Android: Switch between Activties!
<p>I am trying to develop an audio player and I have a problem..</p>

<p>My first activity has a list of the mp3's from my sd card and I can choose some them and put them in an ArrayList.  I have a button (Add to playlist), and when I press it, it starts the new activity where I take the ArrayList, there I create my player, play music etc. But... when I press the back button on the device(you know this that look like such as a half-circled arrow), i go back to my first activity, but the music don't stop and I can choose again songs and if I press the Add To Playlist button then the app plays two songs simultaneously (my first and this second).</p>

<p>How can I handle this?  (I want when i go back, choose or unchoose some tracks and then when i press the button (Add to playlist) to play my new list) thanks...!!</p>

<p>I start my second activity like that:</p>

<pre><code>Intent intent = new Intent (Chooser.this, Player.class);
Bundle b = new Bundle();    
b.putStringArrayList("key", plist);     
b.putStringArrayList("pos", po);           
intent.putExtras(b);
startActivity(intent);  
</code></pre>

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<p>i don't want my player stops, simply i want to add or remove songs in my playlist....</p>
