android using proguard, stack trace? - debugging

Question

I tested my app, and in the emulator and on my device it is working without errors.
I export my eclipse-project with proguard option enabled.
The resulting apk is crashing when I open a custom dialog http://code.google.com/p/dateslider/.
I tried the -keep options for all the classes I used, but no result.
From what I have read, is that I need the trace of the crash., to debug.
Where is it?, only a dialog is shown telling me that the app has crashed.
Jos
EDIT
Thanks to Sean's suggestions I narrow it down to a call of the method "SetContentView". It tried to load data from a layout.
<?xml version="1.0" encoding="utf-8"?>
<nl.zonneveld.pldkal_free.SliderContainer
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res/nl.zonneveld.pldkal_free"
android:id="#+id/dateSliderContainer"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<nl.zonneveld.pldkal_free.ScrollLayout
style="#style/Scroller"
app:labelerClass="nl.zonneveld.pldkal_free.YearLabeler"
app:labelerFormat="%tY"
app:childWidth="150dp"/>
<nl.zonneveld.pldkal_free.ScrollLayout
style="#style/Scroller"
app:labelerClass="nl.zonneveld.pldkal_free.MonthLabeler"
app:labelerFormat="%tB"
app:childWidth="200dp"/>
<include layout="#layout/dialogbuttons"/>
</nl.zonneveld.pldkal_free.SliderContainer>
EDIT
The uknown exception is triggered at
Class<?> klazz = Class.forName(className);
Constructor<?> ctor = klazz.getConstructor(String.class);
className="nl.zonneveld.pldkal_free.YearLabeler".
constructor of YearLabeler:
public YearLabeler(String formatString)
I tried the folowing proguard options, no succes.
-keep public class * extends nl.zonneveld.pldkal_free.YearLabeler{
public <init>(java.lang.String);
}
-keep public class * extends nl.zonneveld.pldkal_free.MonthLabeler{
public <init>(java.lang.String);
}
-keep public class * extends nl.zonneveld.pldkal_free.Labeler{
public <init>(int, int);
}

Answer 1

What is the error -- ClassNotFoundError? Meaning, you think Proguard optimized away that class? You can test that easily by setting -dontshrink, to start. If that doesn't fix it, Proguard isn't the problem.
You can obtain all log output with adb logcat on the command line. There's probably an equivalent for the Eclipse-integrated tools, but I don't know what it is. You can also use the aLogcat app on Android to see the logs.

Answer 2

After a lot of digging, this was the solution. Thanks Sean for the suggestions.
-keep public class * extends nl.zonneveld.pldkal_free.YearLabeler
-keepclassmembers class nl.zonneveld.pldkal_free.YearLabeler{
public <init>(java.lang.String);
}
-keep public class * extends nl.zonneveld.pldkal_free.MonthLabeler
-keepclassmembers class nl.zonneveld.pldkal_free.MonthLabeler{
public <init>(java.lang.String);
}
-keep public class * extends nl.zonneveld.pldkal_free.Labeler
-keepclassmembers class nl.zonneveld.pldkal_free.Labeler{
public <init>(int, int);
}