ClassCastException while executing my app with minifyEnabled true

Question

I have an Android system app that has a custom BroadCastReceiver in manifest (this is to be run in Android M device): My manifest:

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    android:sharedUserId="android.uid.system"
    package="mypackagename">

   ....

    <!-- custom permissions -->
    <uses-permission android:name="mypackagename.ASK_DISPLAY_INFO"
        android:protectionLevel="signatureOrSystem"/>

    <permission android:name="mypackagename.ASK_DISPLAY_INFO" />


    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
         
        ....

        <!-- custom receiver -->
        <receiver android:name=".CustomReceiver"
            android:permission="mypackagename.ASK_DISPLAY_INFO">
            <intent-filter>
                <action android:name="GET_HDMI_SUPPORTED_MODES"/>
                <action android:name="CHANGE_HDMI_RESOLUTION"/>
            </intent-filter>
        </receiver>



    </application>

</manifest>

And I have enabled in gradle Proguard obfuscation:

        release {
            minifyEnabled true
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
         
        }

I have another test app that sends broadcasts to this app. The thing is, with mignifyEnabled false works, but with mignifyEnabled true when receives a broadcast intent it gives the error:

java.lang.RuntimeException: Unable to instantiate receiver mypackagename.CustomReceiver: java.lang.ClassCastException: mypackagename.CustomReceiver cannot be cast to android.content.BroadcastReceiver

Adding the following rule to proguard-rules.pro:

-keep class android.content.BroadcastReceiver { *; }

When receiving an intent throws the error:

java.lang.AbstractMethodError: abstract method "void android.content.BroadcastReceiver.onReceive(android.content.Context, android.content.Intent)"

Here is my broadcastreceiver definition:


import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.os.AsyncTask;
import android.util.Log;


public class CustomReceiver extends BroadcastReceiver {
    ...

    @Override
    public void onReceive(Context context, Intent intent) {
        if (intent.getAction() != null) {
            Log.i(TAG, "CustomReceiver received action: "+intent.getAction());

            if (intent.getAction().equals(GET_HDMI_SUPPORTED_MODES)) {
                new GetHDMIModesTask(context).execute();
            }  else if (intent.getAction().equals(CHANGE_HDMI_RESOLUTION) && intent.getExtras() != null && intent.hasExtra(EXTRA_HDMI_MODE) ) {
                new ChangeHDMIModeTask(context, intent.getStringExtra(EXTRA_HDMI_MODE)).execute();
            }
        }

    }

}

As I'm very new to Proguard rules and I need this obfuscated, I would appreciate if someone can tell me which rules can I specify to solve this issue

seems like the issue is in CustomReceiver so post make sure it extends BroadcastReceiver and imports are appropriate — Pavneet_Singh
– Pavneet_Singh, Commented Jan 21, 2020 at 17:31
Hello, thanks, for your answer, I've added my broadcastreceiver to the post. — alex
– alex, Commented Jan 22, 2020 at 9:54
if you are using broadcast with separate apps then add android:exported="true" though for pro guard, the answer by Nikhil should fix the issue, clean and generate new apk and try again — Pavneet_Singh
– Pavneet_Singh, Commented Jan 22, 2020 at 11:39

NIKHIL AGGARWAL · Accepted Answer · 2020-01-22 08:34:34Z

0

Add -keep public class * extends android.content.BroadcastReceiver to your proguard rules instead of -keep class android.content.BroadcastReceiver { *; }. This will prevent your custom broadcast receiver from being obfuscated.

answered Jan 22, 2020 at 8:34

NIKHIL AGGARWAL

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11 Comments

alex Over a year ago

Hello, thanks for your suggestion, I've added to proguard rules: -keep public class * extends android.content.BroadcastReceiver but still returns the first error: java.lang.RuntimeException: Unable to instantiate receiver mypackagename.CustomReceiver: java.lang.ClassCastException: mypackagename.CustomReceiver cannot be cast to android.content.BroadcastReceiver

NIKHIL AGGARWAL Over a year ago

Try keeping both lines - -keep public class * extends android.content.BroadcastReceiver and -keep class android.content.BroadcastReceiver { *; }

alex Over a year ago

Adding both rules throws the second error: java.lang.AbstractMethodError: abstract method "void android.content.BroadcastReceiver.onReceive(android.content.Context, android.content.Intent)

NIKHIL AGGARWAL Over a year ago

Try adding -keepnames class your.package.name.ClassName { } to explicity tell proguard not to obfuscate the class.

alex Over a year ago

it doesn't build: AGPBI: {"kind":"error","text":"Expected [!]interface|@interface|class|enum","sources":[{"file":"C:\\...\proguard-rules.pro","position":{"startLine":34,"startColumn":11,"startOffset":1295}}],"tool":"R8"} FAILURE: Build failed with an exception.

|

alex · Accepted Answer · 2020-02-17 11:08:26Z

0

I have done a workaround in this, removed CustomerReceiver from manifest, added an custom application class and defined the BroadcastReceiver in there. Added the proguard rules:

 -keep class android.app.Application {
        public <fields>;
        private <fields>;
       public <methods>;
    }

    -keep public class * extends android.app.Application

The issue was gone

answered Feb 17, 2020 at 11:08

alex

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