How to minify a Flutter app with Proguard?

Asked 20/9, 2018 at 15:55 Answered 18/3 at 13:59

Solved android dart flutter proguard minify

I already made a Flutter app. The release apk is about 14MB. I searched methods to minify this and found this ons: https://flutter.io/android-release/#enabling-proguard

But my question is, how can I get to know all my used additional libraries for step 1? Are there any commands to know them or is it just all the dependencies that I added to the pubspec.yaml ?

How do I need to implement them in this file /android/app/proguard-rules.pro?

Technical answered 20/9, 2018 at 15:55 Comment(5)

I doubt pro guard will do much. Dart compile use tree shaking already. So unless you code directly in Java (which is unlikely), the win is minimal. Maybe that size comes from your assets. – Uninspired 20/9, 2018 at 16:8

That's possible, but at least I could give it a try if I know what rules I need to add to the proguard-rules.pro file. – Technical 20/9, 2018 at 16:18

Possible duplicate of Flutter apps are too big in size – Champlain 20/9, 2018 at 18:26

medium.com/@swav.kulinski/… – Permanent 10/4, 2019 at 11:19

Did you find the answer for your question ? If yes, please share the answer. – Corsica 25/10, 2020 at 18:45

First, we will enable shrinking and obfuscation in the build file. Find build.gradle file which sits inside /android/app/ folder and add lines in bold

android {

    ...

    buildTypes {
        release {
            signingConfig signingConfigs.debug     

            minifyEnabled true
            useProguard true

            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro' 

        }
    }
}

Next we will create a configuration which will preserve entire Flutter wrapper code. Create /android/app/proguard-rules.pro file and insert inside:

#Flutter Wrapper
-keep class io.flutter.app.** { *; }
-keep class io.flutter.plugin.**  { *; }
-keep class io.flutter.util.**  { *; }
-keep class io.flutter.view.**  { *; }
-keep class io.flutter.**  { *; }
-keep class io.flutter.plugins.**  { *; }

Note: Use signingConfigs.release instead signingConfigs.debug to build a apk or appbundle

Ulloa answered 5/12, 2019 at 19:23 Comment(2)

don't use this line for release apk--> signingConfig signingConfigs.debug use --> signingConfig signingConfigs.release – Retire 17/4, 2021 at 5:30

Any update on proguard for flutter wrapper code? Where do I find these default proguard lines? – Argument 28/3, 2023 at 2:29

I will leave this answer here as an addition for any poor soul that has to deal with this issue and encounters this thread.

As of December 2021 with the latest Android Sdk, Studio and Flutter versions, if you try to douseProguard true it will not work because it's obsolete. Sadly, Gradle will not tell you this, instead, you will get an error like this:

A problem occurred evaluating project ':app'.

> No signature of method: build_7cqkbrda1q788z3b02yxbvrx9.android() is applicable for argument types: (build_7cqkbrda1q788z3b02yxbvrx9$_run_closure2) values: [build_7cqkbrda1q788z3b02yxbvrx9$_run_closure2@41108b15]

Which as you can see it is complete gibberish and not useful. The secret is to just not use useProguard at all. By default Flutter is setup to use R8 which handles minification now on Android.

Here is a so post about this for reference: Gradle : DSL element 'useProguard' is obsolete and will be removed soon

Bimonthly answered 8/12, 2021 at 1:19 Comment(2)

Been struggling on this for an hour now. – Alanna 2/2, 2022 at 10:42

You are n live safer. I still have one question: When I publish my app to play store it sill warns me that proguard is missing. Is this normal? – Humanize 1/4, 2022 at 15:8

Latest Solution

At first you should use shrinkResources true instead of useProguard true in android/app/build.gradle.

In second instead of using proguard-android.txt you should use proguard-android-optimize.txt.

[Update] Attention: If you don't want to optimize, use the proguard-android.txt configuration file instead of this one, which turns off the optimization flags. Adding optimization introduces certain risks, since for example not all optimizations performed by ProGuard works on all versions of Dalvik. To check how to turn off various optimization you need to read more at official Google Proguard reference.

buildTypes {
              
    release {
         signingConfig signingConfigs.release

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

Following is newer version of proguard configuration rules to prevent logging and other retrofit protection:

# Flutter
-keep class io.flutter.app.** { *; }
-keep class io.flutter.plugin.** { *; }
-keep class io.flutter.util.** { *; }
-keep class io.flutter.view.** { *; }
-keep class io.flutter.** { *; }
-keep class io.flutter.plugins.** { *; }

# Retrofit
-keepattributes Signature
-keepattributes Exceptions

# OkHTTP
-dontwarn okhttp3.**
-keep class okhttp3.**{ *; }
-keep interface okhttp3.**{ *; }

# Other
-keepattributes *Annotation*
-keepattributes SourceFile, LineNumberTable

# Logging 
-assumenosideeffects class android.util.Log {
    public static *** d(...);
    public static *** v(...);
    public static *** i(...);
    public static *** w(...);
    public static *** e(...);
    public static *** wtf(...);
}

-assumenosideeffects class io.flutter.Log {
    public static *** d(...);
    public static *** v(...);
    public static *** w(...);
    public static *** e(...);
}

-assumenosideeffects class java.util.logging.Level {
    public static *** w(...);
    public static *** d(...);
    public static *** v(...);
}

-assumenosideeffects class java.util.logging.Logger {
    public static *** w(...);
    public static *** d(...);
    public static *** v(...);
}

# Removes third parties logging
-assumenosideeffects class org.slf4j.Logger {
    public *** trace(...);
    public *** debug(...);
    public *** info(...);
    public *** warn(...);
    public *** error(...);
}

To check it, install jadx and open your_app.apk and search inside of that about log. You should have comparison between non-proguard .apk and proguard configured .apk log search result.

Latest Solution

Without Proguard rules

With Proguard rules

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