How to use child activity's function on Android
<p>I use a TabHost in the main activity, HostActivity.<br>
And it contain 2 tab, ATab and BTab, which control by ActivityGroup AGroup and BGroup.<br>
And AGroup cantain 2 Activity, AActivity and BActivity.<br>
If HostActivity contain a function FunctionInHostActivity, and AActivity contain a function FunctionInAActivity.<br>
In AActivity, I want to use FunctionInHostActivity function, I can usebelow line to do it:  </p>

<pre><code>((HostActivity)this.getParent().getParent()).FunctionInHostActivity();
</code></pre>

<p>But by contrast, I want to use FunctionInAActivity in HostActivity.<br>
How can I arrive it?  </p>
