Put your Activity on a Diet

This talk to share the journey we took at SoundCloud to break our activities and fragments into small components easier to unit test.

Transcript

1. Droidcon Berlin
2. Put your Activity on a Diet Guillaume Lung Pedro Lopes
3. [...] @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.container_layout); connectivityListener.registerHandler(connHandler, CONNECTIVITY_MSG); mUnauthoriedRequestReceiver = new UnauthorisedRequestReceiver (getApplicationContext(), getSupportFragmentManager()); setVolumeControlStream(AudioManager.STREAM_MUSIC); registerReceiver(mLoggingOutListener, new IntentFilter(Actions. LOGGING_OUT)); mOnCreateCalled = true; mIsFirstRun = savedInstanceState == null; } [...] Fat activities title, date, 01 of 10
4. Fat activities title, date, 01 of 10 • Mixture of concerns • Untested
5. [...] @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.container_layout); networkConnectivityController.onCreate(); unauthorisedRequestController.onCreate(getApplicationContext(), ...); screenStateProvider.onCreate(savedInstanceState); setVolumeControlStream(AudioManager.STREAM_MUSIC); } [...] Separation of concerns title, date, 01 of 10
6. [...] @Test public void isNotForegroundOnPause() { screenStateProvider.onResume(activity); screenStateProvider.onPause(activity); expect(screenStateProvider.isForeground()).toBeFalse(); } [...] Testing the logic title, date, 01 of 10
7. Problems title, date, 01 of 10 • Boiler plate • No contract • Error prone [...] public void onPause() { screenStateProvider.onResume(activity); } [...]
8. Solutions title, date, 01 of 10 • Application. ActivityLifecycleCallbacks (only API 14+) • No standard solution yet
9. Solutions title, date, 01 of 10 public class ActivityLightCycleDispatcher { ... } public void add(ActivityLightCycle lightCycle) { ... } public void onCreate(Activity activity, Bundle bundle) { ... } public void onResume(Activity activity) { ... } [...] } public interface ActivityLightCycle { void onCreate(Activity activity, Bundle bundle); void onResume(Activity activity); [...] }
10. public class LightCycleActivity extends Activity implements LightCycleDispatcher { public void attach(ActivityLightCycle lightCycle) { dispatcher.add(lightCycle); } protected void onCreate(Bundle savedInstanceState) { dispatcher.onCreate(this, savedInstanceState); } [...] } Separation of concerns title, date, 01 of 10
11. public class MyActivity extends LightCycleActivity { [...] public MyActivity() { attach(networkConnectivityLightCycle); attach(unauthorisedRequestLightCycle); attach(screenStateLightCycle); } @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.container_layout); setVolumeControlStream(AudioManager.STREAM_MUSIC); } [...] } Separation of concerns title, date, 01 of 10
12. Apply LightCycle to the code base title, date, 01 of 10 • All components implement the same interface • Add tests when extracting • Hook up light cycles in the base activity
13. There is still some boiler plate. title, date, 01 of 10 public class MyActivity extends LightCycleActivity { [...] public MyActivity() { attach(networkConnectivityLightCycle); attach(unauthorisedRequestLightCycle); attach(screenStateLightCycle); }
14. There is still some boiler plate title, date, 01 of 10 public class MyActivity extends LightCycleActivity { @LightCycle NetworkConnectivityLightCycle networkConnectivityLightCycle; @LightCycle UnauthorisedRequestLightCycle unauthorisedRequestLightCycle; @LightCycle ScreenStateLightCycle screenStateLightCycle; public MyActivity() { LightCycleBinder.bind(this); } [...] }
15. Responsabilities title, date, 01 of 10 • Activities ◦ thin component ◦ hook up light cycle components • LightCycles ◦ Do one thing ◦ Agnostic to the Activity they are attached to. ◦ Independent from the others ◦ Platform independant as much as possible ◦ Tested
16. More title, date, 01 of 10 • Works for fragments too • You can build it if you need it (< 1000 lines). • Maybe open sourced (TBD)
17. Thanks! Questions ?