PlaylistCursorAdapter.java

/**
 * 
 */
package gilday.android.powerhour.view;

import gilday.android.powerhour.R;
import gilday.android.powerhour.data.PowerHour.NowPlaying;
import gilday.android.powerhour.data.PreferenceRepository;
import android.content.Context;
import android.database.Cursor;
import android.support.v4.widget.CursorAdapter;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import android.widget.ToggleButton;

/**
 * Cursor adapter which binds a Cursor for the Power Hour database to the playlist 
 * edit list. Exposes an event which signifies when the user wishes to toggle the 
 * omission property for a song item in the playlist
 * @author jgilday
 *
 */
public class PlaylistCursorAdapter extends CursorAdapter {
	
	private SongOmitHandler listener;
	private boolean isShuffle;
	
	/**
	 * Holds the single instance of the OmitButtonHandler. Re-using 
	 * the same OmitToggleHandler instance saves on performance.
	 */
	private OmitButtonHandler internalButtonHandler;
	
	public PlaylistCursorAdapter(Context context, Cursor cursor, int flags) 
	{
		super(context, cursor, flags);
		internalButtonHandler = new OmitButtonHandler();
		isShuffle = new PreferenceRepository(context).isShuffle();
	}

	@Override
	public void bindView(View view, Context context, Cursor cursor) {
		ViewHolder vh = (ViewHolder) view.getTag();
		bindViewHolder(vh, cursor);
	}

	@Override
	public View newView(Context context, final Cursor cursor, ViewGroup parent) {
		// Inflate the views
		final LayoutInflater inflater = LayoutInflater.from(context);
		final View view = inflater.inflate(R.layout.song_item, parent, false);
		// Create a viewholder to hold references to the views 
		ViewHolder vh = new ViewHolder();
		vh.positionView = (TextView)view.findViewById(R.id.songitem_position);
		vh.artistView = (TextView)view.findViewById(R.id.songitem_artist);
		vh.titleView = (TextView)view.findViewById(R.id.songitem_name);
		vh.omitToggleButton = (ToggleButton)view.findViewById(R.id.songitem_omit);
		view.setTag(vh);
		// Use helper function to bind cursor data to the views
		bindViewHolder(vh, cursor);
		// Clear out listeners in case they're still hanging around
		vh.omitToggleButton.setOnClickListener(null);
		// Register this listener
		vh.omitToggleButton.setOnClickListener(internalButtonHandler);
		return view;
	}
	
	public void setOmitToggleListener(SongOmitHandler listener) {
		this.listener = listener;
	}
	
	private void bindViewHolder(ViewHolder vh, Cursor cursor) {
		int position = isShuffle ? 
				cursor.getInt(cursor.getColumnIndex(NowPlaying.SHUFFLE_POSITION)) : 
				cursor.getInt(cursor.getColumnIndex(NowPlaying.POSITION));
		vh.positionView.setText(String.valueOf(position));
		vh.artistView.setText(cursor.getString(cursor.getColumnIndex(NowPlaying.ARTIST)));
		vh.titleView.setText(cursor.getString(cursor.getColumnIndex(NowPlaying.TITLE)));
		int omit = cursor.getInt(cursor.getColumnIndex(NowPlaying.OMIT));
		// Put the song ID and isChecked in the toggle button's Tag reference
		// The song ID will help the onCheckedChanged event snag the song ID that it is relevant to
		vh.omitToggleButton.setTag(cursor.getInt(cursor.getColumnIndex(NowPlaying._ID)));
		vh.omitToggleButton.setChecked(omit <= 0);
		
		boolean enableSongItem = cursor.getInt(cursor.getColumnIndex(NowPlaying.PLAYED)) <= 0;
		vh.artistView.setEnabled(enableSongItem);
		vh.positionView.setEnabled(enableSongItem);
		vh.titleView.setEnabled(enableSongItem);
		vh.omitToggleButton.setEnabled(enableSongItem);
	}
	
	/**
	 * The PlaylistCursorAdapter fires an event when a song is omitted from or marked for 
	 * re-inclusion in the now playing playlist. 
	 * @author jgilday
	 *
	 */
	public interface SongOmitHandler
	{
		void onSongOmissionChanged(int songId, boolean isOmitted);
	}
	
	/**
	 * Using this private class to catch the CompoundButton.OnClick 
	 * to handle this View based event internally and without having to expose a 
	 * public CompoundButton.OnCheckedChangeListener on PlaylistCursorAdapter
	 * Better encapsulation of UI
	 * Need to catch onClick instead of onCheckedChanged because the ContentProvider's interaction 
	 * with this CursorAdapter causes an infinite loop of onCheckedChanged and it chokes the main 
	 * thread
	 * @author jgilday
	 *
	 */
	private class OmitButtonHandler implements View.OnClickListener
	{

		public void onClick(View v) {
			// Forward this event on to a the OmitToggleListener in a way that 
			// keeps all the View stuff encapsulated here
			if(listener != null) {
				boolean isChecked = ((ToggleButton)v).isChecked();
				int songId = (Integer) v.getTag();
				listener.onSongOmissionChanged(songId, !isChecked);
			}
		}
	}
	
	/**
	 * View Holder Android pattern. Caches pointers to Views that make up each list 
	 * item view
	 * @author jgilday
	 *
	 */
	private class ViewHolder
	{
		public TextView positionView;
		public TextView artistView;
		public TextView titleView;
		public ToggleButton omitToggleButton;
	}
}