DNS: backward compatibility

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

@@ -104,6 +104,7 @@ public class DnsHelper {
     @NonNull
     private static DnsRecord[] _lookup(Context context, String name, String type, int timeout) {
         SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
+        boolean dns_custom = prefs.getBoolean("dns_custom", false);
         boolean dns_secure = prefs.getBoolean("dns_secure", false);
 
         String filter = null;
@@ -141,7 +142,7 @@ public class DnsHelper {
             ResolverApi resolver = DnssecResolverApi.INSTANCE;
             AbstractDnsClient client = resolver.getClient();
 
-            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q)
+            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q && !dns_custom)
                 client.setDataSource(new AbstractDnsDataSource() {
                     private IOException ex;
                     private DnsQueryResult result;

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

@@ -94,8 +94,8 @@ public class FragmentOptionsConnection extends FragmentBase implements SharedPre
     private SwitchCompat swPreferIp4;
     private SwitchCompat swBindSocket;
     private SwitchCompat swStandaloneVpn;
-    private EditText etDns;
     private SwitchCompat swDnsCustom;
+    private EditText etDnsExtra;
     private SwitchCompat swDnsSecure;
     private SwitchCompat swTcpKeepAlive;
     private SwitchCompat swSslUpdate;
@@ -162,8 +162,8 @@ public class FragmentOptionsConnection extends FragmentBase implements SharedPre
         swPreferIp4 = view.findViewById(R.id.swPreferIp4);
         swBindSocket = view.findViewById(R.id.swBindSocket);
         swStandaloneVpn = view.findViewById(R.id.swStandaloneVpn);
-        etDns = view.findViewById(R.id.etDns);
         swDnsCustom = view.findViewById(R.id.swDnsCustom);
+        etDnsExtra = view.findViewById(R.id.etDnsExtra);
         swDnsSecure = view.findViewById(R.id.swDnsSecure);
         swTcpKeepAlive = view.findViewById(R.id.swTcpKeepAlive);
         swSslUpdate = view.findViewById(R.id.swSslUpdate);
@@ -343,7 +343,17 @@ public class FragmentOptionsConnection extends FragmentBase implements SharedPre
             }
         });
 
-        etDns.addTextChangedListener(new TextWatcher() {
+        swDnsCustom.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
+            @Override
+            public void onCheckedChanged(CompoundButton buttonView, boolean checked) {
+                DnsHelper.clear(buttonView.getContext());
+                prefs.edit().putBoolean("dns_custom", checked).apply();
+                etDnsExtra.setEnabled(checked || Build.VERSION.SDK_INT < Build.VERSION_CODES.Q);
+                swDnsSecure.setEnabled(checked);
+            }
+        });
+
+        etDnsExtra.addTextChangedListener(new TextWatcher() {
             @Override
             public void beforeTextChanged(CharSequence s, int start, int count, int after) {
                 // Do nothing
@@ -360,15 +370,6 @@ public class FragmentOptionsConnection extends FragmentBase implements SharedPre
             }
         });
 
-        swDnsCustom.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
-            @Override
-            public void onCheckedChanged(CompoundButton buttonView, boolean checked) {
-                DnsHelper.clear(buttonView.getContext());
-                prefs.edit().putBoolean("dns_custom", checked).apply();
-                swDnsSecure.setEnabled(checked);
-            }
-        });
-
         swDnsSecure.setVisibility(debug || BuildConfig.DEBUG ? View.VISIBLE : View.GONE);
         swDnsSecure.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
             @Override
@@ -759,8 +760,9 @@ public class FragmentOptionsConnection extends FragmentBase implements SharedPre
             swPreferIp4.setChecked(prefs.getBoolean("prefer_ip4", true));
             swBindSocket.setChecked(prefs.getBoolean("bind_socket", false));
             swStandaloneVpn.setChecked(prefs.getBoolean("standalone_vpn", false));
-            etDns.setText(prefs.getString("dns_extra", null));
             swDnsCustom.setChecked(prefs.getBoolean("dns_custom", false));
+            etDnsExtra.setText(prefs.getString("dns_extra", null));
+            etDnsExtra.setEnabled(swDnsCustom.isEnabled() || Build.VERSION.SDK_INT < Build.VERSION_CODES.Q);
             swDnsSecure.setChecked(prefs.getBoolean("dns_secure", false));
             swDnsSecure.setEnabled(swDnsCustom.isChecked());
             swTcpKeepAlive.setChecked(prefs.getBoolean("tcp_keep_alive", false));

app/src/main/res/layout/fragment_options_connection.xml

@@ -423,10 +423,22 @@
                     app:layout_constraintTop_toBottomOf="@id/swBindSocket"
                     app:switchPadding="12dp" />
 
+                <androidx.appcompat.widget.SwitchCompat
+                    android:id="@+id/swDnsCustom"
+                    android:layout_width="0dp"
+                    android:layout_height="wrap_content"
+                    android:layout_marginTop="12dp"
+                    android:text="@string/title_advanced_dns_custom"
+                    app:layout_constraintEnd_toEndOf="parent"
+                    app:layout_constraintStart_toStartOf="parent"
+                    app:layout_constraintTop_toBottomOf="@id/swStandaloneVpn"
+                    app:switchPadding="12dp" />
+
                 <TextView
                     android:id="@+id/tvDns"
                     android:layout_width="0dp"
                     android:layout_height="wrap_content"
+                    android:layout_marginStart="12dp"
                     android:layout_marginTop="12dp"
                     android:layout_marginEnd="48dp"
                     android:text="@string/title_advanced_dns"
@@ -434,10 +446,10 @@
                     android:textColor="?android:attr/textColorPrimary"
                     app:layout_constraintEnd_toEndOf="parent"
                     app:layout_constraintStart_toStartOf="parent"
-                    app:layout_constraintTop_toBottomOf="@id/swStandaloneVpn" />
+                    app:layout_constraintTop_toBottomOf="@id/swDnsCustom" />
 
                 <eu.faircode.email.EditTextPlain
-                    android:id="@+id/etDns"
+                    android:id="@+id/etDnsExtra"
                     android:layout_width="0dp"
                     android:layout_height="wrap_content"
                     android:layout_marginEnd="48dp"
@@ -448,17 +460,6 @@
                     app:layout_constraintStart_toStartOf="parent"
                     app:layout_constraintTop_toBottomOf="@id/tvDns" />
 
-                <androidx.appcompat.widget.SwitchCompat
-                    android:id="@+id/swDnsCustom"
-                    android:layout_width="0dp"
-                    android:layout_height="wrap_content"
-                    android:layout_marginTop="12dp"
-                    android:text="@string/title_advanced_dns_custom"
-                    app:layout_constraintEnd_toEndOf="parent"
-                    app:layout_constraintStart_toStartOf="parent"
-                    app:layout_constraintTop_toBottomOf="@id/etDns"
-                    app:switchPadding="12dp" />
-
                 <androidx.appcompat.widget.SwitchCompat
                     android:id="@+id/swDnsSecure"
                     android:layout_width="0dp"
@@ -468,7 +469,7 @@
                     android:text="@string/title_advanced_dns_secure"
                     app:layout_constraintEnd_toEndOf="parent"
                     app:layout_constraintStart_toStartOf="parent"
-                    app:layout_constraintTop_toBottomOf="@id/swDnsCustom"
+                    app:layout_constraintTop_toBottomOf="@id/etDnsExtra"
                     app:switchPadding="12dp" />
 
                 <androidx.appcompat.widget.SwitchCompat