- Accessing Views in Code: Declaring Variables 5:20
- Accessing Views in Code: Assigning Variables 6:24
- Initializing a Button 1 objective
- Making a Button Do Something 4:35
- Adding the OnClick Method 2:36
- Android Programming Basics 5 questions
- Generating a Random Number 4:08
- Choosing a Random Fact 4:52
- Using the Random Class 4 objectives
Preview
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Adding the OnClick Method
2:36The OnClick method is called when the button is actually clicked (or tapped). Any code in the OnClick method will run each time we tap the button!
We just left off with a lot of code
that was generated by auto complete.
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We use on click listeners
like this a lot in Android.
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So it'll make more and
more sense the more you use it.
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This on click method,
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will run when ever this listener
detects a click on our button.
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Just like opening our app
triggers the onCreate method,
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typing on our button will
trigger this onClick method.
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So anytime we click on our button,
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the code that we write inside
these curly brackets will run.
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Let's add a comment in the onClick
method to describe what we'd like to do.
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The button was clicked,
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so update the fact
TextView with a new fact.
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All right, now we need a new fact.
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On the line below our comment, let's
create a new string variable named fact.
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And let's set it equal to in
quotation marks Ostriches
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can run faster than horses.
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And don't forget the semicolon.
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Now we need to update our text
view to show this new fact.
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Remember when we were editing the layout?
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We can change the text of a text view
by editing it's text property or
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by changing it directly
in the layout's XML file.
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Android also allows us to make
these kinds of changes in code.
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On a new line type factTextView.setText
and then hit Enter to autocomplete.
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Notice that there's a list of
different parameters down here.
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This is because there are different
versions of this set text method.
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Each taken different parameters.
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We want this first one because it
only has one parameter for the text.
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Now the data type here, CharSequence,
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might be a little confusing
since we're using a String.
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But a String is just
a sequence of characters, so
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it shouldn't be too surprising that
all Strings are also CharSequences.
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Kind of like how text views are also
views or how dogs are also animals.
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In Android,
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whenever you see a Charsequence,
you can just pass in a string.
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All right, let's type fact in between the
parenthesis to pass in our fact variable
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and now we are ready for
the moment of truth.
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Let's click on the Run button,
or hit Ctrl + Alt on Mac,
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or Shift + F10 on Windows to run our app.
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Looks good.
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Let's click on the button to test it.
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Did you know that ostriches
can run faster than horses?
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