How to configure proguard for javascript interface?

Question

I have a implemented a Webview which takes use of JavascriptInterface. It's working fine when not obfuscating, but at once Proguard is active, it does not work. I've looked here at other answers, but i still can't get it working.

Some of the WebView class:

public class Activity_Webview {
private WebView webView;

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        webView = (WebView) findViewById(R.id.webview);
        webView.getSettings().setJavaScriptEnabled(true);
        webView.addJavascriptInterface(new JavaScriptInterface (), "HTMLOUT");
        webView.setWebViewClient(mWebViewClient);
    }

    public class JavaScriptInterface implements NonObfuscateable{
        @JavascriptInterface
        public void processHTML(String html) {
        handleFinishFromWebView(html);
    }
}

What i've tried in Proguard:

-keep public class * implements com.project.NonObfuscateable
-keepclassmembers class * implements NonObfuscateable {
    public void processHTML(java.lang.String);
}

I've also tried this (when not implementing NonObfuscateable interface:

-keep public class com.project.Activity_Webview.JavaScriptInterface
-keep public class * implements com.project.Activity_Webview.JavaScriptInterface
-keepclassmembers class * implements com.project.Activity_Webview.JavaScriptInterface {
    <fields>;
    <methods>;
}

Does anybody have an idea of what could be wrong? Thanks in advance

Don't know why I use default proguard-rule.pro file (it seems not set anything) in Android Studio 4.1.2 and everything goes right after the build with minifyEnabled=true. — Shrdi
– Shrdi, Commented Mar 10, 2021 at 7:20

Eric Lafortune · Accepted Answer · 2013-07-14 07:52:38Z

50

Both your configurations could have worked if they hadn't contained typos:

ProGuard requires fully qualified names:

NonObfuscateable -> com.project.NonObfuscateable
Compiled classes use '$' as a separator for inner classes:

com.project.Activity_Webview.JavaScriptInterface -> com.project.Activity_Webview$JavaScriptInterface

In the console log, ProGuard prints out notes about such suspected typos.

A more general solution for keeping annotated Javascript interface methods:

-keepclassmembers class * {
    @android.webkit.JavascriptInterface <methods>;
}

answered Jul 14, 2013 at 7:52

Eric Lafortune

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1 Comment

Miha_x64 Over a year ago

With newer ProGuard we should use -keepclassmembers,allowoptimization, right?

Community · Accepted Answer · 2017-05-23 12:10:41Z

5

If you're using obfuscation, in addition to Eric Lafortune's answer you also need:

-keepattributes JavascriptInterface

http://proguard.sourceforge.net/manual/usage.html#obfuscationoptions

edited May 23, 2017 at 12:10

CommunityBot

11 silver badge

answered Jan 19, 2015 at 21:57

Heath Borders

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1 Comment

Pierre-Luc Paour Over a year ago

Indeed, according to a statement by @Eric Lafortune on a bug report, "ProGuard is currently agnostic about the meaning of any annotations". That's unfortunate… sourceforge.net/p/proguard/bugs/491

Tapa Save · Accepted Answer · 2015-12-26 15:09:24Z

In my case work only code:

proguard.cfg:

-dontwarn

-keepattributes Signature
-keepattributes SetJavaScriptEnabled
-keepattributes JavascriptInterface
-keepattributes InlinedApi
-keepattributes SourceFile,LineNumberTable
-keepattributes *Annotation*

-keepclassmembers class * {
    @android.webkit.JavascriptInterface <methods>;
}
-keepclassmembers class * {
    @android.webkit.JavascriptInterface <methods>;
}
-keepclassmembers class **.*$MyJavascriptInterface {
    *;
}
-keepclassmembers class **.*$JavaScriptInterface {
    *;
}

-keep public class **.*$MyJavascriptInteface
-keep public class **.*$JavaScriptInterface

Java code:

@SuppressLint("SetJavaScriptEnabled")
public class ActivityWebView extends Activity {
    ...
    webView.getSettings().setJavaScriptEnabled(true);
    webView.addJavascriptInterface(new MyJavascriptInterface(MyActivity.this), "MyJSI");

    ....

    public class MyJavaScriptInterface {

        Context context;

        MyJavascriptInterface(Context context) {
        this.context = context;
        }

        @JavascriptInterface
        @SuppressWarnings("unused")
        public void myjavascriptfunction() {
            ...
        }

    }
    ...
}

sudo nano · Accepted Answer · 2025-11-11 16:56:00Z

0

This is the only thing that worked for me:

-keepclassmembers class * { @android.webkit.JavascriptInterface <methods>; }
-keepattributes *Annotation*

According to the proguard docs, things like -keepattributes JavascriptInterface aren't supposed to do anything at all, as JavascriptInterface is not in the list of attributes recognized by proguard.

answered Nov 11 at 16:56

sudo nano

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