Added network security config to allow cleartext in webview

app/src/main/AndroidManifest.xml

@@ -15,6 +15,7 @@
         android:appCategory="productivity"
         android:icon="@mipmap/ic_launcher"
         android:label="@string/app_name"
+        android:networkSecurityConfig="@xml/network_security_config"
         android:roundIcon="@mipmap/ic_launcher_round"
         android:supportsRtl="true"
         android:theme="@style/AppThemeLight">

app/src/main/java/eu/faircode/email/FragmentWebView.java

@@ -52,7 +52,7 @@ public class FragmentWebView extends FragmentEx {
         settings.setJavaScriptEnabled(true);
         settings.setLoadWithOverviewMode(true);
         settings.setUseWideViewPort(true);
-        //settings.setBuiltInZoomControls(true);
+        settings.setMixedContentMode(WebSettings.MIXED_CONTENT_ALWAYS_ALLOW);
 
         webview.setWebViewClient(new WebViewClient() {
             public boolean shouldOverrideUrlLoading(WebView view, String url) {

app/src/main/res/xml/network_security_config.xml

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="utf-8"?>
+<network-security-config>
+    <!-- https://developer.android.com/training/articles/security-config -->
+    <base-config cleartextTrafficPermitted="true">
+        <trust-anchors>
+            <certificates src="system" />
+        </trust-anchors>
+    </base-config>
+</network-security-config>