package com.malmstein.yahnac.views.recyclerview.adapter;
import android.database.ContentObserver;
import android.database.Cursor;
import android.database.DataSetObserver;
import android.os.Handler;
import android.support.v7.widget.RecyclerView;
import android.widget.Filter;
import android.widget.FilterQueryProvider;
import android.widget.Filterable;
/**
* Provide a {@link android.support.v7.widget.RecyclerView.Adapter} implementation with cursor
* support.
* <p/>
* Child classes only need to implement {@link #onCreateViewHolder(android.view.ViewGroup, int)} and
* {@link #onBindViewHolderCursor(android.support.v7.widget.RecyclerView.ViewHolder, android.database.Cursor)}.
* <p/>
* This class does not implement deprecated fields and methods from CursorAdapter! Incidentally,
* only {@link android.widget.CursorAdapter#FLAG_REGISTER_CONTENT_OBSERVER} is available, so the
* flag is implied, and only the Adapter behavior using this flag has been ported.
*
* @param <VH> {@inheritDoc}
* @see android.support.v7.widget.RecyclerView.Adapter
* @see android.widget.CursorAdapter
* @see android.widget.Filterable
*/
public abstract class CursorRecyclerAdapter<VH extends android.support.v7.widget.RecyclerView.ViewHolder> extends RecyclerView.Adapter<VH>
implements Filterable, CursorFilter.CursorFilterClient {
private boolean mDataValid;
private int mRowIDColumn;
private Cursor mCursor;
private ChangeObserver mChangeObserver;
private DataSetObserver mDataSetObserver;
private CursorFilter mCursorFilter;
private FilterQueryProvider mFilterQueryProvider;
public CursorRecyclerAdapter(Cursor cursor) {
init(cursor);
}
void init(Cursor c) {
boolean cursorPresent = c != null;
mCursor = c;
mDataValid = cursorPresent;
mRowIDColumn = cursorPresent ? c.getColumnIndexOrThrow("_id") : -1;
mChangeObserver = new ChangeObserver();
mDataSetObserver = new MyDataSetObserver();
if (cursorPresent) {
if (mChangeObserver != null) {
c.registerContentObserver(mChangeObserver);
}
if (mDataSetObserver != null) {
c.registerDataSetObserver(mDataSetObserver);
}
}
}
/**
* This method will move the Cursor to the correct position and call
* {@link #onBindViewHolderCursor(android.support.v7.widget.RecyclerView.ViewHolder,
* android.database.Cursor)}.
*
* @param holder {@inheritDoc}
* @param i {@inheritDoc}
*/
@Override
public void onBindViewHolder(VH holder, int i) {
if (!mDataValid) {
throw new IllegalStateException("this should only be called when the cursor is valid");
}
if (!mCursor.moveToPosition(i)) {
throw new IllegalStateException("couldn't move cursor to position " + i);
}
onBindViewHolderCursor(holder, mCursor);
}
/**
* See {@link android.widget.CursorAdapter#bindView(android.view.View, android.content.Context,
* android.database.Cursor)},
* {@link #onBindViewHolder(android.support.v7.widget.RecyclerView.ViewHolder, int)}
*
* @param holder View holder.
* @param cursor The cursor from which to get the data. The cursor is already
* moved to the correct position.
*/
public abstract void onBindViewHolderCursor(VH holder, Cursor cursor);
@Override
public int getItemCount() {
if (mDataValid && mCursor != null) {
return mCursor.getCount();
} else {
return 0;
}
}
/**
* @see android.widget.ListAdapter#getItemId(int)
*/
@Override
public long getItemId(int position) {
if (mDataValid && mCursor != null) {
if (mCursor.moveToPosition(position)) {
return mCursor.getLong(mRowIDColumn);
} else {
return 0;
}
} else {
return 0;
}
}
public Cursor getCursor() {
return mCursor;
}
/**
* Change the underlying cursor to a new cursor. If there is an existing cursor it will be
* closed.
*
* @param cursor The new cursor to be used
*/
public void changeCursor(Cursor cursor) {
Cursor old = swapCursor(cursor);
if (old != null) {
old.close();
}
}
/**
* Swap in a new Cursor, returning the old Cursor. Unlike
* {@link #changeCursor(Cursor)}, the returned old Cursor is <em>not</em>
* closed.
*
* @param newCursor The new cursor to be used.
* @return Returns the previously set Cursor, or null if there wasa not one.
* If the given new Cursor is the same instance is the previously set
* Cursor, null is also returned.
*/
public Cursor swapCursor(Cursor newCursor) {
if (newCursor == mCursor) {
return null;
}
Cursor oldCursor = mCursor;
if (oldCursor != null) {
if (mChangeObserver != null) {
oldCursor.unregisterContentObserver(mChangeObserver);
}
if (mDataSetObserver != null) {
oldCursor.unregisterDataSetObserver(mDataSetObserver);
}
}
mCursor = newCursor;
if (newCursor != null) {
if (mChangeObserver != null) {
newCursor.registerContentObserver(mChangeObserver);
}
if (mDataSetObserver != null) {
newCursor.registerDataSetObserver(mDataSetObserver);
}
mRowIDColumn = newCursor.getColumnIndexOrThrow("_id");
mDataValid = true;
// notify the observers about the new cursor
notifyDataSetChanged();
} else {
mRowIDColumn = -1;
mDataValid = false;
// notify the observers about the lack of a data set
// notifyDataSetInvalidated();
notifyItemRangeRemoved(0, getItemCount());
}
return oldCursor;
}
/**
* <p>Converts the cursor into a CharSequence. Subclasses should override this
* method to convert their results. The default implementation returns an
* empty String for null values or the default String representation of
* the value.</p>
*
* @param cursor the cursor to convert to a CharSequence
* @return a CharSequence representing the value
*/
public CharSequence convertToString(Cursor cursor) {
return cursor == null ? "" : cursor.toString();
}
/**
* Runs a query with the specified constraint. This query is requested
* by the filter attached to this adapter.
* <p/>
* The query is provided by a
* {@link android.widget.FilterQueryProvider}.
* If no provider is specified, the current cursor is not filtered and returned.
* <p/>
* After this method returns the resulting cursor is passed to {@link #changeCursor(Cursor)}
* and the previous cursor is closed.
* <p/>
* This method is always executed on a background thread, not on the
* application's main thread (or UI thread.)
* <p/>
* Contract: when constraint is null or empty, the original results,
* prior to any filtering, must be returned.
*
* @param constraint the constraint with which the query must be filtered
* @return a Cursor representing the results of the new query
* @see #getFilter()
* @see #getFilterQueryProvider()
* @see #setFilterQueryProvider(android.widget.FilterQueryProvider)
*/
public Cursor runQueryOnBackgroundThread(CharSequence constraint) {
if (mFilterQueryProvider != null) {
return mFilterQueryProvider.runQuery(constraint);
}
return mCursor;
}
public Filter getFilter() {
if (mCursorFilter == null) {
mCursorFilter = new CursorFilter(this);
}
return mCursorFilter;
}
/**
* Returns the query filter provider used for filtering. When the
* provider is null, no filtering occurs.
*
* @return the current filter query provider or null if it does not exist
* @see #setFilterQueryProvider(android.widget.FilterQueryProvider)
* @see #runQueryOnBackgroundThread(CharSequence)
*/
public FilterQueryProvider getFilterQueryProvider() {
return mFilterQueryProvider;
}
/**
* Sets the query filter provider used to filter the current Cursor.
* The provider's
* {@link android.widget.FilterQueryProvider#runQuery(CharSequence)}
* method is invoked when filtering is requested by a client of
* this adapter.
*
* @param filterQueryProvider the filter query provider or null to remove it
* @see #getFilterQueryProvider()
* @see #runQueryOnBackgroundThread(CharSequence)
*/
public void setFilterQueryProvider(FilterQueryProvider filterQueryProvider) {
mFilterQueryProvider = filterQueryProvider;
}
/**
* Called when the {@link ContentObserver} on the cursor receives a change notification.
* Can be implemented by sub-class.
*
* @see ContentObserver#onChange(boolean)
*/
protected void onContentChanged() {
}
private class ChangeObserver extends ContentObserver {
public ChangeObserver() {
super(new Handler());
}
@Override
public boolean deliverSelfNotifications() {
return true;
}
@Override
public void onChange(boolean selfChange) {
onContentChanged();
}
}
private class MyDataSetObserver extends DataSetObserver {
@Override
public void onChanged() {
mDataValid = true;
notifyDataSetChanged();
}
@Override
public void onInvalidated() {
mDataValid = false;
// notifyDataSetInvalidated();
notifyItemRangeRemoved(0, getItemCount());
}
}
/**
* <p>The CursorFilter delegates most of the work to the CursorAdapter.
* Subclasses should override these delegate methods to run the queries
* and convert the results into String that can be used by auto-completion
* widgets.</p>
*/
}
class CursorFilter extends Filter {
CursorFilterClient mClient;
CursorFilter(CursorFilterClient client) {
mClient = client;
}
@Override
public CharSequence convertResultToString(Object resultValue) {
return mClient.convertToString((Cursor) resultValue);
}
@Override
protected FilterResults performFiltering(CharSequence constraint) {
Cursor cursor = mClient.runQueryOnBackgroundThread(constraint);
FilterResults results = new FilterResults();
if (cursor != null) {
results.count = cursor.getCount();
results.values = cursor;
} else {
results.count = 0;
results.values = null;
}
return results;
}
@Override
protected void publishResults(CharSequence constraint, FilterResults results) {
Cursor oldCursor = mClient.getCursor();
if (results.values != null && results.values != oldCursor) {
mClient.changeCursor((Cursor) results.values);
}
}
interface CursorFilterClient {
CharSequence convertToString(Cursor cursor);
Cursor runQueryOnBackgroundThread(CharSequence constraint);
Cursor getCursor();
void changeCursor(Cursor cursor);
}
}