Android Tutorial 2

0.1 | Load Project

• Start Android Studio

• Select checkout from version control and choose git

• Paste in the URL: https://github.com/RobRoseKnows/hackumbc-tutorial.git

• Press clone and select YES

• Import project from external model

• Select default gradle wrapper and hit OK

• Wait for the project to build

• Make sure both are selected and hit OK

• Setup Frameworks will pop up and Hit OK

0.2 | Open Emulator or Connect Phone

If you have an Android device:

• Go to your device's About screen and tap the build number a bunch of times.
• You are now should have the developer menu available, open it and enable USB Debugging
• Plug in your device to your computer using a Micro-USB cable
• If it asks for authorization, click yes.

If you do not have an Android device:

• Open the Android Virtual Device Manager (AVD)
• Either create a new AVD with an API version of at least 19
• Do not choose an Intel processor.
• Open the virtual device and leave it open. That saves time.

0.3 | Stuff I Did Beforehand

• Designed the activity_main.xml file.
  • Created a TextView with the ID gpa_text
  • Created a ListView with the ID class_list
  • Created a Button with the ID create_button
• It's a relative layout, you can see some of the examples of ways to organize them.
• Added String resources.
  • The current_gpa string resource has formatting markup.

0.4 | The Android APK

• I am not an expert on the inner workings of Android but here's what I do know:
• The Android APK contains a bunch of things that make up an Android app.
• I'm going to refer you to Wikipedia
  • You should also looks at the android documentation found at .
• Contains:
  • META-INF: the manifest, and the certificates and hashes
  • lib: Processor-specific code
  • res: Contains the resources not compiled into resources.arsc
  • assets: contains things like images, icons, etc.
  • AndroidManifest.xml: meta-data for the Android app.
  • classes.dex: Everything compiled together
  • resources.arsc: Resources pre-compiled
• All this compilation happens when the app is opened for the first time.
• There's one important file called R.java that contains references to where the program can find all the views, resources, etc.

1.1 | Views

• A View is an Object that is the super class of all things drawable in Android
• Some subclasses of Views are:
  • TextView
  • ProgressBar
  • ImageView
  • ViewGroup
• Even Layouts are views, they are sub classes of the subclass ViewGroup.

1.1.1 | Layouts

• Layouts are ViewGroups, they hold a bunch of view in a nested way.
• You define layouts in XML files, it's easier than the design mode once you get the hang of it
• If you are familiar with AWT or Swing, many of the same layouts you find there you can find in Android.
• Layouts Include:
  • https://developer.android.com/reference/android/widget/FrameLayout.html
  • LinearLayout
  • RelativeLayout
• Those are just a few of them.

1.1.2 | Getting Views in Code

• Views wouldn't be very helpful if we weren't able to manipulate them in code.
• So we need to use findViewById() to get the View Object.
• findViewById() returns a View object though, we need to cast it to the type we want
• R.java gives us access to all the ids

gpaTextView = (TextView) findViewById(R.id.gpa_text);
classListView = (ListView) findViewById(R.id.lecture_list);
addClassButton = (Button) findViewById(R.id.create_button);

1.1.3 | Create a View

• We create a new XML file to create a View to hold each lecture.

2.1 | Working with data

• Now we're going to populate the ListView with some of our data.
• We have data already in the form of the exampleClassesArray and exampleClassesList.
• We're going to put this into the classListView ListView.
• We need to use an ArrayAdapter
  • But first we need a View.

2.1.1

ArrayAdapter<String> itemsAdapter = 
    new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, items);