#Introduction Welcome to Hello Developer, a simple app to help get you antiquated to the awesome world of Android Development. While we won't do any crazy - at least not yet - it's a great way to get started fast, and we can build on this later.

A couple comments to keep in mind as you explore this project:

• In case you are looking at this project because you missed the workshop, look at this quick video that tours the project structure of an Android app. This should help remove any intimidation you might feel when you first open up Android Studio

• Most of these ideas generalize to other platforms you may find yourself writing apps for; if you learn Android dev, its not too different from writing iOS apps!

• I encourage you to Research and Experiment with anything that seems confusing.

• I'm always open to suggestions, questions, and comments concerning this app and Android development in general. One can contact me via email: kcampos0101[AT]gmail.com.

#Saying Hello Traditionally, the first program any programmer writes is the Hello World program. The goal is to simply print out "Hello, World!" We'll make it a bit more interesting by having the user type in their name, tap a button, and we will deliver a nice, customized "Hello World!" message. Check out activity_mail.xml in the file pane on the left, which will show you what the app will look like when we run it.

#Quick Tour Let's have a brief overview of the files contained in this project. I encourage you to Google these topics and look at Google's documentation to further your understanding:

###app In here we will find all the files relevant to the development of our app.

###Gradle Scripts Here we will find all files relevant to Gradle. Gradle is Android's build tool of choice. Its okay if you don't know what a build tool is - We won't be touching gradle files for this project.

###app/manifests Here you will find AndroidManifest.xml. This file tells the operating system the details about your app. Some examples include any required permissions, your app's name, and the icon to use.

###app/java Here is where you will write your app's logic. You will find three directories that roughly fit the path of com.example.com.myapplication. Two of them will be labeled androidTest and test in parenthesis. The main folder without tags is where we will be writing our code. The other two folders are for writing test scripts to make sure our code is well built. In test, we want to write test cases for all things that do not require us to use any Android classes. androidTest, in contrast, is for test cases that require Android classes. The reasoning for this seperation is because any tests involving Android classes will require you to load an android emulator. This results in much long testing times. The seperation allows us to run our non-android tests without the delay of an emulator.

###app/res Here is where all the content (resources) of our app lives. There are various directories here that are used for resources such text, images, audio, and coloring for your app's theme is specified. The one you will use most frequently is res/values/strings.xml. This file holds all static text that appears in your app. Having all of our text in one file allows us to easily translate our app. The operating system will load the correct set of strings based on the system language. Its this type of structure that allows android apps to be very device-flexible.

###app/res/layout/activity_main.xml Here is where we will create the UI for our app.

On the left, Android Studio renders a representation of what the app will looking like at runtime. On the right, Android Studio renders outlines of what components you have placed on the screen.

This left-hand-side can be very useful. Minimalist styling trends can make it difficult to distinguish where one UI element begins and another ends.

Left of these renderings, you'l find a panel labeled Palette. In here, you can drag UI elements over onto the rendering and place them as you see fit. Go ahead and drag an EditText object onto the rendering. Note: It is important that you grab an EditText and not a TextView. EditText objects allow you to input text while TextViews simply display some text. If you choose the wrong object, your app will not work. Click on the EditText object and on the left you will see a Properties panel.

Go ahead and change the hint field to say "Please enter your name". Now, remove whatever value is in the text field. A hint is that grayed-out text you see in a form that lets you know what a field is expecting.

Second, drag a button onto the screen. Click on the button in the rendering. In the Properties panel, go down to onClick and type greet. We have now specified what function will be called when the button is pressed.

Okay, now we're done laying out our UI. Easy, right? Now lets move on to adding some functionality

###app/java/com.example.www.myapplication/MainActivity.java Here we will be writing the logic that handles our UI componenets.

Go ahead and create a new public method that takes in a View as its only parameter. We will call this method from the front end to greet our new android developer.

Your method should take the signature: public void greet(View vew). This is because this is what we specified in the button's onClick field. Now we move on to writing the inside of this function.

Inside, we will ask for the EditText object on the front end that the user will put their name into. This is done with the following line: EditText nameField = (EditText) findViewById(R.id.editText);. Now, from this object we will grab the text that it is holding. On a new line, we type: String message = nameField.getText().toString();

Lastly, we will display this text to the user. We will do this using a toast. A toast is a little notification that you can display to user. If you have used android before, you've probably seen this type of notification at least once. go ahead and type: Toast.makeText(this, "Hello, " + message + "!", Toast.LENGTH_SHORT).show();

In this method, we pass in some context for the app (whose calling Toast.makeText), the message we want to display, and the duration for which this message will be shown.

Tadah! we're done!

#Running your app Now you probably want to run your app. If you have an adroid device and you're on windows, please search for and install the drivers required for your device. If you have an android device and you're on a mac, you can just plug yor device in and it will work. If you don't have an android device, you will need to load an emulator. Don't worry, Android Studio will walk you through this process.

At the top of Android Studio, you should see a green play button. Android Studio will now ask you which device you would like to run your app on. If your device is connected, you can choose that. Otherwise, you can create a new virtual device and android studio will use that.

#Resources There are unlimited resources for learning Android Development on the web. I highly recommend learning about Android's activity lifecycle first. From there, you can learn about having apps with multipule activities. Afterwards you should learn about the different UI components (Especially different layouts) and additional cool features like networking. Of course, you can learn some of these things by continueing to attend our meetings.