Eliminate RecyclerView Boilerplates

Layout and RecyclerView.ViewHolder binding which uses annotation processor to eliminate RecyclerView boilerplates for Android development.

ViewHolderBinding enables you to eliminate..
- switch or if-else statements for ViewType detection
- layout inflation boilerplate codes
- casting RecyclerView.ViewHolder class for binding layouts and ViewHolders

* GitHub repository
https://github.com/shaunkawano/ViewHolderBinding

* potatotips #37 (iOS/Android開発Tips共有会) - connpass https://potatotips.connpass.com/event/48618/

1. ELIMINATE RECYCLERVIEW BOILERPLATES ΁͍΁͍ @shaunkawano גࣜձࣾτϧς / Android Developer
2. Shohei Kawano @shaunkawano Android Developer at Torte, Inc. About Me
3. Let’s talk about RecyclerView
4. When you use RecyclerView, you need to implement RecyclerView.Adapter
5. RecyclerView.Adapter basic methods
6. RecyclerView.Adapter basic methods void onBindViewHolder(VH holder, int position) VH onCreateViewHolder(ViewGroup parent, int viewType) int getItemViewType(int position) int getItemCount()
7. RecyclerView.Adapter basic methods void onBindViewHolder(VH holder, int position) VH onCreateViewHolder(ViewGroup parent, int viewType) int getItemViewType(int position) int getItemCount()
8. Let’s assume we have R.layout.id as our view type.
9. onCreateViewHolder
10. @Override public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { LayoutInflater inflater = LayoutInflater.from(parent.getContext()); switch (viewType) { case R.layout.row_taro:
 View taroView = inflater.inflate(R.layout.row_taro, parent, false);
 return new TaroViewHolder(taroView);
 case R.layout.row_shiro:
 View shiroView = inflater.inflate(R.layout.row_shiro, parent, false);
 return new ShiroViewHolder(shiroView);
 case R.layout.row_leona:
 View leonaView = inflater.inflate(R.layout.row_leona, parent, false);
 return new LeonaViewHolder(leonaView);
 default:
 throw new IllegalArgumentException(“error message here.”);
 }
 } onCreateViewHolder
11. onBindViewHolder
12. onBindViewHolder @Override public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) { int viewType = getItemViewType(position);
 switch (viewType) { case R.layout.row_taro:
 onBindTaroViewHolder((TaroViewHolder) holder, position); break; case R.layout.row_shiro:
 onBindShiroViewHolder((ShiroViewHolder) holder, position); break; case R.layout.row_leona:
 onBindLeonaViewHolder((LeonaViewHolder) holder, position); break;
 default:
 throw new IllegalArgumentException(“Some message.”);
 } }
13. @Override public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) { int viewType = getItemViewType(position);
 switch (viewType) { case R.layout.row_taro:
 onBindTaroViewHolder((TaroViewHolder) holder, position); break; case R.layout.row_shiro:
 onBindShiroViewHolder((ShiroViewHolder) holder, position); break; case R.layout.row_leona:
 onBindLeonaViewHolder((LeonaViewHolder) holder, position); break;
 default:
 throw new IllegalArgumentException(“Some message.”);
 } } onBindViewHolder
14. @Override public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) { int viewType = getItemViewType(position);
 switch (viewType) { case R.layout.row_taro:
 onBindTaroViewHolder((TaroViewHolder) holder, position); break; case R.layout.row_shiro:
 onBindShiroViewHolder((ShiroViewHolder) holder, position); break; case R.layout.row_leona:
 onBindLeonaViewHolder((LeonaViewHolder) holder, position); break;
 default:
 throw new IllegalArgumentException(“Some message.”);
 } } onBindViewHolder 8F
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15. getItemViewType
16. getItemViewType %FQFOEJOH
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17. Let’s see the overview.
18. RecyclerView.Adapter Overview @Override public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) { int viewType = getItemViewType(position);
 switch (viewType) { case R.layout.row_taro:
 onBindTaroViewHolder((TaroViewHolder) holder, position); break; case R.layout.row_shiro:
 onBindShiroViewHolder((ShiroViewHolder) holder, position); break; case R.layout.row_leona: onBindLeonaViewHolder((LeonaViewHolder) holder, position); break;
 default:
 throw new IllegalArgumentException(“Some message.”);
 } } @Override public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { LayoutInflater inflater = LayoutInflater.from(parent.getContext()); switch (viewType) { case R.layout.row_taro:
 View taroView = inflater.inflate(R.layout.row_taro, parent, false);
 return new TaroViewHolder(taroView);
 case R.layout.row_shiro:
 View shiroView = inflater.inflate(R.layout.row_shiro, parent, false);
 return new ShiroViewHolder(shiroView);
 case R.layout.row_leona:
 View leonaView = inflater.inflate(R.layout.row_leona, parent, false);
 return new LeonaViewHolder(leonaView);
 default:
 throw new IllegalArgumentException(“error message here.”);
 }
 }
19. RecyclerView.Adapter Overview @Override public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) { int viewType = getItemViewType(position);
 switch (viewType) { case R.layout.row_taro:
 onBindTaroViewHolder((TaroViewHolder) holder, position); break; case R.layout.row_shiro:
 onBindShiroViewHolder((ShiroViewHolder) holder, position); break; case R.layout.row_leona: onBindLeonaViewHolder((LeonaViewHolder) holder, position); break;
 default:
 throw new IllegalArgumentException(“Some message.”);
 } } @Override public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { LayoutInflater inflater = LayoutInflater.from(parent.getContext()); switch (viewType) { case R.layout.row_taro:
 View taroView = inflater.inflate(R.layout.row_taro, parent, false);
 return new TaroViewHolder(taroView);
 case R.layout.row_shiro:
 View shiroView = inflater.inflate(R.layout.row_shiro, parent, false);
 return new ShiroViewHolder(shiroView);
 case R.layout.row_leona:
 View leonaView = inflater.inflate(R.layout.row_leona, parent, false);
 return new LeonaViewHolder(leonaView);
 default:
 throw new IllegalArgumentException(“error message here.”);
 }
 }
20. RecyclerView.Adapter Overview @Override public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) { int viewType = getItemViewType(position);
 switch (viewType) { case R.layout.row_taro:
 onBindTaroViewHolder((TaroViewHolder) holder, position); break; case R.layout.row_shiro:
 onBindShiroViewHolder((ShiroViewHolder) holder, position); break; case R.layout.row_leona: onBindLeonaViewHolder((LeonaViewHolder) holder, position); break;
 default:
 throw new IllegalArgumentException(“Some message.”);
 } } @Override public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { LayoutInflater inflater = LayoutInflater.from(parent.getContext()); switch (viewType) { case R.layout.row_taro:
 View taroView = inflater.inflate(R.layout.row_taro, parent, false);
 return new TaroViewHolder(taroView);
 case R.layout.row_shiro:
 View shiroView = inflater.inflate(R.layout.row_shiro, parent, false);
 return new ShiroViewHolder(shiroView);
 case R.layout.row_leona:
 View leonaView = inflater.inflate(R.layout.row_leona, parent, false);
 return new LeonaViewHolder(leonaView);
 default:
 throw new IllegalArgumentException(“error message here.”);
 }
 } #PJMFSQMBUFTʜ
    
21. RecyclerView Boilerplates void onBindViewHolder(VH holder, int position) VH onCreateViewHolder(ViewGroup parent, int viewType) ɾ*OTUBOUJBUF
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22. YES WE WANT TO ELIMINATE THEM.
23. LET’S GENERATE THEM INSTEAD OF WRITING THEM.
24. PREREQUISITES
25. 1. Implement getItemViewType
26. @Override public int getItemViewType(int position) {
 switch (CatType.of(position)) {
 case TARO:
 return R.layout.row_taro;
 case SHIRO:
 return R.layout.row_shiro;
 case LEONA:
 return R.layout.row_leona;
 default:
 throw new IllegalArgumentException(“Some message.”);
 }
 } Implement RecyclerView.Adapter#getItemViewType()
27. @Override public int getItemViewType(int position) {
 switch (CatType.of(position)) {
 case TARO:
 return R.layout.row_taro;
 case SHIRO:
 return R.layout.row_shiro;
 case LEONA:
 return R.layout.row_leona;
 default:
 throw new IllegalArgumentException(“Some message.”);
 }
 } Implement RecyclerView.Adapter#getItemViewType() Return R.layout.id as view type
28. 2. Add annotations @AdapterBinding @ViewHolder @OnBind
29. @AdapterBinding public class CatAdapter extends RecyclerView.Adapter { … } @ViewHolder(layout = R.layout.row_title) static class TitleViewHolder extends RecyclerView.ViewHolder {
 TitleViewHolder(View itemView) {
 super(itemView);
 } 
 
 @OnBind void onBind() {
 // bind layouts
 }
 … Add @AdapterBinding ,@ViewHolder, @OnBind (optional) annotations
30. @AdapterBinding public class CatAdapter extends RecyclerView.Adapter { … } @ViewHolder(layout = R.layout.row_title) static class TitleViewHolder extends RecyclerView.ViewHolder {
 TitleViewHolder(View itemView) {
 super(itemView);
 } 
 
 @OnBind void onBind() {
 // bind layouts
 }
 … Add @AdapterBinding ,@ViewHolder, @OnBind (optional) annotations Add on RecyclerView.Adapter Add on RecyclerView.ViewHolder Add on inner methods within RecyclerView.ViewHolder
31. 3. Rebuild Project
32. 4. Call generated methods
33. Call static methods within generated class @Override public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) { CatAdapterViewHolderBinding.bindViewHolder(this, holder, position); } @Override public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { LayoutInflater inflater = LayoutInflater.from(parent.getContext()); return CatAdapterViewHolderBinding.createViewHolder(inflater, parent, viewType); }
34. Call static methods within generated class @Override public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) { CatAdapterViewHolderBinding.bindViewHolder(this, holder, position); } @Override public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { LayoutInflater inflater = LayoutInflater.from(parent.getContext()); return CatAdapterViewHolderBinding.createViewHolder(inflater, parent, viewType); } Adapter໊ʴViewHolderBinding.bindViewHolder Adapter໊ʴViewHolderBinding.bindViewHolder.createViewHolder
35. Let’s take a look at generated source codes.
36. class CatAdapterViewHolderBinding { public static ViewHolder createViewHolder(LayoutInflater inflater, ViewGroup parent, int viewType) { switch (viewType) { case 2130968636: View TaroViewHolderView = inflater.inflate(2130968636, parent, false); return new CatAdapter.TaroViewHolder(TaroViewHolderView); case 2130968635: View ShiroViewHolderView = inflater.inflate(2130968635, parent, false); return new CatAdapter.ShiroViewHolder(ShiroViewHolderView); case 2130968634: View LeonaViewHolderView = inflater.inflate(2130968634, parent, false); return new CatAdapter.LeonaViewHolder(LeonaViewHolderView); case 2130968637: View TitleViewHolderView = inflater.inflate(2130968637, parent, false); return new CatAdapter.TitleViewHolder(TitleViewHolderView); default: throw new IllegalArgumentException(String.format(Locale.US, "Illegal viewType(%d) passed to CatAdapter.", viewType)); } } Generated method: createViewHolder
37. Generated method: bindViewHolder public static void bindViewHolder(Adapter adapter, ViewHolder holder, int position) { int viewType = adapter.getItemViewType(position); switch (viewType) { case 2130968636: ((CatAdapter.TaroViewHolder) holder).onBind(); break; case 2130968635: ((CatAdapter.ShiroViewHolder) holder).onBind(); break; case 2130968634: ((CatAdapter.LeonaViewHolder) holder).onBind(position); break; case 2130968637: ((CatAdapter.TitleViewHolder) holder).onBind(); break; default: throw new IllegalArgumentException(String.format(Locale.US, "Illegal viewType(%d) passed to CatAdapter.", viewType)); } } }
38. ViewHolderBinding IUUQTHJUIVCDPNTIBVOLBXBOP7JFX)PMEFS#JOEJOH
39. Conclusion
40. ɾGenerating codes using Annotation Processor is fun! ɾWe’ll keep using RecyclerView for sure, so ɾLet us write less to do more! ·ͱΊ
41. THANK YOU ! ΁͍΁͍ @shaunkawano גࣜձࣾτϧς / Android Developer