BackgroundTask.java

/*******************************************************************************
 * Copyright (c) 2011 Michel DAVID mimah35-at-gmail.com
 * 
 * This program 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.
 * 
 * This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
 ******************************************************************************/
package fr.gotorennes.util;

import java.util.ArrayList;
import java.util.List;

import android.app.Activity;
import android.app.ProgressDialog;
import android.content.DialogInterface;
import android.content.DialogInterface.OnCancelListener;
import android.os.AsyncTask;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import fr.gotorennes.R;

public abstract class BackgroundTask<T> {

	private boolean showPopup;
	private String message;
	private AsyncTask<Void,String,T> task;
	private List<Handler> handlers = new ArrayList<Handler>();

	public BackgroundTask() {
		this(true);
	}

	public BackgroundTask(String message) {
		this(message, true);
	}

	public BackgroundTask(boolean showPopup) {
		this(null, showPopup);
	}

	public BackgroundTask(String message, boolean showPopup) {
		this.message = message;
		this.showPopup = showPopup;
	}

	public void addHandler(Handler handler) {
		handlers.add(handler);
	}
	
	protected abstract T execute();

	protected abstract void callback(T result);
	
	public void start(Activity context) {

		if(message == null) {
			message = context.getString(R.string.chargement);
		}
		
		final ProgressDialog waitDialog = showPopup ? ProgressDialog.show(context, context.getString(R.string.titre), message, true, true, new OnCancelListener() {
			
			@Override
			public void onCancel(DialogInterface dialog) {
				if(task != null){
					task.cancel(true);
				}
				task.cancel(true);
			}
		}) : null;
		
		task = new AsyncTask<Void, String, T>() {

			@Override
			protected T doInBackground(Void... params) {
				try {
					return BackgroundTask.this.execute();
				}
				catch(Throwable ex) {
					Log.e("GoToRennes", ex.getMessage(), ex);
				}
				return null;
			}

			@Override
			protected void onPostExecute(T result) {
				callback(result);
				if (waitDialog != null) {
					try {
						waitDialog.dismiss();
					}
					catch(Exception ex) {
						//Cas étrange sur certains tel
						// http://stackoverflow.com/questions/2745061/java-lang-illegalargumentexception-view-not-attached-to-window-manager
					}
				}
				
				for(Handler handler : handlers) {
					Message message = new Message();
					message.obj = result;
					handler.dispatchMessage(message);
				}
			}
		};
		task.execute();
	}
}