How to use ServiceWorkerController on Android

Question

I came across ServiceWorkerController while looking through the Android WebView documentation and decided to give it a try. Unfortunately I have been unable to get intercept any calls. I am aware of WebViewClient.shouldInterceptRequest but am interested in learning more about the ServiceWorkerController. Unfortunately the documents are a little sparse beyond what I have already implemented below. Any help would be appreciated.

I have put together a simple app consisting of a single Activity.

package com.example.myapplication;


import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.webkit.ServiceWorkerClient;
import android.webkit.ServiceWorkerController;
import android.webkit.WebResourceRequest;
import android.webkit.WebResourceResponse;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;

public class MainActivity extends Activity {
    private final static String LOGTAG = MainActivity.class.getSimpleName();

    private WebView mWebView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        ServiceWorkerController.getInstance().setServiceWorkerClient(new ServiceWorkerClient() {
            @Override
            public WebResourceResponse shouldInterceptRequest(WebResourceRequest request) {
                Log.e(LOGTAG, "in service worker");
                return null;
            }
        });

        setContentView(R.layout.activity_main);

        mWebView = (WebView) findViewById(R.id.activity_main_webview);

        WebSettings webSettings = mWebView.getSettings();
        webSettings.setJavaScriptEnabled(true);


        mWebView.setWebViewClient(new WebViewClient());
        Log.e(LOGTAG, "about to load URL");
        mWebView.loadUrl("https://www.google.com");
    }

    @Override
    public void onBackPressed() {
        if(mWebView.canGoBack()) {
            mWebView.goBack();
        } else {
            super.onBackPressed();
        }
    }
}

And my relevant build.gradle

apply plugin: 'com.android.application'

android {
    compileSdkVersion 29
    buildToolsVersion "29.0.2"
    defaultConfig {
        applicationId "com.example.myapplication"
        minSdkVersion 24
        targetSdkVersion 29
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'androidx.appcompat:appcompat:1.0.2'
    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'

    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'androidx.test.ext:junit:1.1.0'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.1.1'
}

user_13737427 · Answer

I have found the issue to be a misunderstanding. I had believed that installing a ServiceWorkerClient would allow for me to intercept all requests from all WebViews in my app regardless of domain. This appears to not be the case. The ServiceWorkerClient is only called if a webview has installed a ServiceWorker already. All service worker requests from all service workers are then funneled to the ServiceWorkerClient. What this means is that if you wish to intercept all network requests within all webviews in your app you will also need to override shouldInterceptRequest() on your WebViewClient as well.

package com.example.myapplication;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.webkit.ServiceWorkerClient;
import android.webkit.ServiceWorkerController;
import android.webkit.WebResourceRequest;
import android.webkit.WebResourceResponse;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;

import androidx.annotation.Nullable;


public class MainActivity extends Activity {
    private final static String LOGTAG = MainActivity.class.getSimpleName();

    private WebView mWebView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        ServiceWorkerController swController = ServiceWorkerController.getInstance();
        swController.setServiceWorkerClient(new ServiceWorkerClient() {
            @Override
            public WebResourceResponse shouldInterceptRequest(WebResourceRequest request) {
                Log.e(LOGTAG, "in service worker. isMainFrame:"+request.isForMainFrame() +": " + request.getUrl());
                return null;
            }
        });
        swController.getServiceWorkerWebSettings().setAllowContentAccess(true);

        setContentView(R.layout.activity_main);

        mWebView = (WebView) findViewById(R.id.activity_main_webview);

        WebSettings webSettings = mWebView.getSettings();
        WebView.setWebContentsDebuggingEnabled(true);
        webSettings.setJavaScriptEnabled(true);


        mWebView.setWebViewClient(new WebViewClient() {
            @Nullable
            @Override
            public WebResourceResponse shouldInterceptRequest(WebView view,
                                                              WebResourceRequest request) {
                Log.e(LOGTAG, "in webview client. isMainFrame:"+request.isForMainFrame() +": " + request.getUrl());
                return super.shouldInterceptRequest(view, request);
            }
        });
        Log.e(LOGTAG, "about to load URL");

        //service worker handler only invoked on pages with service workers
        mWebView.loadUrl("https://developers.google.com/web/fundamentals/primers/service-workers/");

    }

    @Override
    public void onBackPressed() {
        if(mWebView.canGoBack()) {
            mWebView.goBack();
        } else {
            super.onBackPressed();
        }
    }
}

How to use ServiceWorkerController on Android

1 Answers