Fix ProGuard obfuscation crash on state restoration after process death

[Copilot]

Tracked by https://github.com/warting/android-signaturepad/issues (minified build crash)

This PR...

Prevents ClassCastException / NullPointerException crashes in minified builds when restoring SignaturePad state after process death.

Considerations and implementation

The Event Parcelable class gets obfuscated by ProGuard/R8, causing Android's deserialization to fail in onRestoreInstanceState(). The fix adds a keep rule:

-keep class se.warting.signaturecore.Event { *; }

Changes:

• Created signature-core/consumer-rules.pro with keep rule for Event class
• Configured consumerProguardFiles("consumer-rules.pro") in signature-core/build.gradle.kts
• Added matching rule to signature-core/proguard-rules.pro for consistency

The consumerProguardFiles configuration ensures the rule is automatically applied to consuming apps via the library AAR.

How to test

1. Create a release build with minifyEnabled true
2. Draw a signature on the pad
3. Background the app and kill the process: adb shell am kill <package>
4. Restore the app from recents
5. Verify signature is restored without crash

Test(s) added

No tests added - this is a build configuration fix for ProGuard. The existing behavior (state restoration) already works in debug builds; this ensures it works in release builds.

Screenshots

Before	After
N/A - crash prevented by ProGuard rules	N/A - crash prevented by ProGuard rules

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• scans-in.gradle.com
  • Triggering command: /usr/lib/jvm/temurin-17-jdk-amd64/bin/java /usr/lib/jvm/temurin-17-jdk-amd64/bin/java --add-opens=java.base/java.lang=ALL-UNNAMED --add-opens=java.base/java.lang.invoke=ALL-UNNAMED --add-opens=java.base/java.util=ALL-UNNAMED --add-opens=java.prefs/java.util.prefs=ALL-UNNAMED --add-exports=jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED --add-exports=jdk.compiler/com.sun.tools.javac.util=ALL-UNNAMED --add-opens=java.base/java.util=ALL-UNNAMED --add-opens=java.prefs/java.util.prefs=ALL-UNNAMED --add-opens=java.base/java.nio.charset=ALL-UNNAMED --add-opens=java.base/java.net=ALL-UNNAMED --add-opens=java.base/java.util.concurrent.atomic=ALL-UNNAMED --add-opens=java.xml/javax.xml.namespace=ALL-UNNAMED -Xmx4096m -Dfile.encoding=UTF-8 -Duser.country -Duser.language=en -Duser.variant -cp /home/REDACTED/.gradle/wrapper/dists/gradle-8.14.1-bin/baw1sv0jfoi8rxs14qo3h49cs/gradle-8.14.1/lib/gradle-daemon-main-8.14.1.jar (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

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This section details on the original issue you should resolve

<issue_title>App is crashing in minified build</issue_title>
<issue_description>App is crashing in minified build.
In emulator with Android 13 , app is crashing when app brought to foreground after process death.

To Reproduce
Steps to reproduce the behavior:

1. Create emulator setting android Android 13 (Api 33)
2. Create a release build setting minifyEnabled true
3. Put signature
4. Then put the app background
5. kill the process by adb command. adb shell am kill your_package_name
6. now bring back the app fore ground

Expected behavior
App should show restore the signature

Smartphone (please complete the following information):

• Device: Emulator
• OS: Android 13

Main cause of crash
java.lang.ClassCastException: Cannot cast [Lse.warting.signaturecore.Event; to android.os.Parcelable at java.lang.Class.cast(Class.java:4183)

Crash log
Fatal Exception: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.Class.isInterface()' on a null object reference
at java.lang.Class.isAssignableFrom(Class.java:589)
at android.os.Parcel.readParcelableCreatorInternal(Parcel.java:4900)
at android.os.Parcel.readParcelableInternal(Parcel.java:4807)
at android.os.Parcel.readParcelableArrayInternal(Parcel.java:5018)
at android.os.Parcel.readValue(Parcel.java:4645)
at android.os.Parcel.readValue(Parcel.java:4347)
at android.os.Parcel.-$$Nest$mreadValue()
at android.os.Parcel$LazyValue.apply(Parcel.java:4445)
at android.os.Parcel$LazyValue.apply(Parcel.java:4404)
at android.os.BaseBundle.getValueAt(BaseBundle.java:394)
at android.os.BaseBundle.getValue(BaseBundle.java:374)
at android.os.Bundle.getParcelableArray(Bundle.java:1020)
at se.warting.signatureview.views.SignaturePad.onRestoreInstanceState(SignaturePad.kt:66)
at android.view.View.dispatchRestoreInstanceState(View.java:21631)
at android.view.ViewGroup.dispatchRestoreInstanceState(ViewGroup.java:4007)
at android.view.ViewGroup.dispatchRestoreInstanceState(ViewGroup.java:4007)
at android.view.ViewGroup.dispatchRestoreInstanceState(ViewGroup.java:4007)
at android.view.ViewGroup.dispatchRestoreInstanceState(ViewGroup.java:4007)
at android.view.ViewGroup.dispatchRestoreInstanceState(ViewGroup.java:4007)
at android.view.View.restoreHierarchyState(View.java:21609)
at androidx.fragment.app.Fragment.restoreViewState(Fragment.java:703)
at androidx.fragment.app.Fragment.restoreViewState(Fragment.java:3181)
at androidx.fragment.app.Fragment.performActivityCreated(Fragment.java:3166)
at androidx.fragment.app.FragmentStateManager.activityCreated(FragmentStateManager.java:639)
at androidx.fragment.app.FragmentStateManager.moveToExpectedState(FragmentStateManager.java:289)
at androidx.fragment.app.FragmentStore.moveToExpectedState(FragmentStore.java:114)
at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1685)
at androidx.fragment.app.FragmentManager.dispatchStateChange(FragmentManager.java:3319)
at androidx.fragment.app.FragmentManager.dispatchActivityCreated(FragmentManager.java:3237)
at androidx.fragment.app.Fragment.performActivityCreated(Fragment.java:3167)
at androidx.fragment.app.FragmentStateManager.activityCreated(FragmentStateManager.java:639)
at androidx.fragment.app.FragmentStateManager.moveToExpectedState(FragmentStateManager.java:289)
at androidx.fragment.app.FragmentStore.moveToExpectedState(FragmentStore.java:114)
at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1685)
at androidx.fragment.app.FragmentManager.dispatchStateChange(FragmentManager.java:3319)
at androidx.fragment.app.FragmentManager.dispatchActivityCreated(FragmentManager.java:3237)
at androidx.fragment.app.FragmentController.dispatchActivityCreated(FragmentController.java:263)
at androidx.fragment.app.FragmentActivity.onStart(FragmentActivity.java:350)
at androidx.appcompat.app.AppCompatActivity.onStart(AppCompatActivity.java)
at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1543)
at android.app.Activity.performStart(Activity.java:8367)
at android.app.ActivityThread.handleStartActivity(ActivityThread.java:3670)
at android.app.servertransaction.TransactionExecutor.performLifecycleSequence(TransactionExecutor.java:224)
at android.app.servertransaction.TransactionExecutor.cycleToPath(TransactionExecutor.java:204)
at android.app.servertransaction.TransactionExecutor.executeLifecycleState(TransactionExecutor.java:176)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:97)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2307)
at...

• Fixes App is crashing in minified build #433

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