Gadgetory

hello everybody my name is Gary Sims from Android authority now there are many reasons to want to write an Android app maybe you've got a great idea when you want to approach type it on Android maybe you know about PC programming you want to move over to mobile maybe it's part of a college or university course whatever the reason is writing Android apps can be fun and rewarding and today I'm going to show you how to write your first Android app okay before we begin we need to mention a couple of things first of all you really need to know a little bit about the Java programming language to get you through this particular tutorial now I've already done a video on Java basics you can find that video on the Android - YouTube channel you can also find the accompanying article on the Android or thority website I do recommend that you go and read that now when I made that tutorial some people left in their comments that they thought I was going too fast through the material so for this video I'm going to say two things first of all I'm going to repeat certain elements a couple of times just to make sure that you've got them when they're particularly important and secondly please do use the pause button and go back and watch things again if you didn't quite get it on the first time around okay so let's start okay so to write an app you're going to need a downloading installed Android studio that's provided by Google and if you can't find it you'll find the link to it in the written companion to this video on the Android authority website now included in the download is the software development kit for Android that all the bits and pieces you need to develop an app as well as the Android emulator so that you can initially test your app on a PC without needing to install it on a real device however before you install Android studio you're going to need to install the Java development kit from Oracle go over to the written companion and you'll find the links to tell you where to download the JDK now you need to make sure you download the right version I have a 32-bit or 64-bit check which version of Windows are running and download the right one because if you don't you're going to have trouble running Android studio install that and then you can install Android studio during the install you'll need to configure how much memory to reserve for the Android emulator now the emulator runs Android in a kind of virtual machine as an Android phone with an Intel processor this is faster than emulating an ARM processor on your PC however to do this the virtual machine needs to allocate some memory the installation program will recommend how much memory to reserve and it's probably best to accept the default however be aware that the combination of Android studio Java and the emulator all running together can be quite memory hungry and your PC will slow to a crawl unless you have lots of RAM google says you need two gigabytes of RAM as a minimum and that four gigabytes of RAM is recommended however my main PC has 8 gigabytes of RAM and sometimes it still struggles when you first run Android studio it will perform some initialization including downloading installing the latest Android SDK this can take several minutes so you will need to be a bit patient when it finally does all start up you'll be presented with a nice menu that allows you to start a new project open existing project import a project and so on and as you might expect you to click on start a new Android studio project you will then need to enter in a name for your app in the application name field I will suggest something like my first app and in the company domain field you need to enter the domain name of your company if you're an independent developer or hobbyist enter your own domain name if you're just experimenting with Android and won't be publishing your apps to Google Play anytime soon then just leave the domain as it is maybe you could just change the word user to your own name on the next dialog make sure the phone and tablet is selected and that the minimum SDK is set to API 15 Android 4.0.3 make sure that where and TV are not ticked on the add an activity to mobile dialog use the default blank activity and then click Next again on the customize the activity dialog just use the default values and click finish the integrated development environment IDE will now start this can take several minutes especially if it's the first we've created a project when the IDE appears if you see the error message rendering problems rendering failed with a known bug then just click the rebuild link as indicated next to the error the default workspace for the IDE is split into three parts excluding the toolbars on the upper left is a project tree to its right is the code editor and designer and beneath them both is where you'll see the various messages from the compiler and so on at this point you can actually compile and run the auto generated code however it's not very interesting so what we're going to do is we're going to add a few things not very much but just enough to give you a taste of Android app development the project tree holds the different files and resources that you need to build your Android app under the app node in the project tree you will see several other nodes like folders subfolders which you can expand the top-level nodes are manifests Java and res and res stands for resources under manifests you'll find the file Android manifest or XML every application must have one of these files it's an XML file with information about the app including its name one of the most common things that you'll add to this file is the list of permissions needed by your app for this simple test we won't need to change anything here under the Java folder you'll find the Java code for your app in fact you'll find it under a subfolder some called something like condor example dot user dot my first app or whatever is the domain name that you entered earlier on when we started the project under that folder you'll find a file called main activity Java this is the entry point for your app and for our example app this is the only Java file we're going to need but we are going to need to add some Java into this file so just again so you got that the under the Java folder you're going to find a subfolder with a domain name of your company with the app name appended to it and under that you're going to find mainactivity.java and that's the main entry point very simple out under the resources folder the res folder you're going to find lots of other subfolders now this is where the different resources for the project are kept that means graphics string values menus and most importantly where the definition for the user interface is stored now the two that are of interest to us for this example app are layout and values under layout you'll find a file called activity underbar main.xml it is an XML file that describes the user interface there are two ways to edit this file the first is to edit the XML code directly and the second is to use the built-in UI designer so under res layout you'll find a file called activity main.xml and this is the file that describes the user interface for your Android app now once you become proficient and an expert Android app development you may find yourself often editing the XML file directly but thankfully Android studio has a built-in UI designer and as you change elements on the UI using the designer it automatically creates the corresponding XML file and that's what we're going to do in our sample app in a few moments the values folder contains several different XML files and the most important one for this example app is strings dot XML rather than hard coding string valued into the Java code values are placed into strings dot XML and then they are referenced using an ID now the advantage of this system if a string needs to be changed in multiple places all you have to do is change it once in strings dot XML and it will be changed throughout all of the code it also makes supporting multiple languages in the app that whole much easier so just to repeat that strings dot XML is where the string values are stored and in the Java code and in the XML file for the layout you just reference the string using the ID and we'll see about that in a few minutes so just to sum up then to create this sample app that we're going to do today you need to modify mainactivity.java to add some Java code we're going to need to modify activity underbar main dot xml because we're going to change the UI and we're going to need to modify strings or xml because we want to add some hard-coded strings like ok or tap me into that file so let's start by altering the text of the label and changing its alignment first find the activity underbar main dot xml file in the project tree and double click remember the activity main.xml is the file which holds the user interface definition at the bottom of the code window there are two tabs design and text make sure you are using the design tab now click on the text hello world that is shown on the rendering of the phone if it's too small user zoom buttons the plus sign the magnifying glass to enlarge the rendering of the phone in the property windows just to the right of the phone image scroll down until you find layout : Center in parent click the space next to it and select horizontal the hello world text will now jump to the horizontal Center now to change the text the string hello world is held in that file we mentioned earlier strings dot XML under resources values if you double click on the file you'll see a few lines of XML that define a few strings used by the app find the still line that says string equal to hello world in angle brackets then hello world and then the closing string tab and change the hello world exclamation point to tap me if you dare now to add the button back on the design tab of activity underbar main door XML fine and click on the button in the pallet list on the left hand side of the phone rendering now click somewhere beneath the text tap me if you dare on the phone image so it's somewhere in the middle now double-click on the button so that you can change the text the quick and dirty way is just to change the text and leave it hard-coded in the Java file however since we've already been used to using strings dot XML it's best that we carry on using it at the end of the text field is a button with three dots click on it in the resources window that appears click on new resource and then new string value in the resource name enter tap me and in the resource value enter tap me exclamation point now click OK and you'll notice that the button now says tap me the final step is to add some Java code which reacts to the button being tapped one of the UI elements of Android is called a toast a toast provides simple feedback in a small pop-up that appears for a few moments and then disappears you've definitely seen it when you've been using Android for example in Gmail navigating away from an email before you send it triggers a message saved as a draft toast toast appear automatically and then disappear after a predefined timeout for our sample app we will need to display a toast every time the button is tapped the first step is to add some Java code find mainactivity.java and add the following code beneath on create the word view as in view v will likely be in red with a message bubble displayed near it this is Android studio telling you have used a new construct view without importing it in the import section of the top of the Java code this is actually very easy to fix click on the word view and press alt enter Android studio will fix it for you if the word toast is in red then do exactly the same thing click on the word toast and then press alt enter now back in the designer for activity under bar main door XML click on the button and scroll down through the property list until you find on click click on the combo box to the right of it and it will see a list of functions click on on button tap that's the function we just added to the Java code so now the on button tap function will be called whenever the button is tapped when it is called it creates a toast called my toast that will display the message ouch to show the toast we just call my toast dot show and that's it in terms of writing the app now it's time to test it in the emulator under the Tools menu navigate to Android AVD manager this tool shows you the current list of configured Android virtual devices you will have one device configured by default probably a nexus 5 click on the play icon the triangle under the actions column and this will start the emulator now depending on the performance of your PC and how much RAM you have the emulator can take several minutes to start up once the emulator is up and running go to tools and click run app this will compile your app and send it to the emulator during this process Android studio will ask you which emulator to use you will see your emulator in the list it should be the default option so just click OK the app will appear in the emulator eventually you can now click the tap me button and watch for the toast to appear towards the bottom of the emulated device congratulations it's actually possible to run your app on a real Android device and the easiest way to do that is to enable USB debugging on your phone and connect it to your PC the USB debugging option can be found under settings developers if you don't have a developers option in your settings menu then go to settings about and tap the build number 7 times with the device connected click on run out under the Tools menu but this time don't send the app to a virtual device send it to a real device if your device isn't listed either means that you haven't enabled USB debugging or you need to install the appropriate USB development drivers for your device Google has some documentation on this and you'll find links to it in the written companion well obviously this is just the beginning but you have today written yourself your first Android app with a little bit of user interaction and what you should now do is write your second app and then your third app keep adding to it keep learning Google has lots of lots of training material there's lots of documentation there's lots of sample code but the thing to remember is just keep having fun keep experimenting and keep having fun you'll find it very rewarding now do keep coming back to and royal throaty calm because we're going to keep posting developer related content for you new tutorials new things in the future so do keep tuning in you should probably also sign up to the android authority weekly developer newsletter you'll find that dev weekly Android or thority com if you enjoyed the video please give it a thumbs up also don't forget to subscribe to our Android Authority youtube channel if you've got any questions please use the comments below and we'll see if we can help you if you had any problems developing this first app and as for me I'll see you in my next video