Basic Information

• Supports Android API 15 - 22 (no need for support package)
• Using 3 libraries
  • Android Annotation
  • Butterknife
  • Logger
• Color themed after Realm CI
• API 15-20 follows Holo design
• API 21-22 follows Material design

UI

• Two button at the bottom
  • First
  • Second
• One textview for counter
  • It is at the center of the view below toolbar (or action bar) and above buttons

Counter

Counter Policy

• Keep the value if the app is rotated
• Keep the value if the app is in background
• Reset the value if the app is killed

Counter Interface

public void increment(); public int getValue(); public void setValue(int value); public void reset();

Counters

• IntegerCounter
  • using primitive int value, which is not-thread safe
• AtomicIntegerCounter
  • using AtomicInteger which already is thread-safe
• SynchronizedMethodCounter
  • using primitive int value, but all the methods are synchronized
• SynchronizedObjectCounter
  • using primitive int value, but all the codes in the method are synchronized
• PreferenceCounter
  • using SharedPreference which already is thread-safe, not process-safe though
• SQLCounter
  • using SQLite, which is not thread-safe

Worker

Worker Policy

• Toggle worker if the second button is pressed
• Stop worker is the app is in background, start back if the app came back to foreground
• It the worker was running, re-create the worker when the app is created again
• If the worker was running, re-create the worker if the app is rotated (the consumed time won’t be reserved)

Worker Interface

public void start(WorkerListener listener); public void stop(); public boolean isRunning();

WorkerListener

• Send event to increase counter value by one

public interface WorkerListener {
    public void work();
}

Workers

• ThreadWorker
  • Using thread
• AsyncWorker
  • Using AsyncTask
• TimerWorker
  • Using Timer

There are 6 kinds of counters and 3 kinds of workers. You can pick one of the counter and one of the worker from “initializeCounter” and “initializeWorker” methods.

Android Life Cycle

• Activity Created
  • onCreate
  • onResume
  • onPause
  • onDestroy
• Device Rotation
  • onPause
  • onSaveInstanceState
  • onDestroy
  • onCreate
  • onRestoreInstanceState
  • onResume

Why it is thread safe

• All of the method for counter are executed in Main Thread.
• Some of the counter is already thread-safe, so you can use the method in any thread.

Android Test

• How to run

$./gradlew connectAndroidTest

• Testing whether the Counter class is thread-safe
• Some of the counter class is thread-safe and some are not as expected
• There will be 100 threads running increment method
• There will be 1000 times increment
• If the value is 1000 after all of the increments are done, it is succeeded.
• For IntegerCounter, AtomicIntegerCounter, SynchronizedMethodCounter, SynchronizedObjectCounter I made is 100000 times of increment since the integer calculation is so fast.

Test Result

• PreferenceCounter, SQLCounter, IntegerCounter is not thread-safe
• SQL is know to be not thread-safe, also there were way over database execution, so that the process crashed.
• Shared Preference is know to be thread-safe, but code I wrote on PreferenceCounter wasn't thread-safe. getValue() in the middle makes the code not to be thread-safe.

SharedPreferences.Editor edit = getInstance().edit();
edit.putInt(COUNTER, getValue() + 1);
edit.apply();

• To make PreferenceCounter to be thread safe, I have to make all the method to be synchronized.
• IntegerCounter is not thread-safe as expected. But the calculation is so fast, usually it won't cause any problem.

3rd Party libraries

• Support Annotation

  • New annotation package with number of useful metadata annotation.

• Butterknife

  • Automatically inject views in layout to corresponding object using @Injectview annotation.
  • Helps to reduce code line and increase code readability.

• Logger

  • Simple, pretty, powerful logger for Android.
  • Shows thread, class, method information.

Author

Fullname : Leonardo Taehwan Kim
Username : The Finest Artist
Email : [email protected]