Lecture 2

Lecture material

• Example application we developed in class. To import it in Eclipse, unzip it, then select File > New > Other > Android > Android Project from Existing Code, choose the root directory of the project (it will be called welcome), and Finish.
• Slides of the lecture. We will cover some of these slides next time.
• Video of the lecture.

Homework 1

Due: Thursday January 17. Firm deadline. You will need to submit an .apk and a .zip source ball; detailed instructions for submission will be posted shortly. For this, you will need to have Eclipse, the Android SDK, etc etc, all running, so I highly advise you to get your environment setup as soon as possible. Don't wait until next week!

You must develop a sheep-counting application, for all the smartphone-wielding shepherds out there.

The application must have three buttons:

• +1 (to increment the number of sheeps entering an enclosure)
• -1 (in case some sheep jumps over the fence and out of the enclosure)
• RESET (to reset the count to 0).

The application must also have a counter readout.

The buttons control the readout, quite obviously.

The basic task is to create the app. But, don't stop there: for extra credit, make it nice. Make the buttons nice and big, experiment with their color. Make the readout big and easy to read. Use a sheep photo (with a license allowing reuse) as icon or draw your own.

For the counter, you can use a private int variable in the Application class. This is not ideal, since if the application is destroyed by Android (e.g., because inactive for a while), the counter value is lost. I will teach you later in another class how to make the value persistent, but if you are curious, in this case I would use preferences, as in:

Put this in the Activity class declaration:

private static final String PREFS_NAME = "BasicPreferences";

private static final String SHEEP_COUNT_PREFERENCE_NAME = "sheepCount";

Put this somewhere in onStart:

SharedPreferences settings = getSharedPreferences(PREFS_NAME, 0); 

sheepCount = settings.getInteger(SHEEP_COUNT_PREFERENCE_NAME, 0);

Put this somewhere in onStop:

SharedPreferences settings = getSharedPreferences(PREFS_NAME, 0);

SharedPreferences.Editor editor = settings.edit();

editor.putInteger(SHEEP_COUNT_PREFERENCE_NAME, sheepCount);

editor.commit();

Again, you don't have to do this. I am just telling you in case you are curious.