- Getting to Know Our Tools 4:52
- Android Tools Overview 5 questions
- Editing a Layout File 4:52
- Changing Text in a Layout 1 objective
- Adding a TextView 4:15
- Changing Text Size 1 objective
- Adding a Button 4:31
- Adding a Button 1 objective
- Setting Colors 5:26
- Setting Colors 2 objectives
- Setting Padding 1:13
- Setting a Fullscreen Theme 3:30
- Setting Padding 1 objective
Preview
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Adding a Button
4:31Continuing with Views and Widgets, let's see how to add a Button to our layout!
All right, now it's my turn.
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I'm going to grab a button from over here
in the palette under the widgets category,
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and then drag it to
the bottom of the screen.
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And it looks like I'm getting that same
mismatch between the orange box and
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my button so I'm just going to
place it and then re-pick it up.
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Now I'm looking for
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a solid green line along the bottom to
show that I'm aligned to the bottom edge.
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And a vertical dotted
line going up the center
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to show that I'm centered horizontally.
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Once I see both of these,
I'll drop the button in place.
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Looks good, but we should probably change
the word "button" to something else.
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Just like a text view,
buttons also have a text property.
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Let's change this text to say,
show another fun fact.
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Hit Enter and there is the text.
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Now we'd like our button to stretch to
take up the whole width of the screen.
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We can do this by simply
clicking on this button up here.
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This toggles a property of
the button called LayoutWidth.
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If we look at the top of the properties
pane we can see the value change.
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It's currently set to match_parent, which
matches the size of its button to its
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parent, which in this case is the whole
screen, but if I press the button again.
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It changes to wrap content, which wraps
the content of the button It makes it as
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small as possible based on
the content that's inside.
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Let's flip that back to match parent.
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Cool, this may not be very pretty yet,
but this is the basic structure for
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our screen.
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Let's do one more thing before we make
the button actually do something.
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Let's switch to the XML view,
by clicking on the text tab at the bottom.
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Notice how we have XML elements
called TextView here and
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here that represent our two text views.
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Then down here we have a new button XML
element that represents our button.
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When we drag and drop a view onto
the screen from the design tab
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this is the kind of XML that gets
produced to represent that view.
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If we wanted to, we could have typed
this all out instead of dragging and
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dropping to the screen.
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Let's take a look at the second text view,
the one with the fun fact.
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It has a property called ID,
which is set to @+id/textView.
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This part after the slash,
is the actual id textView.
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We can also see that an ID
was generated for a button.
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@+id/button, the @+id/ part
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is the prefix that let's Android know that
this is an id we can use in the system.
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The id itself is also important because
it's what we'll use to refer to these
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views from within our code.
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These generic ids will work, but
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we should really strive to name
things more descriptively.
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It will help us make more sense of
our code when we revisit it later.
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We can just change them in here.
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But if we do, we'll also need to update
every reference to these ids in our code.
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Now, there aren't yet
any other references to these IDs.
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But it could be big deal
in a more complex project.
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For that reason,
it's a good practice to change IDs and
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most other things by doing a refactoring.
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Refactoring is awesome, because we
can rename our ID in one place and
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Android Studio will take care of updating
every reference to that ID automatically.
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Let's right click on the ID for
our fun fact text view and
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then select Refactor and then Rename.
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Then let's change the ID from
textView to facttextView.
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Be sure to leave the @+id/prefix and
then hit Enter to rename it.
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Let's also change the ID of our button.
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Right click on its ID,
select refactor, then rename,
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and let's name it showFactButton
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then hit Enter again, and
we're back to the XML view.
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Awesome, let's run our project to
make sure that everything looks
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okay in the emulator.
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And this time let's check the Use same
selection for future launches check box so
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we aren't presented with this dialog
each time we want to run our app.
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Then hit OK to run it.
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All right, we're looking good.
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Okay, so it doesn't do much but
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we can tap on our button down
here to our heart's content.
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