Example of how to intercept and block request with Android WebView

Android_WebView_Blocking.kt

package com.joshuatz.webviewblock

import android.os.Bundle
import android.util.Log
import android.webkit.*
import androidx.appcompat.app.AppCompatActivity

// Leave off www.
val BannedDomains: Array<String> = arrayOf("facebook.com", "connect.facebook.net")
val BannedUrlPatterns: Array<Regex> = arrayOf(Regex("\\.taboola\\."))

class MainActivity : AppCompatActivity() {
    private var webViewInstance: WebView? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val webView: WebView = findViewById(R.id.mainWebView)
        webViewInstance = webView

        webView.webViewClient = object : WebViewClient() {

            override fun shouldInterceptRequest(
                view: WebView,
                request: WebResourceRequest
            ): WebResourceResponse? {
                val shouldBlock = filterNetworkRequests(webView, request);

                if (shouldBlock) {
                    return WebResourceResponse("text/javascript", "UTF-8", null)
                }

                return null
            }

            override fun shouldOverrideUrlLoading(
                view: WebView,
                request: WebResourceRequest
            ): Boolean {
                return filterNetworkRequests(view, request)
            }
        }

        webView.webChromeClient = object : WebChromeClient() {
            // There are overrideable methods in here that we could hook into,
            // but we don't actually need them for network request interception
        }

        webView.loadUrl("https://joshuatz.com")
    }

    /**
     * This is our re-usable function that can be called by both `shouldOverrideUrlLoading` and
     * by `shouldInterceptRequest`
     */
    fun filterNetworkRequests(view: WebView, request: WebResourceRequest): Boolean {
        // By default, let all requests pass through
        var shouldBlock = false;
        val reqUri = request.url
        val reqUrl = reqUri.toString()

        if (BannedDomains.contains(reqUri.host?.replace("www.", ""))) {
            shouldBlock = true
        }

        for (bannedPattern in BannedUrlPatterns) {
            if (!shouldBlock) {
                shouldBlock = bannedPattern.containsMatchIn(reqUrl)
            }
        }

        return shouldBlock
    }
}