Question

I’m currently displaying a bunch of data to the user as HTML in a webview. I have some links below each entry that should call a method in my app when clicked. The Android WebView’s javascript interface seems to be the best (only?) way of handling these things. However, whenever I click the link, I get this error message: ERROR/Web Console(6112): Uncaught TypeError: Object [my namespace]@4075ff10 has no method 'edit' at [base URL]:55


I have the following interface declared:

public class JavaScriptInterface {
    Context context;

    JavaScriptInterface(Context c) {
        context = c;
    }

    public void edit(String postid) {
        Log.d("myApp", "EDIT!");
        //do stuff
    }
}

I then add it to my WebView:

final WebView threadView = (WebView) findViewById(R.id.webViewThread);
threadView.getSettings().setJavaScriptEnabled(true);
threadView.addJavascriptInterface(new JavaScriptInterface(this), "Android");

And, finally, I call this within my HTML as follows:

<div class="post-actions">
    <div class="right">
        <a onClick="Android.edit('4312244');">Edit</a>
    </div>
</div>

The real kicker is this all works when I’m debugging my app via the emulator or adb connection to my phone. When I build and publish the app, it breaks.

I’m at my wits end. Any help or advice would be greatly appreciated!

Answer 1

Same problem for my 2.3.3 mobile phone.
But as I knew one app that worked and another not, I was not happy with this workaround.
And I find out the differnce of my two apps.
The one with the broken JavaScriptInterface uses Proguard.
After a little search, I find a solution.

Short summary: interface JavascriptCallback, which is implemented by JavaScriptInterface and added rules for Proguard in proguard.conf:

public interface JavascriptCallback {

}

public class JavaScriptInterface implements JavascriptCallback {
    Context mContext;
    /** Instantiate the interface and set the context */
    JavaScriptInterface(Context c) {
        mContext = c;
    }
    /** Show a toast from the web page */
    public void showToast(String toast) {
        Toast.makeText(mContext, toast, Toast.LENGTH_SHORT).show();
    }
}

proguard.cfg:

-keep public class YOURPACKAGENAMEHERE.JavascriptCallback
-keep public class * implements YOURPACKAGENAMEHERE.JavascriptCallback
-keepclassmembers class * implements YOURPACKAGENAMEHERE.JavascriptCallback {
    <methods>;
}