Class 6:28
- Simple Refactoring 5 questions
- Dynamically Changing the Background Color 3:51
- Dynamically Changing the Background Color 1 objective
- Adding More Colors 3:43
- Using the New Colors 3:42
- Adding Colors 1 objective
- Adding an App Icon 4:50
- Adding an App Icon 3 questions
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Dynamically Changing the Background Color
3:51The 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 fun 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 1, declare a field or member variable
with a data type of relative layout.
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The format is just like our other View
fields, but with a different name and
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data type.
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Step 2, Set this field 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 3, 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 fun facts activity and
start from the top.
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Declare a field with the data
type of RelativeLayout.
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Let's add a new line below our
showFactButton declaration and
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type private RelativeLayout and
let's name it RelativeLayout.
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Okay, on to step two.
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Set this field and 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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then a cast to a relativeLayout,
followed by findViewById.
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And then in parenthesis, type R.ID.
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And that's right, we haven't given
our relative layout an ID yet.
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If we had,
we'd be able to see that ID in this list.
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Let's open our layout file, so
open the project pane, Res Directory,
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layout Activity fun facts and
then I'll close this directory again.
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And inside this first relative layout tag,
let's add an ID property.
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Let's add a line after padding and
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type android:id= and
then in quotation marks,
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"@+id/relativeLayout with a lowercase r.
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Remember, we could have also
set the id from the design tab
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by selecting the relativeLayout
from the component tree and
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then setting the id in the property pane.
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Looks good.
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Let's go back to our activity and
reference our new id.
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Let's hit Ctrl+Space to
bring autocomplete back up.
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And then select Relative Layout.
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And add a semicolon.
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So much for step two.
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Next up, step three, where we set
a new fun fact called the setback
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onColor method on our new variable
using color.red as the parameter.
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This is referring to the onClick method.
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At the bottom, let's add a reference
to our new variable, RelativeLayout,
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and then using auto complete as our
guide let's add a dot and type sbc.
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That's right, just typing the first
letter of each word in a method
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is another way to let auto complete
know what we're looking for.
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So let's select
the setBackgroundColor method, and
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it takes an int color as a parameter.
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For this example,
we're just using a system color.
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Inside the parentheses,
let's type the class name,
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color with a capital C,
and then add .capital RED.
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All right, let's give it a shot.
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Now when we first tap the button, it
should change the background color to red.
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And it does, cool.
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Let's pause for a moment and then we will
make some changes to use a new color for
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each fact.
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