Fragments Aren't The Only Way

A brief summary of alternatives to using Fragments for Android UI

Transcript

1. Fragments Aren’t The Only Way Brandon Gogetap
2. What are Fragments? • “Represent a behavior or portion of user interface in an Activity”
3. What are Fragments? • “Represent a behavior or portion of user interface in an Activity” • Used to compose a modular UI • One fragment may only be a piece of what the user sees on screen
4. What are Fragments? • “Represent a behavior or portion of user interface in an Activity” • Used to compose a modular UI • One fragment may only be a piece of what the user sees on screen • Receive lifecycle callbacks to allow state saving
5. What are Fragments? • “Represent a behavior or portion of user interface in an Activity” • Used to compose a modular UI • One fragment may only be a piece of what the user sees on screen • Receive lifecycle callbacks to allow state saving • Meant to be reusable across different activities
6. What is the FragmentManager? • Maintains a history/back stack for navigation
7. What is the FragmentManager? • Maintains a history/back stack for navigation • Allows you to replace/add fragments to the UI
8. What is the FragmentManager? • Maintains a history/back stack for navigation • Allows you to replace/add fragments to the UI • Can be used to find fragments that exist in the back stack
9. Some developer.android.com suggestions • Your activity can call methods in the fragment by acquiring a reference…
10. Some developer.android.com suggestions • Your activity can call methods in the fragment by acquiring a reference… • ExampleFragment fragment = (ExampleFragment) getFragmentManager().findFragmentById(R.id.example_fragment);
11. Some developer.android.com suggestions • Your activity can call methods in the fragment by acquiring a reference… • ExampleFragment fragment = (ExampleFragment) getFragmentManager().findFragmentById(R.id.example_fragment); • In some cases, you might need a fragment to share events with the activity…
12. Some developer.android.com suggestions • Your activity can call methods in the fragment by acquiring a reference… • ExampleFragment fragment = (ExampleFragment) getFragmentManager().findFragmentById(R.id.example_fragment); • In some cases, you might need a fragment to share events with the activity… • Create Interface that your Activity implements
13. Some developer.android.com suggestions • Your activity can call methods in the fragment by acquiring a reference… • ExampleFragment fragment = (ExampleFragment) getFragmentManager().findFragmentById(R.id.example_fragment); • In some cases, you might need a fragment to share events with the activity… • Create Interface that your Activity implements • Activity should coordinate communication between fragments
14. Some developer.android.com suggestions public static class FragmentA extends ListFragment {
 
 private OnArticleSelectedListener listener;
 
 // Container Activity must implement this interface
 public interface OnArticleSelectedListener {
 public void onArticleSelected(Uri articleUri);
 }
 
 @Override public void onAttach(Context context) {
 super.onAttach(context);
 try {
 listener = (OnArticleSelectedListener) context;
 } catch (ClassCastException e) {
 throw new ClassCastException(context.toString() + " must implement OnArticleSelectedListener");
 }
 }
 }
15. Some developer.android.com suggestions public static class FragmentA extends ListFragment {
 
 private OnArticleSelectedListener listener;
 
 // Container Activity must implement this interface
 public interface OnArticleSelectedListener {
 public void onArticleSelected(Uri articleUri);
 }
 
 @Override public void onAttach(Context context) {
 super.onAttach(context);
 try {
 listener = (OnArticleSelectedListener) context;
 } catch (ClassCastException e) {
 throw new ClassCastException(context.toString() + " must implement OnArticleSelectedListener");
 }
 }
 }
16. Some developer.android.com suggestions
17. Google suggestion summary • Activity A should coordinate communication between Fragment A and B
18. Google suggestion summary • Activity A should coordinate communication between Fragment A and B • Activity A has logic tied to Fragment B
19. Google suggestion summary • Activity A should coordinate communication between Fragment A and B • Activity A has logic tied to Fragment B • Activity B (containing Fragment B) should be used on phone-sized devices
20. Google suggestion summary • Activity A should coordinate communication between Fragment A and B • Activity A has logic tied to Fragment B • Activity B (containing Fragment B) should be used on phone-sized devices • Activity B has logic tied to Fragment B
21. What are Fragments? • “Represent a behavior or portion of user interface in an Activity” • Used to compose a modular UI • One fragment may only be a piece of what the user sees on screen • Receive lifecycle callbacks to allow state saving • Meant to be reusable across different activities
22. What are Views? • “Represent a behavior or portion of user interface in an Activity” • Used to compose a modular UI • One view may only be a piece of what the user sees on screen • Receive lifecycle callbacks to allow state saving • Meant to be reusable across different activities
23. Custom views as UI building blocks • Pros
24. Custom views as UI building blocks • Pros • Simple lifecycle
25. Custom views as UI building blocks • Pros • Simple lifecycle • Promotes use of Presenter
26. Custom views as UI building blocks • Pros • Simple lifecycle • Promotes use of Presenter • Cons
27. Custom views as UI building blocks • Pros • Simple lifecycle • Promotes use of Presenter • Cons • No back stack API provided for you
28. Custom views as UI building blocks • Implementing your own back stack gives full control of API you’ll be using for, potentially, years
29. Custom views as UI building blocks • Implementing your own back stack gives full control of API you’ll be using for, potentially, years • You know when events are going to happen
30. Custom views as UI building blocks • Implementing your own back stack gives full control of API you’ll be using for, potentially, years • You know when events are going to happen • Fragment API history riddled with unpredictable callbacks
31. Custom views as UI building blocks • Implementing your own back stack gives full control of API you’ll be using for, potentially, years • You know when events are going to happen • Fragment API history riddled with unpredictable callbacks • IllegalStateException says Hi
32. Custom views as UI building blocks • Implementing your own back stack gives full control of API you’ll be using for, potentially, years • You know when events are going to happen • Fragment API history riddled with unpredictable callbacks • IllegalStateException says Hi • As with any in-house API, updates are under your control
33. Security side note • isValidFragment • PreferenceActivity susceptible to “Fragment Injection” https://securityintelligence.com/new-vulnerability-android-framework-fragment-injection/
34. Custom views as UI building blocks • Maybe not the best choice for quick apps • Though you could make a library to be shared easily among different apps
35. Custom views as UI building blocks • Maybe not the best choice for quick apps • Though you could make a library to be shared easily among different apps • Longer initial implementation
36. Custom views as UI building blocks • Maybe not the best choice for quick apps • Though you could make a library to be shared easily among different apps • Longer initial implementation • Boilerplate
37. Custom views as UI building blocks • BackStack class holds Set of back stack objects
38. Custom views as UI building blocks • BackStack class holds Set of back stack objects • Activity attaches to specialized Presenter-type class which controls navigation
39. Custom views as UI building blocks • BackStack class holds Set of back stack objects • Activity attaches to specialized Presenter-type class which controls navigation • Activity handles creating views defined in BackStack items • Also in charge of animating views in/out
40. Custom views as UI building blocks • BackStack • Contains a Set of objects responsible for inflating Views • May define things such as animation/dagger scope • Ideally can be rebuilt from Bundle
41. Custom views as UI building blocks • UI Manager class (specialized Presenter) • Passes on push/pop transactions to Activity • The interface for interacting with the back stack for the rest of your app
42. Conductor • Open source back stack management framework
43. Conductor • Open source back stack management framework • Simple lifecycle
44. Conductor • Open source back stack management framework • Simple lifecycle • Customizable transitions
45. Conductor • Open source back stack management framework • Simple lifecycle • Customizable transitions • Easy state persistence
46. Conductor • Controllers
47. Conductor • Controllers • Building block of Conductor’s back stack
48. Conductor • Controllers • Building block of Conductor’s back stack • Similar to Fragments in that they are wrappers around View inflation
49. Conductor • Controllers • Building block of Conductor’s back stack • Similar to Fragments in that they are wrappers around View inflation • Callbacks for permission results/activity result/etc.
50. Conductor • Controllers • Building block of Conductor’s back stack • Similar to Fragments in that they are wrappers around View inflation • Callbacks for permission results/activity result/etc. • Highly streamlined lifecycle
52. Conductor • Router
53. Conductor • Router • Analog to FragmentManager
54. Conductor • Router • Analog to FragmentManager • Coordinates the pushing/popping of Controllers onto back stack
55. Conductor • Router • Analog to FragmentManager • Coordinates the pushing/popping of Controllers onto back stack • Transitions are defined in RouterTransactions
56. Conductor RouterTransaction.with(new HomeController())
 .pushChangeHandler(new FadeChangeHandler())
 .popChangeHandler(new FadeChangeHandler());
57. Conductor • Overall, shares a similar pattern with Fragments/FragmentManager • Main benefits • Simplified lifecycle • Easily customizable transitions
58. Flow • Developed by Square • Back stack management composed of “Keys” • Full control over back stack (easy to populate a back stack from scratch) • A good chunk of boilerplate required for setup
59. Scoop • Developed by Lyft • Uses “Screen”s that define “ViewController”s • Also gives full control over back stack history • Gives easy access to “scopes” to assist in dependency injection • Customizable transitions • Annotation-based
60. References Fragment Docs https://developer.android.com/guide/components/fragments.html Conductor https://github.com/bluelinelabs/Conductor Flow https://github.com/square/flow Scoop https://github.com/lyft/scoop