Programming for Android - more than basics Tomáš Kypta @TomasKypta Agenda • Material design • UX design patterns • Dialogs • Notiﬁcations • Broadcast receiver • Service Agenda • Fragment • Process & memory • Background processing • Loader • Software design patterns Material Design Android Design Evolution long time ago … Android Design Evolution Holo Design Material Design Material Design Material Design • tangible surfaces and edges • shadows • elevation • motion Material Design • themes since API level 21 • @android:style/Theme.Material (dark version) • @android:style/Theme.Material.Light (light version) • @android:style/Theme.Material.Light.DarkActionBar • … Material Design • compatibility themes • @style/Theme.AppCompat (dark version) • @style/Theme.AppCompat.Light (light version) • @style/Theme.AppCompat.Light.DarkActionBar • … The Color Palette • three color hues from primary palette • one accent color from the secondary palette The Color Palette • http://www.google.com/ design/spec/style/color.html The Color Palette     The Color Palette     The Color Palette Toolbar Toolbar • generalization of action bar • main Android navigation element Toolbar • ActionBarActivity compile 'com.android.support:appcompat-v7:22.0.0' • inherit styles from Theme.AppCompat • for inﬂating views for action bar use getSupportActionBar().getThemedContext() Toolbar Toolbar @Override  protected void onCreate(Bundle savedInstanceState) {  super.onCreate(savedInstanceState);  setContentView(R.layout.activity_main);    Toolbar toolbar = (Toolbar) findViewById(R.id.my_toolbar);  setSupportActionBar(toolbar);  } Toolbar • standalone mode • setSupportActionBar(toolbar); CardView CardView • showing information inside cards with consistent look compile 'com.android.support:cardview-v7:22.0.0' CardView CardView     …   Elevation Elevation Elevation android:elevation=“4dp” view.setElevation(elevation); Transition Transition Animation • since API level 21 @android:transition/explode  @android:transition/explode Transition public class MyActivity1 extends ActionBarActivity {  @Override  protected void onCreate(Bundle savedInstanceState) {  // enable transitions before content is added getWindow().requestFeature( Window.FEATURE_CONTENT_TRANSITIONS);   super.onCreate(savedInstanceState);  setContentView(R.layout.activity_my_1);  …  }  } Transition btn.setOnClickListener(new View.OnClickListener() {  @Override  public void onClick(View v) {  getWindow().setExitTransition(new Explode());  Intent intent = new Intent(MyActivity1.this, MyActivity2.class);  startActivity(intent,  ActivityOptions  .makeSceneTransitionAnimation(MyActivity1.this) .toBundle());  }  }); Shared Element Transition • enable window content transitions • transition for shared element • deﬁne shared element with android:transitionName • in both layouts • ActivityOptions.makeSceneTransitionAnimation() Shared Element Transition Ripple Ripple • RippleDrawable • set as view background Ripple Ripple     Dynamic color State List Animator State List Animator • materials raise up to meet your ﬁnger • android:stateListAnimator="@anim/raise" State List Animator … and ripple State List Animator                 UX Design Patterns Pull-to-Refresh         Pull-to-Refresh Navigation Drawer • panel that transitions from the left edge of the screen • displays the app’s main navigation options Multi-pane Layouts Multi-pane Layouts • many different screen sizes and types of devices • provide balanced and aesthetically pleasing layout Multi-pane Layouts • do not forget different orientations • various strategies Multi-pane Layouts Swipe Views Swipe Views Swipe Views • allow efﬁcient navigation between items • swiping between detail views • swiping between tabs Swipe-to-dismiss Swipe-to-dismiss • dismiss list item by swiping left or right Swipe-to-dismiss with Undo Dialogs Dialogs • via DialogFragment • styling problems Dialogs Dialogs • android-styled-dialogs • https://github.com/avast/android-styled-dialogs Dialogs SimpleDialogFragment.createBuilder(c, getSupportFragmentManager())  .setTitle(“Backport of material dialogs")  .setMessage(“Lorem ipsum dolor sit amet…”)  .setPositiveButtonText("OK")  .setNegativeButtonText("Cancel")  .setNeutralButtonText("Help")  .setRequestCode(REQUEST_SIMPLE_DIALOG)  .show(); Dialogs •implement listener in activity/fragment to receive callback •ISimpleDialogListener •IPositiveButtonDialogListener •INegativeButtonDialogListener •INeutralButtonDialogListener Dialogs @Override  public void onPositiveButtonClicked(int requestCode) {  if (requestCode == REQUEST_SIMPLE_DIALOG) {  Toast.makeText(c, "Positive button clicked", Toast.LENGTH_SHORT) .show();  }  } Notiﬁcation Notiﬁcation • a message that can be displayed to the user outside your normal UI • displayed in notiﬁcation area Notiﬁcation • user can open notiﬁcation drawer to see the details • app can deﬁne UI and click action • NotificationCompat.Builder Notiﬁcation NotificationCompat.Builder mBuilder =  new NotificationCompat.Builder(this)  .setSmallIcon(R.drawable.icon)  .setContentTitle("My notification")  .setContentText("Hello World!"); Notiﬁcation Intent resultIntent = new Intent(this, MyActivity1.class);    TaskStackBuilder stackBuilder = TaskStackBuilder.create(this);   stackBuilder.addParentStack(MyActivity1.class);  stackBuilder.addNextIntent(resultIntent); Notiﬁcation PendingIntent resultPendingIntent =  stackBuilder.getPendingIntent(  0,  PendingIntent.FLAG_UPDATE_CURRENT  );  mBuilder.setContentIntent(resultPendingIntent);   NotificationManager mNotificationManager =  (NotificationManager) getSystemService( Context.NOTIFICATION_SERVICE);   mNotificationManager.notify(MY_ID, mBuilder.build()); Notiﬁcation • update notiﬁcation by using the same ID Broadcast Receiver Broadcast Receiver public class MyReceiver extends BroadcastReceiver {    @Override  public void onReceive(Context context, Intent intent) {  // do something  }  } Broadcast Receiver • don’t do any threading in onReceive() • start a service instead and do the threading there Dynamic Registration context.registerReceiver(mReceiver, new IntentFilter(Intent.ACTION_SEND)); context.unregisterReceiver(mReceiver); Service Service • component for background processing • android.app.Service • two forms • started service • bound bound Service • by default runs on the main thread! Started Service • to perform some operation without returning result to the caller • start by calling context.startService(Intent) • only one instance of the service is created Started Service @Override  public int onStartCommand(Intent intent, int flags, int startId) {  if (ACTION_DO_SOMETHING.equals(intent.getAction())) {  // do something }  return super.onStartCommand(intent, flags, startId);  } Started Service • service has to be stopped after processing the request • otherwise it lives indeﬁnitely • stopSelf() • stopSelf(int) • stopService(Intent) Bound Service • for interacting with other components • to expose functionality to other apps • client calls bindService() • cannot be called from broadcast receiver Bound Service • implement onBind() • return null if you don’t want to allow binding Bound Service • clients call unbindService() • when all clients are unbound, the system destroys the service • no need to stop service explicitly Service • Started and Bound approaches can be mixed Service Lifecycle • service lifetimes: • entire lifetime • active lifetime • start in onStartCommand() or onBind() Service Lifecycle Foreground Service • something user is actively aware of • must provide an ongoing notiﬁcation • cannot be dismissed • startForeground() • stopForeground() Intent Service Intent Service • service for processing on background threads • for processing independent on UI • android.app.IntentService Intent Service public class MyIntentService extends IntentService {    public MyIntentService() {  super("MyIntentService");  }    @Override  protected void onHandleIntent(Intent intent) {  // run some code on background  }  } Fragment Fragment • represents a behavior or a portion of user interface in an activity • multiple fragments can be combined in a single activity Fragment Activity & Fragment • add in the layout Activity & Fragment • add programmatically FragmentManager fragmentManager = getFragmentManager() FragmentTransaction transaction = fragmentManager.beginTransaction(); ExampleFragment fragment = new ExampleFragment(); transaction.add(R.id.fragment_container, fragment); transaction.commit(); Fragment Back Stack • fragments can be kept in a stack FragmentManager fragmentManager = getFragmentManager() FragmentTransaction transaction = fragmentManager.beginTransaction(); ExampleFragment fragment = new ExampleFragment(); transaction.add(R.id.fragment_container, fragment); transaction.addToBackStack(null); transaction.commit(); Fragment Back Stacks A A B A B C A B back Fragment Lifecycle Fragment Lifecycle • a bit more complicated than activity lifecycle Fragment Lifecycle Fragment Lifecycle Activity & Fragment Lifecycle Activity & Fragment Lifecycle Fragment Lifecycle Callbacks onAttach() • fragments associated with the activity onCreateView() • create fragment’s view hierarchy here onActivityCreated() • activity’s onCreate() method has returned Fragment Lifecycle Callbacks onDestroyView() • view hierarchy is being removed onDetach() • fragment is being disassociated from the activity Fragment without a UI • aka worker fragment transaction.add(workFragment, “work”); Process & Memory Process • application starts with one Linux process with single thread • system can shut down a process when memory is low Process • foreground process • visible process • service process • background process • empty process Memory State @TargetApi(Build.VERSION_CODES.ICE_CREAM_SANDWICH)  @Override  public void onTrimMemory(int level) {  super.onTrimMemory(level);  if (level >= TRIM_MEMORY_COMPLETE) {  // they will kill us soon!  }  if (level >= TRIM_MEMORY_UI_HIDDEN) {  // release all UI related memory  }  // more levels  } Memory State • retrieve current trim level at any time • ActivityManager.getMyMemoryState(RunningAppProcessInfo) Background Processing Threads • main thread = UI thread • never block the UI thread!!! • use worker threads for time consuming operations • networking, db, ﬁlesystem, … • UI toolkit is not thread safe • never manipulate UI from a worker thread!!! Threads • complications • activities are restarted • memory leaks • crashes Background Processing • Thread • AsyncTask • IntentService • Loader • ThreadPoolExecutor • AbstractThreadedSyncAdapter Background Processing Some people, when confronted with a problem, think, "I know, I'll use threads," and then two they hav erpoblesms. HandlerThread HandlerThread • holds a queue of tasks • other threads can push tasks to it • the thread processes its queue, one task after another • when the queue is empty, it blocks until something appears Looper and Handler • Looper • class that runs a message loop for a thread • Handler • provides interaction with the message loop Looper and Handler • sendMessage(Message) • Message object, retrieve with Message.obtain() • post(Runnable) • delayed versions, at time versions Looper and Handler • UI thread has Looper • you can create easily another Handler • Handler is bound to the Looper of the current thread • or you can explicitly provide different Looper Loader Loader • asynchronous loading of data • bound to activity or fragment • monitor source of data, deliver changes • reconnect after conﬁg change, don’t need to requery • managed by LoaderManager Loader • AsyncTaskLoader • CursorLoader Loader • you have to implement LoaderManager.LoaderCallbacks Loader @Override  public Loader onCreateLoader(int id, Bundle args) { // instantiate a new loader  return null;  }    @Override  public void onLoadFinished(Loader loader, D data) {  // called when loader finished its loading  }    @Override  public void onLoaderReset(Loader loader) {  // called when loader is being reset  } Loader @Override  public Loader onCreateLoader(int id, Bundle args) {  return new CursorLoader(getActivity(), mUri, mProjection, "value > ?", new String[]{String.valueOf(5)}, "value ASC”);  } Loader @Override  public void onLoadFinished(Loader loader, Cursor cursor) {  mAdapter.swapCursor(cursor);  }    @Override  public void onLoaderReset(Loader loader) {  mAdapter.swapCursor(null);  } Loader // prepare the loader  // either re-connect with an existing one,  // or start a new one. getLoaderManager().initLoader(0, null, this); Loader // restart the loader to do a new query   getLoaderManager().restartLoader(0, null, this); Software Design Patterns Component Creation • don’t override constructors • you don’t control component creation • use lifecycle callbacks Simple Dependency Injection • via Context Object context.getSystemService(String) Simple Dependency Injection public class MyApplication extends Application {    private MyManager mMyManager;    @Override  public Object getSystemService(String name) {  if (MyManager.class.getName().equals(name)) {  if (mMyManager == null) {  mMyManager = new MyManager();  }  return mMyManager;  }  return super.getSystemService(name);  }  } Simple Dependency Injection MyManager myManager = (MyManager) context.getSystemService(MyManager.class.getName()); Simple Dependency Injection • can’t be used in libraries • you usualy don’t control the application object View Holder static class ViewHolder {  TextView txtName;  TextView txtDescription;    public ViewHolder(View view) {  txtName = (TextView) view.findViewById(R.id.txt_name);  txtDesc = (TextView) view.findViewById(R.id.txt_desc);  }  } view.setTag(holder); ViewHolder holder = (ViewHolder) view.getTag(); Cross Component Communication Cross Component Communication • broadcast • local broadcast • event bus Local Broadcast Local Broadcast LocalBroadcastManager lbManager = LocalBroadcastManager.getInstance(context); lbManager.registerReceiver(mReceiver, intentFilter); lbManager.unregisterReceiver(mReceiver);   lbManager.sendBroadcast(intent);   lbManager.sendBroadcastSync(intent); Event Bus Event Bus • no direct support • library or custom implementation Event Bus • Otto (http://square.github.io/otto) Bus bus = new Bus();  bus.register(this); bus.unregister(this); @Subscribe  public void wasLoggedOut(LogoutEvent event) {  // do some logout action  } Event Bus bus.post(new LogoutEvent(LogoutEvent.LogoutType.MANUAL)); @Produce  public LogoutEvent produceLogoutEvent() {  return new LogoutEvent(LogoutEvent.LogoutType.MANUAL);  } Questions?