ProGuard and Gson on Android (ClassCastException)

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I am having a hell of a time with Gson and ProGuard. I have a simple object and when I parse tojson, save to sqllite and read back from the database in order to load the json back to my object, I get a java.lang.classcastexception. If I dont use ProGuard, everthing works fine.

I have verified that the json string being sent to and gotten from the database is the same. The exception is not thrown when it converts from json, but rather when I try to access the object.

Here is my simple object:

public class ScanLog extends ArrayList<SingleFrame>
{
     private static final long serialVersionUID = 1L;

     public ScanLog()
     {

     }
}

public final class SingleFrame 
{
    public int Position;
    public int Time;
    public Map<Integer,String> MainDataMap;
    public Map<Integer,String> DataMap;

    public SingleFrame(int position, int time, 
                    Map<Integer,String> mainDataMap, Map<Integer,String> dataMap)
    {
        this.Position = position;
        this.Time = time;
        this.MainDataMap = mainDataMap;
        this.DataMap = dataMap;
    }

}

All other aspects of my app are fine, but something with proguard is causing this to happen....Ive tried all kinds of -keep commands in the proguard.cfg but I am not sure what Im doing is right.

EDIT - ADDING PROGUARD.CFG

-dontusemixedcaseclassnames
-dontskipnonpubliclibraryclasses
-dontpreverify
-verbose
-dontshrink
-dontoptimize

-keep public class * extends android.app.Activity
-keep public class * extends android.app.Application
-keep public class * extends android.app.Service
-keep public class * extends android.content.BroadcastReceiver
-keep public class * extends android.content.ContentProvider
-keep public class * extends android.app.backup.BackupAgentHelper
-keep public class * extends android.preference.Preference
-keep public class com.android.vending.licensing.ILicensingService

#keep all classes that might be used in XML layouts
-keep public class * extends android.view.View
-keep public class * extends android.app.Fragment
-keep public class * extends android.support.v4.Fragment

#keep all classes
-keep public class *{
public protected *;
}

#keep all public and protected methods that could be used by java reflection
-keepclassmembernames class * {
    public protected <methods>;
}


-keepclasseswithmembernames class * {
    native <methods>;
}

-keep public class org.scanner.scanlog.SingleFrame


-keepclassmembers class org.scanner.scanlog.ScanLog { 
        private <fields>; 
        public <fields>; 
}

-keepclassmembers class org.scanner.scanlog.SingleFrame { 
        private <fields>; 
        public <fields>; 
}

-keepclasseswithmembernames class * {
    public <init>(android.content.Context, android.util.AttributeSet);
}

-keepclasseswithmembernames class * {
    public <init>(android.content.Context, android.util.AttributeSet, int);
}

-keepclassmembers enum * {
    public static **[] values();
    public static ** valueOf(java.lang.String);
}

-keep class * implements android.os.Parcelable {
  public static final android.os.Parcelable$Creator *;
}

-dontwarn **CompatHoneycomb
-dontwarn org.htmlcleaner.*
#-keep class android.support.v4.** { *; }

EDIT - Okay I got ACRA set up successfully in my app, pretty awesome feature! Here is the stack trace:

java.lang.ClassCastException: java.lang.Object
    at org.scanner.activity.ReaderMainActivity.AdvanceScanLog(SourceFile:1499)
    at org.scanner.activity.r.onProgressChanged(SourceFile:271)
    at android.widget.SeekBar.onProgressRefresh(SeekBar.java:89)
    at android.widget.ProgressBar.doRefreshProgress(ProgressBar.java:507)
    at android.widget.ProgressBar.refreshProgress(ProgressBar.java:516)
    at android.widget.ProgressBar.setProgress(ProgressBar.java:565)
    at android.widget.AbsSeekBar.trackTouchEvent(AbsSeekBar.java:337)
    at android.widget.AbsSeekBar.onTouchEvent(AbsSeekBar.java:292)
    at android.view.View.dispatchTouchEvent(View.java:3932)
    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:906)
    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:906)
    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:906)
    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:906)
    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:906)
    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:906)
    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:906)
    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:906)
    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:906)
    at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1784)
    at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1157)
    at android.app.Activity.dispatchTouchEvent(Activity.java:2181)
    at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1759)
    at android.view.ViewRoot.deliverPointerEvent(ViewRoot.java:2336)
    at android.view.ViewRoot.handleMessage(ViewRoot.java:1976)
    at android.os.Handler.dispatchMessage(Handler.java:99)
    at android.os.Looper.loop(Looper.java:143)
    at android.app.ActivityThread.main(ActivityThread.java:4263)
    at java.lang.reflect.Method.invokeNative(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:507)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
    at dalvik.system.NativeStart.main(Native Method)
8 Answers

Just to add to all of the other answers, if you guys reached here, it means that you want to obfuscate your code AND use Gson.

If, at the end, you chose to -keep class your instances, it means that these Gson classes WILL NOT BE OBFUSCATED and this solution (or even Gson in general, is not an optimal solution for you).

In this case I would advise to Serialize the classes yourself and store them See @Jessy's answer.

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