GenericModel.java

/**
 *  This file is part of ElasticDroid.
 *
 * ElasticDroid is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.

 * ElasticDroid is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.

 * You should have received a copy of the GNU General Public License
 * along with ElasticDroid.  If not, see <http://www.gnu.org/licenses/>.
 * 
 * Authored by Siddhu Warrier on 3 Nov 2010
 */
package org.elasticdroid.model.tpl;

import org.elasticdroid.R;
import org.elasticdroid.tpl.GenericActivity;
import org.elasticdroid.tpl.GenericListActivity;
import org.elasticdroid.utils.DialogConstants;

import android.app.Dialog;
import android.app.ProgressDialog;
import android.app.Service;
import android.os.AsyncTask;
import android.util.Log;

/**
 * Abstract class to add a few additional must-implement methods to AsyncTask.
 * 
 * This stays abstract so that I don't have to implement ASyncTask methods here.
 * @author Siddhu Warrier
 *
 * 3 Nov 2010
 */
public abstract class GenericModel<T,U,V> extends AsyncTask<T, U, V> {
	/** The activity to call */
	protected GenericActivity activity;
	/** The list activity to call */
	protected GenericListActivity listActivity;
	
	/** Boolean to indicate if listActivity is used instead*/
	protected boolean listActivityUsed;
	
	/**
	 * Constructor. Saves the activity that called this. This is used to return the data
	 * back to the (Generic)Activity.
	 * @param activity The Android UI activity that created the GenericModel.
	 */
	public GenericModel(GenericActivity activity) {
		this.activity = activity;
		this.listActivity = null; //redundant instruction. But ah well...
	}
	
	/**
	 * Another Constructor. This allows ListActivities to call GenericModel subtypes.
	 * The GenericListActivity subclass is called to return the data back to the View.
	 * 
	 * @param listActivity the Android UI ListActivity that created the GenericModel.
	 */
	public GenericModel(GenericListActivity listActivity) {
		this.listActivity = listActivity;
		this.activity = null; //redundant instruction. But ah well...
		this.listActivityUsed = true; //this will be used in onPreExecute and onPostExcecute()
	}
	
	/**
	 * Called in *UI Thread* before doInBackground executes in a separate thread.
	 */
	@Override
	protected void onPreExecute() {
		if (!listActivityUsed) {
			activity.showDialog(DialogConstants.PROGRESS_DIALOG.ordinal()); //the argument is not 
			//used
		}
		else {
			listActivity.showDialog(DialogConstants.PROGRESS_DIALOG.ordinal()); //the argument is 
			//not used
		}
	}
	
	/**
	 * Set the activity object referred to by the model. This is used
	 * by the activity to reset itself to null when it is being destroyed temporarily
	 * (for instance whenever the screen orientation is changed), and to
	 * reset it whenever the object is restored after being destroyed.
	 * @param activity the GenericActivity referred to in the Model 
	 */
	public void setActivity(GenericActivity activity) {
		this.activity = activity;
	}
	
	/**
	 * Overloaded method to set ListActivity.
	 * 
	 * Set the activity object referred to by the model. This is used
	 * by the activity to reset itself to null when it is being destroyed temporarily
	 * (for instance whenever the screen orientation is changed), and to
	 * reset it whenever the object is restored after being destroyed.
	 * @param listActivity the GenericListActivity referred to in the Model 
	 */
	public void setActivity(GenericListActivity listActivity) {
		this.listActivity = listActivity;
	}
	
	/**
	 * Method to set the activity to null. Called when activity is destroyed.
	 */
	public void setActivityNull() {
		if (listActivityUsed) {
			this.listActivity = null;
		}
		else {
			this.activity = null;
		}
	}
	
	/**
	 * Called in the *UI thread* after doInBackground completes.
	 * 
	 * @param result The results returned by doInBackground
	 */
	@Override
	protected void onPostExecute(Object result) {
		//just return the result produced to the Activity.
		//we could process it here, but I want to keep the MVC pattern clean.
		//Call me a f*cking pedant, if you will.
		//...
		//...
		//I HEARD THAT!!!
		if (!listActivityUsed) {
			if (activity != null) {
				activity.processModelResults(result);
			}
		}
		else { //if the activity that started this model is a GenericListActivity.
			if (listActivity != null) {
				listActivity.processModelResults(result);
			}
		}
	}
	
	/**
	 * Executed on the UI thread when the progress bar is cancelled.
	 * It returns null to the activity; the activity can process this if it likes.
	 */
	protected void onCancelled () {
		Log.v(this.getClass().getName(), "Cancelled!");
		//call the model results with a null
		//do not call processModelResults if the user has already reset the activity or
		//list activity to null. This can happen if hte user presses the back button in a
		//view that is executing a model in the background WITHOUT the progress dialog displaying.
		if (listActivityUsed) {
			if (listActivity != null) {
				listActivity.processModelResults(null);
			}
		}
		else {
			if (activity != null) {
				activity.processModelResults(null);
			}
		}
	}
}