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(upbeat music)

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(swoop)

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(typing)

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In this section we're going to create

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a basic calculator, as you can see on the screen,

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and that's gonna give us a chance to practise

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what we've learned about layouts

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with a more complex example and we'll also be

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connecting code to a lot more buttons

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than in our previous button click app.

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In this section, we're gonna look at

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working with groups of widgets to see how we can do things

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like constraining them to be positioned as a group,

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as well as setting common properties

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for multiple widgets at the same time.

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And we'll also show a slightly different approach

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to creating on OnClickListener,

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so that the same method can be used by multiple buttons.

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Now this app as you can see is a basic calculator

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and it will let you enter numbers using the app's buttons,

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then perform the calculation when any of the

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operation keys are pressed.

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The plus, minus, multiply and divide.

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Now the stock Android calculator builds up the

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calculation on the screen, and doesn't actually

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evaluate it until you press the equals sign.

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But ours is going to evaluate each sum

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as soon as you press the next operator,

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just like early calculators did.

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And we'll have two lines for display

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so you can see though,

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so you will be able to see both numbers at once

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and won't have to remember the previous one,

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like you did with those early calculators.

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And also, unlike the early calculators, it'll show you

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which operation it will perform next,

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so you don't lose track.

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Pressing equals will update the display with the result.

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It can also be used to start a new calculation

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by transferring the entered number up into the result,

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ready to use in the next calculation.

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First let's have a quick demonstration here

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of this calculator app to see how it actually works.

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So I can enter a number like by clicking on it,

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nine

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and multiply three equals 27.

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Then I can also continue with that

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by putting 10

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multiplied

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and you can see the value's getting updated there,

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and we can clear it by just pressing equals,

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and I can type in something like 20

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plus

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to add 20 to it so I've got the value of 290.

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And the other thing that we're gonna be doing

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in this section of the course is working with

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both portrait and landscape versions.

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So if I'm going to serve it to landscape now,

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and you can see we've got a slightly different result there.

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We've got the layout looking a little bit different

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to take advantage of landscape mode.

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So we'll be learning how to do that as well.

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I'll just move that back to portrait.

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And then also I've got the value that we've been using

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stayed there when we moved from landscape

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back to portrait, and then from portrait to landscape.

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And we'll also be showing you how to do that

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in this section of the course as well.

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And later in this section, we're going to have a look

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at guidelines, which can be used in a constraint layout

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to a link which is either vertically or horizontally

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so that you can anchor widgets to them.

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Right, so let's move back now to Android Studio

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and we can start work on this project.

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So let's get started now creating a new project

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and then in the next video we're gonna look

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at the actual layout of our calculator.

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So start Android Studio and we're gonna click on

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start a new Android Studio project.

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Now I'm gonna call this calculator,

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(typing)

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I'm going to leave the company domain name the same,

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learnprogramming.academy.

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Now Android Studio's suggesting a suitable location,

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project location, ending with a care calendar directory

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and you can store the project somewhere else if you want.

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But Android Studio normally remembers where you've told it

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to create projects so only the

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fallout directory name changes.

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So I'm gonna leave it as the default onscreen there,

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and there's another important option we have to select

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on the screen, and that's this option down here to

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include Kotlin support.

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Now remember to tick that box if you wanna generate

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Kotlin code and make sure it's unticked

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if you want Java code.

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In my case, I'm going to leave it ticked

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and click on next

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and we're gonna continue to use the minimum

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STK of 17 and you can see this API 17

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is already selected here.

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So you wanna make sure that that is checked

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and leave everything else unchecked

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and then click on next again.

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Now we're not going to have a menu in this application,

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so empty activity which is selected here

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for me automatically is our best choice

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for the template to use,

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so make sure you select that

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and click on next again.

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And once again we're just going to accept the names

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that Android Studio has suggested for both the

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activity name and the layout name,

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and just make sure that both the generate layout file

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and backwards compatibility AppCompact check boxes

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are checked and then click on finish.

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So that's the project created,

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I'm gonna leave it just building

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and in the next video we'll actually start producing

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the layout for our calculator app.

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So I'll see you in the next video.