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Desenvolvedora Android
Criando uma lista heterogênea com recyclerview e
viewtypes
Paula Rosa
RecyclerView
RecyclerView
LayoutManager Adapter Dados
• Somente a RecyclerView atualiza o adapter.
• O LayoutManager cuida de calcular o layout para
saber quantos itens caberão a cada scroll
• Quando a lista sofre um scroll, a RecyclerView avisa
o LayoutManager e ele escrola a lista.
• Aumenta consideravelmente a performance da lista,
pois pode alterar somente uma parte (range) da lista
• Animações mais fáceis de codificar;
Lista Heterogêna
• Quando se precisa inflar mais de um tipo de layout, e que tenham formato de lista
• Quando uma lista precisa de header
• Quando precisar de muita performance
Quando usar?
ViewTypes
• É uma forma do android entender que há vários tipos de views na
recyclerview
• Sendo assim, se cria um ViewHolder para cada tipo de View (ViewType)
• O bind das views é feito baseado também no ViewType
Exemplo
ContactList
Categoria
Family Friends Work
if(!familyList.isEmpty()) {
recyclerData.add(null);
recyclerData.addAll(familyList);
} else if(!friendsList.isEmpty()) {
recyclerData.add(null);
recyclerData.addAll(friendsList);
}
private List<Contact> recyclerData = new ArrayList<>();
for(int i = 0; i < contactList.size(); i++) {
if(contactList.get(i).getCategory() == Contact.Category.FAMILY) {
familyList.add(contactList.get(i));
} else if(….) {
//TODO
}
Separa Listas
Cria uma lista de dados
getItemCount() —> return int
Tipos diferentes
de views
• Retorna tamanho total da lista
(itens da lista + headers)
• Ou retorna o tamanho da lista de
dados (recyclerData)
@Override
public int getItemCount() {
return recyclerData.size();
}
getItemViewType(int position) —> return
int
• Retorna o viewType desejado
para determinada posição
@Override
public int getItemViewType(int position) {
if (position == 0) {
return VIEW_TYPE_CATEGORY;
} else if (position == familyList.size() +1) {
return VIEW_TYPE_CATEGORY;
} else if (…){
(…)
}
}
@Override
public int getItemViewType(int position) {
if (recyclerData.get(position) == null) {
return VIEW_TYPE_CATEGORY;
} else {
return VIEW_TYPE_CONTACT_LIST;
}
}
ViewHolder
• Cria ViewHolder para cada tipo de View
static class ViewHolderContactList extends BaseViewHolder {
TexView contactName;
public ViewHolderContactList(View view) {
super(view);
contactName = (TextView) view.findViewById(R.id.name);
(…)
}
}
BaseViewHolder -> Classe Abstrata que herda de RecyclerView.ViewHolder
onCreateViewHolder(ViewGroup parent, int viewType) —> return BaseViewHolder
• Retorna o viewType desejado para determinada posição
@Override
public BaseViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
RecyclerView.ViewHolder viewHolder;
if (viewType == VIEW_TYPE_CATEGORY) {
View view = LayoutInflater.from(parent.getContext())
.inflate(R.layout.view_header_category, parent, false);
viewHolder = new ViewHolderCategory(view);
} else {
View view = LayoutInflater.from(parent.getContext())
.inflate(R.layout.view_item_contact, parent, false);
viewHolder = new ViewHolderContactList(view);
}
}
onBindViewHolder(BaseViewHolder parent, int position) —> return int
• Seta os valores de cada view em determinada posição
@Override
public void onBindViewHolder(BaseViewHolder parent, int position) {
BaseViewHolder viewHolder;
if (getItemViewType(position) == VIEW_TYPE_CATEGORY) {
ViewHolderCategory viewHolderCategory = (ViewHolderCategory) holder;
(…)
viewHolderCategory.categoryName.setText(categoria);
} else {
ViewHolderContactList viewHolderContact = (ViewHolderContactList) holder;
(…)
viewHolderContact.contactName.setText(recyclerData.get(position).getName);
}
}
finaly {}
• https://github.com/paulacr/ViewTypesRecyclerView
• https://guides.codepath.com/android/Heterogenous-Layouts-inside-
RecyclerView

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Recyclerview view types

  • 1. Desenvolvedora Android Criando uma lista heterogênea com recyclerview e viewtypes Paula Rosa
  • 2. RecyclerView RecyclerView LayoutManager Adapter Dados • Somente a RecyclerView atualiza o adapter. • O LayoutManager cuida de calcular o layout para saber quantos itens caberão a cada scroll • Quando a lista sofre um scroll, a RecyclerView avisa o LayoutManager e ele escrola a lista. • Aumenta consideravelmente a performance da lista, pois pode alterar somente uma parte (range) da lista • Animações mais fáceis de codificar;
  • 3. Lista Heterogêna • Quando se precisa inflar mais de um tipo de layout, e que tenham formato de lista • Quando uma lista precisa de header • Quando precisar de muita performance Quando usar?
  • 4. ViewTypes • É uma forma do android entender que há vários tipos de views na recyclerview • Sendo assim, se cria um ViewHolder para cada tipo de View (ViewType) • O bind das views é feito baseado também no ViewType
  • 6. if(!familyList.isEmpty()) { recyclerData.add(null); recyclerData.addAll(familyList); } else if(!friendsList.isEmpty()) { recyclerData.add(null); recyclerData.addAll(friendsList); } private List<Contact> recyclerData = new ArrayList<>(); for(int i = 0; i < contactList.size(); i++) { if(contactList.get(i).getCategory() == Contact.Category.FAMILY) { familyList.add(contactList.get(i)); } else if(….) { //TODO } Separa Listas Cria uma lista de dados
  • 7. getItemCount() —> return int Tipos diferentes de views • Retorna tamanho total da lista (itens da lista + headers) • Ou retorna o tamanho da lista de dados (recyclerData) @Override public int getItemCount() { return recyclerData.size(); }
  • 8. getItemViewType(int position) —> return int • Retorna o viewType desejado para determinada posição @Override public int getItemViewType(int position) { if (position == 0) { return VIEW_TYPE_CATEGORY; } else if (position == familyList.size() +1) { return VIEW_TYPE_CATEGORY; } else if (…){ (…) } } @Override public int getItemViewType(int position) { if (recyclerData.get(position) == null) { return VIEW_TYPE_CATEGORY; } else { return VIEW_TYPE_CONTACT_LIST; } }
  • 9. ViewHolder • Cria ViewHolder para cada tipo de View static class ViewHolderContactList extends BaseViewHolder { TexView contactName; public ViewHolderContactList(View view) { super(view); contactName = (TextView) view.findViewById(R.id.name); (…) } } BaseViewHolder -> Classe Abstrata que herda de RecyclerView.ViewHolder
  • 10. onCreateViewHolder(ViewGroup parent, int viewType) —> return BaseViewHolder • Retorna o viewType desejado para determinada posição @Override public BaseViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { RecyclerView.ViewHolder viewHolder; if (viewType == VIEW_TYPE_CATEGORY) { View view = LayoutInflater.from(parent.getContext()) .inflate(R.layout.view_header_category, parent, false); viewHolder = new ViewHolderCategory(view); } else { View view = LayoutInflater.from(parent.getContext()) .inflate(R.layout.view_item_contact, parent, false); viewHolder = new ViewHolderContactList(view); } }
  • 11. onBindViewHolder(BaseViewHolder parent, int position) —> return int • Seta os valores de cada view em determinada posição @Override public void onBindViewHolder(BaseViewHolder parent, int position) { BaseViewHolder viewHolder; if (getItemViewType(position) == VIEW_TYPE_CATEGORY) { ViewHolderCategory viewHolderCategory = (ViewHolderCategory) holder; (…) viewHolderCategory.categoryName.setText(categoria); } else { ViewHolderContactList viewHolderContact = (ViewHolderContactList) holder; (…) viewHolderContact.contactName.setText(recyclerData.get(position).getName); } }
  • 12. finaly {} • https://github.com/paulacr/ViewTypesRecyclerView • https://guides.codepath.com/android/Heterogenous-Layouts-inside- RecyclerView