PlaylistAdapter.java

package org.music.player;

import org.music.player.R;

import android.content.ContentResolver;
import android.content.ContentUris;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.graphics.drawable.Drawable;
import android.net.Uri;
import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import android.provider.MediaStore;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.CursorAdapter;
import android.widget.TextView;

/**
 * CursorAdapter backed by MediaStore playlists.
 */
public class PlaylistAdapter extends CursorAdapter implements Handler.Callback, DragListView.DragAdapter {
	private static final String[] PROJECTION = new String[] {
		MediaStore.Audio.Playlists.Members._ID,
		MediaStore.Audio.Playlists.Members.TITLE,
		MediaStore.Audio.Playlists.Members.ARTIST,
		MediaStore.Audio.Playlists.Members.AUDIO_ID,
		MediaStore.Audio.Playlists.Members.PLAY_ORDER,
	};

	private final Context mContext;
	private final Handler mWorkerHandler;
	private final Handler mUiHandler;
	private final LayoutInflater mInflater;
	private final Drawable mExpander;

	private long mPlaylistId;

	private boolean mEditable;

	/**
	 * Create a playlist adapter.
	 *
	 * @param context A context to use.
	 * @param worker A looper running a worker thread (to run queries on).
	 */
	public PlaylistAdapter(Context context, Looper worker)
	{
		super(context, null, false);

		mContext = context;
		mUiHandler = new Handler(this);
		mWorkerHandler = new Handler(worker, this);
		mInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
		mExpander = context.getResources().getDrawable(R.drawable.grabber);
	}

	/**
	 * Set the id of the backing playlist.
	 *
	 * @param id The MediaStore id of a playlist.
	 */
	public void setPlaylistId(long id)
	{
		mPlaylistId = id;
		mWorkerHandler.sendEmptyMessage(MSG_RUN_QUERY);
	}

	/**
	 * Enabled or disable edit mode. Edit mode adds a drag grabber to the left
	 * side a views and a delete button to the right side of views.
	 *
	 * @param editable True to enable edit mode.
	 */
	public void setEditable(boolean editable)
	{
		mEditable = editable;
		notifyDataSetInvalidated();
	}

	/**
	 * Update the values in the given view.
	 */
	@Override
	public void bindView(View view, Context context, Cursor cursor)
	{
		TextView textView = (TextView)view;
		textView.setText(cursor.getString(1));
		textView.setCompoundDrawablesWithIntrinsicBounds(mEditable ? mExpander : null, null, null, null);
		textView.setTag(cursor.getLong(3));
	}

	/**
	 * Generate a new view.
	 */
	@Override
	public View newView(Context context, Cursor cursor, ViewGroup parent)
	{
		return mInflater.inflate(R.layout.playlist_row, null);
	}

	/**
	 * Re-run the query. Should be run on worker thread.
	 */
	public static final int MSG_RUN_QUERY = 1;
	/**
	 * Update the cursor. Must be run on UI thread.
	 */
	public static final int MSG_UPDATE_CURSOR = 2;

	@Override
	public boolean handleMessage(Message message)
	{
		switch (message.what) {
		case MSG_RUN_QUERY: {
			Cursor cursor = runQuery(mContext.getContentResolver());
			mUiHandler.sendMessage(mUiHandler.obtainMessage(MSG_UPDATE_CURSOR, cursor));
			break;
		}
		case MSG_UPDATE_CURSOR:
			changeCursor((Cursor)message.obj);
			break;
		default:
			return false;
		}

		return true;
	}

	/**
	 * Query the playlist songs.
	 *
	 * @param resolver A ContentResolver to query with.
	 * @return The resulting cursor.
	 */
	private Cursor runQuery(ContentResolver resolver)
	{
		QueryTask query = MediaUtils.buildPlaylistQuery(mPlaylistId, PROJECTION, null);
		return query.runQuery(resolver);
	}

	@Override
	public void move(int from, int to)
	{
		if (from == to)
			// easy mode
			return;

		int count = getCount();
		if (to >= count || from >= count)
			// this can happen when the adapter changes during the drag
			return;

		// The Android API contains a method to move a playlist item, however,
		// it has only been available since Froyo and doesn't seem to work
		// after a song has been removed from the playlist (I think?).

		ContentResolver resolver = mContext.getContentResolver();
		Uri uri = MediaStore.Audio.Playlists.Members.getContentUri("external", mPlaylistId);
		Cursor cursor = getCursor();

		int start = Math.min(from, to);
		int end = Math.max(from, to);

		long order;
		if (start == 0) {
			order = 0;
		} else {
			cursor.moveToPosition(start - 1);
			order = cursor.getLong(4) + 1;
		}

		cursor.moveToPosition(end);
		long endOrder = cursor.getLong(4);

		// clear the rows we are replacing
		String[] args = new String[] { Long.toString(order), Long.toString(endOrder) };
		resolver.delete(uri, "play_order >= ? AND play_order <= ?", args);

		// create the new rows
		ContentValues[] values = new ContentValues[end - start + 1];
		for (int i = start, j = 0; i <= end; ++i, ++j, ++order) {
			cursor.moveToPosition(i == to ? from : i > to ? i - 1 : i + 1);
			ContentValues value = new ContentValues(2);
			value.put(MediaStore.Audio.Playlists.Members.PLAY_ORDER, Long.valueOf(order));
			value.put(MediaStore.Audio.Playlists.Members.AUDIO_ID, cursor.getLong(3));
			values[j] = value;
		}

		// insert the new rows
		resolver.bulkInsert(uri, values);

		changeCursor(runQuery(resolver));
	}

	@Override
	public void remove(int position)
	{
		ContentResolver resolver = mContext.getContentResolver();
		Uri uri = MediaStore.Audio.Playlists.Members.getContentUri("external", mPlaylistId);
		resolver.delete(ContentUris.withAppendedId(uri, getItemId(position)), null, null);
		changeCursor(runQuery(resolver));
	}
}