Add option to reset to default DNS servers

src/main/java/eu/siacs/conversations/ui/fragment/settings/ConnectionSettingsFragment.java

@@ -1,17 +1,27 @@
 package eu.siacs.conversations.ui.fragment.settings;
 
+import android.content.Context;
+import android.content.SharedPreferences;
 import android.os.Bundle;
 import android.widget.Toast;
 
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
+import androidx.preference.EditTextPreference;
+import androidx.preference.ListPreference;
+import androidx.preference.Preference;
+import androidx.preference.PreferenceManager;
 
 import com.google.common.base.Strings;
 
+import java.io.File;
+
 import eu.siacs.conversations.AppSettings;
 import eu.siacs.conversations.Config;
 import eu.siacs.conversations.R;
 import eu.siacs.conversations.services.QuickConversationsService;
+import eu.siacs.conversations.ui.activity.SettingsActivity;
+import eu.siacs.conversations.utils.ChatBackgroundHelper;
 
 public class ConnectionSettingsFragment extends XmppPreferenceFragment {
 
@@ -39,6 +49,25 @@ public class ConnectionSettingsFragment extends XmppPreferenceFragment {
             groupsAndConferences.setVisible(false);
             channelDiscovery.setVisible(false);
         }
+
+        final var resetDNSServerPreference = findPreference("reset_dns_server");
+        if (resetDNSServerPreference != null) {
+            resetDNSServerPreference.setOnPreferenceClickListener(preference -> {
+
+                final var dnsv4Server = (EditTextPreference) findPreference("dns_server_ipv4");
+                if (dnsv4Server != null) {
+                    dnsv4Server.setText("194.242.2.2");
+                }
+
+                final var dnsv6Server = (EditTextPreference) findPreference("dns_server_ipv6");
+                if (dnsv6Server != null) {
+                    dnsv6Server.setText("[2a07:e340::2]");
+                }
+
+                Toast.makeText(requireSettingsActivity(),R.string.dns_server_reset,Toast.LENGTH_LONG).show();
+                return true;
+            });
+        }
     }
 
     @Override
@@ -70,4 +99,15 @@ public class ConnectionSettingsFragment extends XmppPreferenceFragment {
         super.onStart();
         requireActivity().setTitle(R.string.pref_connection_options);
     }
+
+    public SettingsActivity requireSettingsActivity() {
+        final var activity = requireActivity();
+        if (activity instanceof SettingsActivity settingsActivity) {
+            return settingsActivity;
+        }
+        throw new IllegalStateException(
+                String.format(
+                        "%s is not %s",
+                        activity.getClass().getName(), SettingsActivity.class.getName()));
+    }
 }

src/main/res/drawable/outline_reset_settings_24.xml

@@ -0,0 +1,5 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android" android:height="24dp" android:tint="?colorControlNormal" android:viewportHeight="960" android:viewportWidth="960" android:width="24dp">
+      
+    <path android:fillColor="@android:color/white" android:pathData="M520,630L520,570L680,570L680,630L520,630ZM580,840L580,790L520,790L520,730L580,730L580,680L640,680L640,840L580,840ZM680,790L680,730L840,730L840,790L680,790ZM720,680L720,520L780,520L780,570L840,570L840,630L780,630L780,680L720,680ZM831,400L748,400Q722,312 649,256Q576,200 480,200Q363,200 281.5,281.5Q200,363 200,480Q200,552 232.5,612Q265,672 320,710L320,600L400,600L400,840L160,840L160,760L254,760Q192,710 156,637.5Q120,565 120,480Q120,405 148.5,339.5Q177,274 225.5,225.5Q274,177 339.5,148.5Q405,120 480,120Q609,120 706.5,199.5Q804,279 831,400Z"/>
+    
+</vector>

src/main/res/values/strings.xml

@@ -1317,4 +1317,7 @@
     <string name="direct_messages">Direct messages</string>
     <string name="channels">Channels</string>
     <string name="manage_account">Manage account</string>
+    <string name="pref_reset_dns_server_summary">Reset to the default DNS servers. A phone restart is needed.</string>
+    <string name="pref_reset_dns_server_title">Reset DNS</string>
+    <string name="dns_server_reset">DNS reset</string>
 </resources>

src/main/res/xml/preferences_connection.xml

@@ -26,6 +26,11 @@
             android:key="dns_server_ipv6"
             android:summary="@string/pref_dns_server_ipv6_summary"
             android:title="@string/pref_dns_server_ipv6_title" />
+        <Preference
+            android:key="reset_dns_server"
+            android:icon="@drawable/outline_reset_settings_24"
+            android:summary="@string/pref_reset_dns_server_summary"
+            android:title="@string/pref_reset_dns_server_title" />
     </PreferenceCategory>
 
     <PreferenceCategory