CS 185C/286 - Lecture 1

Cay S. Horstmann

Lecture 1 Quiz 1

Put your answer into Piazza.

Which of the following is true according to Programming Android Chapter 1?

1. You should use OpenJDK, not the Oracle JDK, for Android programming.
2. You should install Eclipse in your home directory, not in /opt.
3. The ADT can be installed into Eclipse, NetBeans, or IDEA.
4. To run your app on your phone, you must first become a registered developer.

Android Components

• Operating system (Linux kernel)
• Hardware support: Camera, GPS, accelerometer
• Telephony (voice and data) and Wifi
• Custom 2D graphics library, OpenGL based 3D graphics
• Dalvik VM
• Application framework
• Core apps: webkit-based browser, contacts, etc.
• Media support, including H.264
• SQLite database

Android History

• 2003 - Android Inc. startup founded
• 2005 - Google buys Android Inc.
• 2008 - Android 1.0 released
• 2009 - Android 1.1, 1.5, 1.6, 2.0, 2.1
• 2010 - Android 2.2, 2.3
• 2011 - Android 3.0 (tablets only)
• 2011 - Android 4.0, unifies 2.3 and 3.0
• 2012 - Android 4.1, AKA Jelly Bean

Android and Java

• Use Java to write Android applications
• Subset of standard Java library, adapted from Apache Harmony
• Application framework completely different from standard Java
• Comparable to Blackberry (pre 10) programming
• Unlike BlackBerry or Java ME phones, no Java Virtual Machine
• Java class files converted to Dalvik VM
• Each app runs in separate Linux process running a Dalvik instance
• Dalvik machine code (DEX) optimized for small memory footprint

Android App Components

• Activity: a UI screen
• Service: lengthy job without UI, e.g. playing music
• Broadcast receiver: reacts to system or app broadcasts
• Content provider: make data available to other apps
• A particular app can have components of some or all of these types
• Each component is a Java class
• No main

Android Development Toolkit (ADT)

• Eclipse based IDE + command line tools
• Runs on Linux, Mac, Windows
• Uses regular Oracle JDK
• Can plug into regular Eclipse
• Easier to download the Eclipse + ADT bundle
• Ok to have multiple versions of Eclipse—even on Windows
• Supports multiple SDK levels
• We'll target 2.2 for our projects since it captures 97% of the market.
• Android Virtual Device (AVD): Phone emulator

git Basics

• Distributed version control system
• We don't care about the “distributed” part—we use a central server
• Very commonly used (Linux kernel, github)
• More flexible than Mercurial, but less user-friendly
• You only need these commands:

  git clone ssh://server.com/reponame
  git pull
  git add [em file]
  git rm [em file]
  git status -s
  git commit -a -m "..."
  git push origin master

• Don't use a command that you “found on the internet”.
• Don't use any options that force or override, even if git suggests them.
• Don't use a GUI client.

Git workflow

• You only clone a repo once.
• Always run git pull before you do anything else
• Run git add to add files to the “staging area”.
• Run git commit -a -m "..." to commit the staged files.
• Run git push origin master to update the server.
• Version control is only for files that are
  1. not automatically generated
  2. platform-independent
• Use .gitignore to list files that should not be checked in.

Lab

• Bring your laptop to the lab
• You will work with a buddy
• One of you writes code, the other types up answers
• Switch roles each lab
• Submit lab work to git

Checking out Your Repo

1. In your home directory, run

   git clone ssh://git@zoidberg.cs.sjsu.edu:62222/Lastname_Firstname cs185c

   What happens?

   If you got a warning, that's ok. But if you got an error, that needs to be fixed before you can go on.

2. Run

   ls -a cs185c

   What do you get?

Getting Started with Android Programming

1. Run ~/adt-bundle-linux-x86/eclipse/eclipse
2. Create ~/cs185c/workspace as your workspace
3. Select File -> New Android Application
4. App name lab01, everything else default
5. Next, next, next...finish
6. Close welcome screen to see your project
7. srcis the Java source, res are the UI resources
8. What source files were generated by the wizard?
9. Where does the "Hello, World" message come from?
10. Where is the class R defined?

Running Your Program

1. Run your program by clicking on the green Run button or selecting Run from the Project menu. What happens?
2. Click Next.
3. Select Launch a new Android Device. What happens?
4. Click on the Manager button, then on New
5. Set the AVD name to nexussand choose Nexus S for the device
6. Click Ok, close the device manager. Click Refresh
7. Run the program again. What happens?

Changing the Message

We want to change the message to Hello, Dave.

1. Does the application source file contain the string "Hello, World"?
2. Click on activity_main.xml in the Package Explorer and then on the activity_main.xml tab next to the Graphical Layout tab. What do you see?
3. What happens if you change @string/hello_world to @string/hello_dave?
4. Ok, that couldn't have worked. Look inside values/strings.xml. What do you see?
5. How do you change the message? Be sure to run the app.
6. Why do you think that the message wasn't stored directly in the activity_main.xml file?

An image

We want to add an image. Here's one of Dave.

1. Move the image to the ~/cs185c/workspace/lab01/res/drawable-hdpi directory.
2. Go to activity_main.xml and click on the Graphical Layout tab. Select Images & Media and drag an ImageView on the screen. What happens when you drop it?
3. Hook up the 2001_dave.jpg file.
4. Try running the app. What happens?
5. Look in the Problems tab. What's the problem?
6. Double-click on the error message. What's really the problem?
7. Why shouldn't you fix it by editing R.java?
8. How can you fix the problem?
9. Now run the program. What happens?

Checking in a Project

1. Run find cs185c. What do you get?
2. What bad thing would happen if you checked all these files into version control?
3. Give an example of an automatically generated file that should not be checked in.
4. Give an example of a platform-dependent file that should not be checked in. (You may need to poke into some Eclipse files with a text editor.)
5. To make sure that you don't check in inappropriate files, place a file named .gitignore into the ~/cs185c directory. Note the dot in .gitignore. The file should contain the following:

   workspace/.metadata
   workspace/*/local
   workspace/*/local.properties
   workspace/*/bin
   workspace/*/gen
   .DS_Store

   Now run git add workspace/lab01 and git status -s in the ~/cs185c directory. What happens?

   You should see a listing of files that haven't yet been submitted to version control. None of them should be class files, metadata files, or generated files. Check with me if this looks wrong.

6. Run

   git commit -a -m "Done with lab 1"
   git push origin master

   What happens?
7. To see that you did it right, change to /tmp and clone your repo again. How did you do that?
8. What files did you get?

Reading Before Next Class

• Programming Android Ch. 5