When to reset a callbackhandler for a Service
<p>i have two Activities A and B and one Service C. A starts B. </p>

<p>A and B: </p>

<ul>
<li>are binding and unbinding to the Service in <code>onStart()/onStop()</code>. </li>
<li>are implementing a <code>Handler</code>-Object that works with Messages. The Handler is needed, so if C is doing Work and the Result is there, it will give back a result or message to A or B. </li>
<li>are implementing a <code>ServiceConnection</code>-Object. In the Method <code>onServiceConnected</code> from the <code>ServiceConnection</code>-Object, the Handler will be given to the Service C. </li>
<li>If i leave A or B, the Handler for the Service will be set to Null in <code>onStop()</code>. This is because the Activity is not active anymore, so it can not use the Result to do something for example showing a Dialog.</li>
</ul>

<p>I have following Problem: </p>

<ul>
<li>If i start A and use a function from C everything works fine. Resultdialog is showing up.</li>
<li>If i start B from A, also everything works fine. Resultdialog is showing up.</li>
<li>Now if i press Back to go back to A, then C cannot contact A, cause the handler is still set to null. No Handler created Dialog is showing up.</li>
</ul>

<p>I think it has to do something with the order of the lifecycle-methodcalls. <code>onStart()</code> for the new Activity is getting called before <code>onStop()</code> from the old activity.</p>
