Java tutorial
/* -*- Mode: Java; c-basic-offset: 4; tab-width: 20; indent-tabs-mode: nil; -*- * This Source Code Form is subject to the terms of the Mozilla Public * License, v. 2.0. If a copy of the MPL was not distributed with this * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ package org.mozilla.focus.webkit; import android.content.res.Resources; import android.support.v4.util.ArrayMap; import android.support.v4.util.Pair; import android.webkit.WebView; import android.webkit.WebViewClient; import org.mozilla.focus.R; import org.mozilla.focus.utils.HtmlLoader; import java.util.HashMap; import java.util.Map; public class ErrorPage { private static final HashMap<Integer, Pair<Integer, Integer>> errorDescriptionMap; static { errorDescriptionMap = new HashMap<>(); // Chromium's mapping (internal error code, to Android WebView error code) is described at: // https://chromium.googlesource.com/chromium/src.git/+/master/android_webview/java/src/org/chromium/android_webview/ErrorCodeConversionHelper.java errorDescriptionMap.put(WebViewClient.ERROR_UNKNOWN, new Pair<>(R.string.error_connectionfailure_title, R.string.error_connectionfailure_message)); // This is probably the most commonly shown error. If there's no network, we inevitably // show this. errorDescriptionMap.put(WebViewClient.ERROR_HOST_LOOKUP, new Pair<>(R.string.error_hostLookup_title, R.string.error_hostLookup_message)); // WebViewClient.ERROR_UNSUPPORTED_AUTH_SCHEME // TODO: we don't actually handle this in firefox - does this happen in real life? // WebViewClient.ERROR_AUTHENTICATION // TODO: there's no point in implementing this until we actually support http auth (#159) errorDescriptionMap.put(WebViewClient.ERROR_CONNECT, new Pair<>(R.string.error_connect_title, R.string.error_connect_message)); // It's unclear what this actually means - it's not well documented. Based on looking at // ErrorCodeConversionHelper this could happen if networking is disabled during load, in which // case the generic error is good enough: errorDescriptionMap.put(WebViewClient.ERROR_IO, new Pair<>(R.string.error_connectionfailure_title, R.string.error_connectionfailure_message)); errorDescriptionMap.put(WebViewClient.ERROR_TIMEOUT, new Pair<>(R.string.error_timeout_title, R.string.error_timeout_message)); errorDescriptionMap.put(WebViewClient.ERROR_REDIRECT_LOOP, new Pair<>(R.string.error_redirectLoop_title, R.string.error_redirectLoop_message)); // We already try to handle external URLs if possible (i.e. we offer to open the corresponding // app, if available for a given scheme). If we end up here that means no app exists. // We could consider showing an "open google play" link here, but ultimately it's hard // to know whether that's the right step, especially if there are no good apps for actually // handling such a protocol there - moreover there doesn't seem to be a good way to search // google play for apps supporting a given scheme. errorDescriptionMap.put(WebViewClient.ERROR_UNSUPPORTED_SCHEME, new Pair<>(R.string.error_unsupportedprotocol_title, R.string.error_unsupportedprotocol_message)); errorDescriptionMap.put(WebViewClient.ERROR_FAILED_SSL_HANDSHAKE, new Pair<>(R.string.error_sslhandshake_title, R.string.error_sslhandshake_message)); errorDescriptionMap.put(WebViewClient.ERROR_BAD_URL, new Pair<>(R.string.error_malformedURI_title, R.string.error_malformedURI_message)); // WebView returns ERROR_UNKNOWN when we try to access a file:/// on Android (with the error string // containing access denied), so I'm not too sure why these codes exist: // sure why these error codes exit // WebViewClient.ERROR_FILE; // WebViewClient.ERROR_FILE_NOT_FOUND; // Seems to be an indication of OOM, insufficient resources, or too many queued DNS queries errorDescriptionMap.put(WebViewClient.ERROR_TOO_MANY_REQUESTS, new Pair<>(R.string.error_generic_title, R.string.error_generic_message)); } public static boolean supportsErrorCode(final int errorCode) { return (errorDescriptionMap.get(errorCode) != null); } public static void loadErrorPage(final WebView webView, final String desiredURL, final int errorCode) { final Pair<Integer, Integer> errorResourceIDs = errorDescriptionMap.get(errorCode); if (errorResourceIDs == null) { throw new IllegalArgumentException( "Cannot load error description for unsupported errorcode=" + errorCode); } // This is quite hacky: ideally we'd just load the css file directly using a '<link rel="stylesheet"'. // However webkit thinks it's still loading the original page, which can be an https:// page. // If mixed content blocking is enabled (which is probably what we want in Focus), then webkit // will block file:///android_res/ links from being loaded - which blocks our css from being loaded. // We could hack around that by enabling mixed content when loading an error page (and reenabling it // once that's loaded), but doing that correctly and reliably isn't particularly simple. Loading // the css data and stuffing it into our html is much simpler, especially since we're already doing // string substitutions. // As an added bonus: file:/// URIs are broken if the app-ID != app package, see: // https://code.google.com/p/android/issues/detail?id=211768 (this breaks loading css via file:/// // references when running debug builds, and probably klar too) - which means this wouldn't // be possible even if we hacked around the mixed content issues. final String cssString = HtmlLoader.loadResourceFile(webView.getContext(), R.raw.errorpage_style, null); final Map<String, String> substitutionMap = new ArrayMap<>(); final Resources resources = webView.getContext().getResources(); substitutionMap.put("%page-title%", resources.getString(R.string.errorpage_title)); substitutionMap.put("%button%", resources.getString(R.string.errorpage_refresh)); substitutionMap.put("%messageShort%", resources.getString(errorResourceIDs.first)); substitutionMap.put("%messageLong%", resources.getString(errorResourceIDs.second, desiredURL)); substitutionMap.put("%css%", cssString); final String errorPage = HtmlLoader.loadResourceFile(webView.getContext(), R.raw.errorpage, substitutionMap); // We could load the raw html file directly into the webview using a file:///android_res/ // URI - however we'd then need to do some JS hacking to do our String substitutions. Moreover // we'd have to deal with the mixed-content issues detailed above in that case. webView.loadDataWithBaseURL(desiredURL, errorPage, "text/html", "UTF8", desiredURL); } }