package com.cardinalsolutions.sectioned_adapter;
import android.content.Context;
import android.graphics.Color;
import android.support.annotation.IntDef;
import android.support.annotation.LayoutRes;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.LinearLayout;
import android.widget.TextView;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
/**
* A {@link RecyclerView.Adapter} that is capable of automatically generating section header views
* and inserting them into a list of {@link Categorizable} data.
* <p/>
* <p>
* Subclasses should implement <code>onCreateItemViewHolder()</code> to return a
* {@link android.support.v7.widget.RecyclerView.ViewHolder} for their data object and then
* implement <code>onBindItemViewHolder()</code> to bind the data object to the view.
* </p>
* <p>
* Calling <code>setItemList()</code> with a list of <code>Categorizable</code> objects will
* automatically generate and insert headers at the appropriate positions. The list of items
* does not need to be sorted.
* </p>
*
* @author Alex Morgan {[email protected]}
*/
public abstract class SectionedAdapter<T extends Categorizable> extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
@IntDef({TYPE_ITEM, TYPE_SECTION_HEADER})
@Retention(RetentionPolicy.SOURCE)
public @interface ViewType {
}
private static final int TYPE_ITEM = 0;
private static final int TYPE_SECTION_HEADER = 1;
private List<Object> itemList;
@LayoutRes
private int headerLayoutResource = -1;
@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
switch (this.getItemViewType(position)) {
case TYPE_SECTION_HEADER: {
SectionHeader header = (SectionHeader) this.itemList.get(position);
((SectionViewHolder) holder).titleView.setText(header.title);
break;
}
case TYPE_ITEM: {
this.onBindItemViewHolder(holder, (T) this.itemList.get(position), this.getItemViewType(position));
break;
}
default: {
throw new RuntimeException("SectionedAdapter could not bind the requested view type.");
}
}
}
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, @ViewType int viewType) {
switch (viewType) {
case TYPE_SECTION_HEADER: {
View view;
if (this.headerLayoutResource == -1) {
view = this.createStandardHeaderView(parent);
} else {
view = this.createCustomHeaderView(parent, this.headerLayoutResource);
}
return new SectionViewHolder(view);
}
case TYPE_ITEM: {
return this.onCreateItemViewHolder(parent, viewType);
}
default: {
throw new RuntimeException("SectionedAdapter could not create a ViewHolder for the requested view type.");
}
}
}
@Override
@ViewType
public int getItemViewType(int position) {
if (itemList.get(position) instanceof Categorizable) {
return TYPE_ITEM;
} else if (itemList.get(position) instanceof SectionHeader) {
return TYPE_SECTION_HEADER;
} else {
throw new RuntimeException("SectionedAdapter was unable to determine the view type for the item at position " + position);
}
}
@Override
public int getItemCount() {
return itemList.size();
}
/**
* Sets the list of items to be displayed in the adapter. This method automatically takes care
* of sorting the data according to category and inserts header views at the beginning of each
* category.
*
* @param itemList a list of {@link Categorizable} objects to be displayed in sections
*/
public void setItemList(List<? extends Categorizable> itemList) {
Collections.sort(itemList, new Comparator<Categorizable>() {
@Override
public int compare(Categorizable lhs, Categorizable rhs) {
return String.CASE_INSENSITIVE_ORDER.compare(lhs.getCategory(), rhs.getCategory());
}
});
this.itemList = SectionGenerator.getSectionsForItems(itemList);
this.notifyDataSetChanged();
}
/**
* Sets a layout resource to inflate when creating the headers for sections. The specified
* layout must contain a TextView with the id <code>android.R.id.title</code> or else an
* exception will be thrown when the ViewHolder is later bound.
*
* @param headerResource the resource ID
*/
protected void setCustomHeaderLayout(@LayoutRes int headerResource) {
this.headerLayoutResource = headerResource;
}
/**
* This method is called when the adapter needs to bind data for a data object into a view holder.
*
* @param holder a {@link android.support.v7.widget.RecyclerView.ViewHolder} subclass of the
* same type supplied by <code>onCreateItemViewHolder()</code>
* @param item the data object to bind
* @param viewType the type of view that should be bound
*/
public abstract void onBindItemViewHolder(RecyclerView.ViewHolder holder, T item, @ViewType int viewType);
/**
* This method is called to create a {@link android.support.v7.widget.RecyclerView.ViewHolder}
* for each item in the adapter. It should return a ViewHolder subclass suitable for binding
* to the specified view type.
*
* @param parent The ViewGroup into which the new View will be added after it is bound to an adapter position.
* @param viewType The type of the new View
* @return A new ViewHolder that holds a View of the given view type.
*/
public abstract RecyclerView.ViewHolder onCreateItemViewHolder(ViewGroup parent, @ViewType int viewType);
/**
* A ViewHolder for holding a section header's View.
*/
private static class SectionViewHolder extends RecyclerView.ViewHolder {
private final TextView titleView;
SectionViewHolder(View itemView) {
super(itemView);
this.titleView = (TextView) itemView.findViewWithTag("TITLE");
}
}
static class SectionHeader {
SectionHeader(String title) {
this.title = title;
}
final String title;
}
private View createStandardHeaderView(View parent) {
LinearLayout sectionView = new LinearLayout(parent.getContext());
sectionView.setLayoutParams(parent.getLayoutParams());
int horizontalPadding = this.pixelsToDp(parent.getContext(), 16);
int verticalPadding = this.pixelsToDp(parent.getContext(), 8);
sectionView.setPadding(horizontalPadding, verticalPadding, horizontalPadding, verticalPadding);
TextView titleView = new TextView(parent.getContext());
titleView.setTag("TITLE");
titleView.setTextColor(Color.BLACK);
sectionView.addView(titleView);
return sectionView;
}
private View createCustomHeaderView(ViewGroup parent, @LayoutRes int layoutResource) {
View view = LayoutInflater.from(parent.getContext()).inflate(layoutResource, parent, false);
TextView titleView = (TextView) view.findViewById(android.R.id.title);
if (titleView == null) {
throw new RuntimeException("The header layout file MUST contain a TextView with the id `android.R.id.title`; unable to bind header views.");
}
titleView.setTag("TITLE");
return view;
}
private int pixelsToDp(Context context, int pixels) {
float scale = context.getResources().getDisplayMetrics().density;
return (int) (pixels * scale + 0.5f);
}
}
