This is meant to be a simple talk for people who've done front end dev to get used to the similarities and differences of writing android applications. It is the first in a series, if you have any improvements or ideas please feel free to make an issue or reach out to me. Thanks!
Make sure you have git installed. If you don't, here you go.
sudo apt-get install git
OR
brew install git
Use the Github desktop app to clone this repository or go to your command line, create an android folder on the Desktop, and we'll clone our example app.
mkdir android
git clone https://github.com/DavidAwad/SimpleAndroidYou now have all the source code you need! Just import the project into Android Studio.
So the point of this app is to do some Basic I/O in Android on the latest SDK.
We'll take some form input, render the input on the screen and change it's colors. The colors can be changed through two buttons on the screen, in addition we'll create a button that will jump to a completely separate activity.
Most of the hierarchy of Android happens through activities. You can think of activities as a sort of "execution context" for an android application. More simply put, an activity is what screen of the application the user can currently see.
Since this is the case, each activity has some code that determines how the screen will appear and has code that handles what the app can do. Kind of like HTML and JavaScript. Where each html page has Javascript that is specified for it and there are links on each HTML page that define what other pages you can go to.
So for example let's look at the MainActivity.xml file and MainActivityCompleted.java files. These can be found in the src directory. Java determines our functionality and the xml determines the appearance between the two. The way that the java file interfaces with the resources and buttons in the screen layout is through the resource collection referred to as R.java.
You'll see that we create pointers through references to the unique ID's on every single resource, which are defined inside the XML. After that you can manipulate these pointers with event listeners and whatever other functions the android library provides.
Still Confused? Just take a look at the code. There are a lot of comments that will guide you straight along!
Enjoy the Docs! --David Awad
You'll notice that the icons have been changed. You can start your new project by opening up Android Asset Studio and designing a cool simple logo for your new project. You can import the generated icons by simply moving the files into the corresponding folders inside of app/src/main/res/. In there you'll see the different drawable folders for different screen resolutions.
Since you're a hotshot designer now why not try using Material Design? Here are some Material Design Examples for you to mess with.
After that you can try adding some api calls or http requests based on user input and displaying the output on the screen. Now that you can style things out.
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You may get an error talking about there being a required
content.Contexttry looking at this -
If you get something about being unable to resolve R.java, try going to gradle > clean project. Or Gradle > rebuild project.
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You may get an error looking something like
X:XX:XX PM IllegalStateException: Cannot locate factory for objects of type DefaultGradleConnector, as ConnectorServiceRegistry has been closed.: Cannot locate factory for objects of type DefaultGradleConnector, as ConnectorServiceRegistry has been closed.
If you get this error try re-starting android studio.
##Resources ####Awesome Android is a huge index of useful libraries and packages to do things on Android. ####Android-lite-http is an easy way to make http requests on Android. ####Material Design Examples and Widgets ####Material icons ####Android Assets Generator by the great Roman Nurik
This code was originally written by Shreyas Hirday with some edits by me. He's a developer with mySwapp LLC, feel free to connect with him.