Change the below line to pass the style
through your constructor...
private final ProgressDialog dialog = new ProgressDialog(Login.this);
to this...
private final ProgressDialog dialog = new ProgressDialog(Login.this, R.style.ProgressBar);
Update:
I just change the style
as below...and its working for.
<style name="ProgressBar" parent="@style/android:Theme.Holo">
<item name="android:textColor">#FFFFFF</item>
<item name="android:background">#000000</item>
</style>