Add MQTT dependencies, settings UI, and test coverage (CATROID-1670, CATROID-1672)

catroid/build.gradle

@@ -154,6 +154,7 @@ android {
         buildConfigField "boolean", "FEATURE_NFC_ENABLED", "true"
         buildConfigField "boolean", "FEATURE_POCKETMUSIC_ENABLED", "true"
         buildConfigField "boolean", "FEATURE_RASPI_ENABLED", "true"
+        buildConfigField "boolean", "FEATURE_MQTT_ENABLED", "true"
         buildConfigField "boolean", "FEATURE_SCRATCH_CONVERTER_ENABLED", "true"
         buildConfigField "boolean", "FEATURE_USER_REPORTERS_ENABLED", "true"
         buildConfigField "boolean", "FEATURE_MULTIPLAYER_VARIABLES_ENABLED", "true"
@@ -420,6 +421,9 @@ dependencies {
     implementation 'com.google.guava:guava:28.2-android'
     implementation 'com.google.code.gson:gson:2.8.7'
 
+    // MQTT
+    implementation 'org.eclipse.paho:org.eclipse.paho.client.mqttv3:1.2.5'
+
     implementation 'com.koushikdutta.async:androidasync:2.2.1'
     implementation 'com.squareup.picasso:picasso:2.71828'
     implementation 'ar.com.hjg:pngj:2.1.0'

catroid/src/androidTest/java/org/catrobat/catroid/uiespresso/ui/activity/SettingsFragmentTest.java

@@ -85,6 +85,7 @@
 import static org.catrobat.catroid.ui.settingsfragments.SettingsFragment.SETTINGS_SHOW_PHIRO_BRICKS_CHECKBOX_PREFERENCE;
 import static org.catrobat.catroid.ui.settingsfragments.SettingsFragment.SETTINGS_SHOW_PLOT_BRICKS;
 import static org.catrobat.catroid.ui.settingsfragments.SettingsFragment.SETTINGS_SHOW_RASPI_BRICKS;
+import static org.catrobat.catroid.ui.settingsfragments.SettingsFragment.SETTINGS_SHOW_MQTT_BRICKS;
 import static org.hamcrest.Matchers.hasToString;
 import static org.hamcrest.Matchers.instanceOf;
 import static org.hamcrest.core.AllOf.allOf;
@@ -123,7 +124,7 @@ public class SettingsFragmentTest {
 			SETTINGS_CAST_GLOBALLY_ENABLED, SETTINGS_SHOW_AI_SPEECH_RECOGNITION_SENSORS,
 			SETTINGS_SHOW_AI_SPEECH_SYNTHETIZATION_SENSORS,
 			SETTINGS_SHOW_AI_FACE_DETECTION_SENSORS, SETTINGS_SHOW_AI_POSE_DETECTION_SENSORS,
-			SETTINGS_SHOW_AI_TEXT_RECOGNITION_SENSORS));
+			SETTINGS_SHOW_AI_TEXT_RECOGNITION_SENSORS, SETTINGS_SHOW_MQTT_BRICKS));
 	private Map<String, Boolean> initialSettings = new HashMap<>();
 	private Matcher<Intent> expectedBrowserIntent;
 
@@ -258,6 +259,15 @@ public void rasPiSettingsTest() {
 		checkPreference(R.string.preference_title_enable_raspi_bricks, SETTINGS_SHOW_RASPI_BRICKS);
 	}
 
+	@Category({Cat.AppUi.class, Level.Smoke.class, Cat.Gadgets.class})
+	@Test
+	public void mqttSettingsTest() {
+		onData(PreferenceMatchers.withTitle(R.string.preference_title_enable_mqtt_bricks))
+				.perform(click());
+
+		checkPreference(R.string.preference_title_enable_mqtt_bricks, SETTINGS_SHOW_MQTT_BRICKS);
+	}
+
 	@Category({Cat.AppUi.class, Level.Smoke.class, Cat.Gadgets.class})
 	@Test
 	public void aiSettingsTest() {

catroid/src/main/AndroidManifest.xml

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <!--
   ~ Catroid: An on-device visual programming system for Android devices
-  ~ Copyright (C) 2010-2025 The Catrobat Team
+  ~ Copyright (C) 2010-2026 The Catrobat Team
   ~ (<http://developer.catrobat.org/credits>)
   ~
   ~ This program is free software: you can redistribute it and/or modify

catroid/src/main/java/org/catrobat/catroid/ui/settingsfragments/MqttSettingsFragment.kt

@@ -0,0 +1,105 @@
+/*
+ * Catroid: An on-device visual programming system for Android devices
+ * Copyright (C) 2010-2026 The Catrobat Team
+ * (<http://developer.catrobat.org/credits>)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * An additional term exception under section 7 of the GNU Affero
+ * General Public License, version 3, is available at
+ * http://developer.catrobat.org/license_additional_term
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package org.catrobat.catroid.ui.settingsfragments
+
+import android.os.Bundle
+import android.preference.CheckBoxPreference
+import android.preference.EditTextPreference
+import android.preference.Preference
+import android.preference.PreferenceCategory
+import android.preference.PreferenceFragment
+import android.widget.Toast
+import androidx.annotation.VisibleForTesting
+import androidx.appcompat.app.AppCompatActivity
+import org.catrobat.catroid.R
+import org.catrobat.catroid.ui.settingsfragments.SettingsFragment.MQTT_CONNECTION_SETTINGS_CATEGORY
+import org.catrobat.catroid.ui.settingsfragments.SettingsFragment.MQTT_CLIENT_ID
+import org.catrobat.catroid.ui.settingsfragments.SettingsFragment.MQTT_HOST
+import org.catrobat.catroid.ui.settingsfragments.SettingsFragment.MQTT_PASSWORD
+import org.catrobat.catroid.ui.settingsfragments.SettingsFragment.MQTT_PORT
+import org.catrobat.catroid.ui.settingsfragments.SettingsFragment.MQTT_USERNAME
+import org.catrobat.catroid.ui.settingsfragments.SettingsFragment.SETTINGS_SHOW_MQTT_BRICKS
+
+class MqttSettingsFragment : PreferenceFragment() {
+
+    override fun onResume() {
+        super.onResume()
+        (activity as AppCompatActivity).supportActionBar?.title = preferenceScreen.title
+    }
+
+    override fun onActivityCreated(savedInstanceState: Bundle?) {
+        super.onActivityCreated(savedInstanceState)
+        SettingsFragment.setToChosenLanguage(activity)
+        addPreferencesFromResource(R.xml.mqtt_preferences)
+
+        val mqttCheckBoxPreference = findPreference(SETTINGS_SHOW_MQTT_BRICKS) as CheckBoxPreference
+        val mqttConnectionSettings = findPreference(MQTT_CONNECTION_SETTINGS_CATEGORY) as PreferenceCategory
+        mqttConnectionSettings.isEnabled = mqttCheckBoxPreference.isChecked
+
+        mqttCheckBoxPreference.onPreferenceChangeListener = Preference.OnPreferenceChangeListener { _, isChecked ->
+            mqttConnectionSettings.isEnabled = isChecked as Boolean
+            true
+        }
+
+        bindSummaryToValue(findPreference(MQTT_HOST) as EditTextPreference)
+        bindSummaryToValue(findPreference(MQTT_USERNAME) as EditTextPreference)
+        bindSummaryToValue(findPreference(MQTT_CLIENT_ID) as EditTextPreference)
+
+        val portPreference = findPreference(MQTT_PORT) as EditTextPreference
+        portPreference.summary = portPreference.text
+        portPreference.onPreferenceChangeListener = Preference.OnPreferenceChangeListener { _, newValue ->
+            if (!isValidPort(newValue.toString())) {
+                Toast.makeText(activity, R.string.preference_mqtt_port_invalid, Toast.LENGTH_SHORT).show()
+                return@OnPreferenceChangeListener false
+            }
+            portPreference.summary = newValue.toString()
+            true
+        }
+
+        val passwordPreference = findPreference(MQTT_PASSWORD) as EditTextPreference
+        passwordPreference.onPreferenceChangeListener = Preference.OnPreferenceChangeListener { _, _ -> true }
+    }
+
+    private fun bindSummaryToValue(preference: EditTextPreference) {
+        preference.summary = preference.text
+        preference.onPreferenceChangeListener = Preference.OnPreferenceChangeListener { pref, newValue ->
+            (pref as EditTextPreference).summary = newValue.toString()
+            true
+        }
+    }
+
+    companion object {
+        private const val MIN_PORT = 1
+        private const val MAX_PORT = 65_535
+
+        @JvmField val TAG: String = MqttSettingsFragment::class.java.simpleName
+
+        @VisibleForTesting
+        @JvmStatic
+        fun isValidPort(value: String): Boolean {
+            val port = value.toIntOrNull() ?: return false
+            return port in MIN_PORT..MAX_PORT
+        }
+    }
+}

catroid/src/main/java/org/catrobat/catroid/ui/settingsfragments/SettingsFragment.java

@@ -125,12 +125,21 @@ public class SettingsFragment extends PreferenceFragment {
 	public static final String DRONE_ROTATION_SPEED = "setting_drone_rotation_speed";
 	public static final String DRONE_TILT_ANGLE = "setting_drone_tilt_angle";
 
-
 	public static final String RASPI_CONNECTION_SETTINGS_CATEGORY = "setting_raspi_connection_settings_category";
 	public static final String RASPI_HOST = "setting_raspi_host_preference";
 	public static final String RASPI_PORT = "setting_raspi_port_preference";
 	public static final String RASPI_VERSION_SPINNER = "setting_raspi_version_preference";
 
+	public static final String MQTT_SCREEN_KEY = "settings_mqtt_screen";
+	public static final String SETTINGS_SHOW_MQTT_BRICKS = "setting_mqtt_bricks";
+	public static final String MQTT_CONNECTION_SETTINGS_CATEGORY = "setting_mqtt_category";
+	public static final String MQTT_HOST = "setting_mqtt_host";
+	public static final String MQTT_PORT = "setting_mqtt_port";
+	public static final String MQTT_TLS = "setting_mqtt_tls";
+	public static final String MQTT_USERNAME = "setting_mqtt_username";
+	public static final String MQTT_PASSWORD = "setting_mqtt_password";
+	public static final String MQTT_CLIENT_ID = "setting_mqtt_client_id";
+
 	public static final String SETTINGS_CRASH_REPORTS = "setting_enable_crash_reports";
 	public static final String TAG = SettingsFragment.class.getSimpleName();
 
@@ -210,6 +219,12 @@ public void onCreate(Bundle savedInstanceState) {
 			screen.removePreference(testPreference);
 		}
 
+		if (!BuildConfig.FEATURE_MQTT_ENABLED) {
+			PreferenceScreen mqttPreference = (PreferenceScreen) findPreference(MQTT_SCREEN_KEY);
+			mqttPreference.setEnabled(false);
+			screen.removePreference(mqttPreference);
+		}
+
 		setCorrectPreferenceViewForEmbroidery();
 		setCorrectPreferenceViewForPhiro();
 	}
@@ -262,6 +277,12 @@ public boolean onPreferenceTreeClick(PreferenceScreen preferenceScreen, Preferen
 						.addToBackStack(RaspberryPiSettingsFragment.TAG)
 						.commit();
 				break;
+			case MQTT_SCREEN_KEY:
+				getFragmentManager().beginTransaction()
+						.replace(R.id.content_frame, new MqttSettingsFragment(), MqttSettingsFragment.TAG)
+						.addToBackStack(MqttSettingsFragment.TAG)
+						.commit();
+				break;
 		}
 		return super.onPreferenceTreeClick(preferenceScreen, preference);
 	}
@@ -408,6 +429,38 @@ public static boolean isRaspiSharedPreferenceEnabled(Context context) {
 		return getBooleanSharedPreference(false, SETTINGS_SHOW_RASPI_BRICKS, context);
 	}
 
+	public static boolean isMqttSharedPreferenceEnabled(Context context) {
+		return getBooleanSharedPreference(false, SETTINGS_SHOW_MQTT_BRICKS, context);
+	}
+
+	public static String getMqttHost(Context context) {
+		return getSharedPreferences(context).getString(MQTT_HOST, context.getString(R.string.default_mqtt_host));
+	}
+
+	public static int getMqttPort(Context context) {
+		try {
+			return Integer.parseInt(getSharedPreferences(context).getString(MQTT_PORT, "1883"));
+		} catch (NumberFormatException e) {
+			return 1883;
+		}
+	}
+
+	public static boolean isMqttTlsEnabled(Context context) {
+		return getBooleanSharedPreference(false, MQTT_TLS, context);
+	}
+
+	public static String getMqttUsername(Context context) {
+		return getSharedPreferences(context).getString(MQTT_USERNAME, "");
+	}
+
+	public static String getMqttPassword(Context context) {
+		return getSharedPreferences(context).getString(MQTT_PASSWORD, "");
+	}
+
+	public static String getMqttClientId(Context context) {
+		return getSharedPreferences(context).getString(MQTT_CLIENT_ID, "");
+	}
+
 	public static boolean isNfcSharedPreferenceEnabled(Context context) {
 		return getBooleanSharedPreference(false, SETTINGS_SHOW_NFC_BRICKS, context);
 	}

catroid/src/main/res/values/strings.xml

@@ -1531,6 +1531,24 @@ needs read and write access to it. You can always change permissions through you
     <string formatted="false" name="error_connecting_to">Error: Could not connect to %s : %d</string>
     <!--  -->
 
+    <!-- MQTT Settings -->
+    <string formatted="false" name="preference_title_enable_mqtt_bricks">MQTT extension</string>
+    <string formatted="false" name="preference_description_mqtt_bricks">Allow the app to connect to MQTT brokers</string>
+    <string formatted="false" name="preference_title_mqtt_enabled">Enable MQTT bricks</string>
+    <string formatted="false" name="preference_description_mqtt_enabled">Enable bricks and sensors for MQTT</string>
+    <string formatted="false" name="preference_title_mqtt_category">MQTT settings</string>
+    <string formatted="false" name="preference_title_mqtt_broker_host">Broker host</string>
+    <string formatted="false" name="preference_description_mqtt_broker_host">IP address or hostname of the MQTT broker</string>
+    <string formatted="false" name="preference_title_mqtt_broker_port">Broker port</string>
+    <string formatted="false" name="preference_description_mqtt_broker_port">Port number of the MQTT broker (1–65535)</string>
+    <string formatted="false" name="preference_title_mqtt_use_tls">Use TLS</string>
+    <string formatted="false" name="preference_title_mqtt_username">Username</string>
+    <string formatted="false" name="preference_title_mqtt_password">Password</string>
+    <string formatted="false" name="preference_title_mqtt_client_id">Client ID</string>
+    <string formatted="false" name="preference_mqtt_port_invalid">Port must be a number between 1 and 65535</string>
+    <string name="default_mqtt_host" translatable="false">192.168.0.1</string>
+    <!--  -->
+
     <!-- Lego Mindstorms Strings -->
     <string formatted="false" name="nxt_brick_motor_move">Set NXT motor</string>
     <string formatted="false" name="nxt_motor_speed_to">to</string>

catroid/src/main/res/xml/mqtt_preferences.xml

@@ -0,0 +1,76 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  ~ Catroid: An on-device visual programming system for Android devices
+  ~ Copyright (C) 2010-2025 The Catrobat Team
+  ~ (<http://developer.catrobat.org/credits>)
+  ~
+  ~ This program is free software: you can redistribute it and/or modify
+  ~ it under the terms of the GNU Affero General Public License as
+  ~ published by the Free Software Foundation, either version 3 of the
+  ~ License, or (at your option) any later version.
+  ~
+  ~ An additional term exception under section 7 of the GNU Affero
+  ~ General Public License, version 3, is available at
+  ~ http://developer.catrobat.org/license_additional_term
+  ~
+  ~ This program is distributed in the hope that it will be useful,
+  ~ but WITHOUT ANY WARRANTY; without even the implied warranty of
+  ~ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+  ~ GNU Affero General Public License for more details.
+  ~
+  ~ You should have received a copy of the GNU Affero General Public License
+  ~ along with this program.  If not, see <http://www.gnu.org/licenses/>.
+  -->
+<PreferenceScreen
+    android:key="settings_mqtt_screen"
+    android:summary="@string/preference_description_mqtt_bricks"
+    android:title="@string/preference_title_enable_mqtt_bricks"
+    xmlns:android="http://schemas.android.com/apk/res/android">
+
+    <CheckBoxPreference
+        android:defaultValue="false"
+        android:key="setting_mqtt_bricks"
+        android:summary="@string/preference_description_mqtt_enabled"
+        android:title="@string/preference_title_mqtt_enabled" />
+
+    <PreferenceCategory
+        android:key="setting_mqtt_category"
+        android:title="@string/preference_title_mqtt_category">
+
+        <EditTextPreference
+            android:defaultValue="192.168.0.1"
+            android:key="setting_mqtt_host"
+            android:summary="@string/preference_description_mqtt_broker_host"
+            android:title="@string/preference_title_mqtt_broker_host" />
+
+        <EditTextPreference
+            android:defaultValue="1883"
+            android:inputType="number"
+            android:key="setting_mqtt_port"
+            android:summary="@string/preference_description_mqtt_broker_port"
+            android:title="@string/preference_title_mqtt_broker_port" />
+
+        <CheckBoxPreference
+            android:defaultValue="false"
+            android:key="setting_mqtt_tls"
+            android:title="@string/preference_title_mqtt_use_tls" />
+
+        <EditTextPreference
+            android:defaultValue=""
+            android:key="setting_mqtt_username"
+            android:title="@string/preference_title_mqtt_username" />
+
+        <EditTextPreference
+            android:defaultValue=""
+            android:inputType="textPassword"
+            android:key="setting_mqtt_password"
+            android:title="@string/preference_title_mqtt_password" />
+
+        <EditTextPreference
+            android:defaultValue=""
+            android:key="setting_mqtt_client_id"
+            android:title="@string/preference_title_mqtt_client_id" />
+
+    </PreferenceCategory>
+
+</PreferenceScreen>

catroid/src/main/res/xml/preferences.xml

@@ -104,6 +104,11 @@
         android:summary="@string/preference_description_raspi_bricks"
         android:title="@string/preference_title_enable_raspi_bricks" />
 
+    <PreferenceScreen
+        android:key="settings_mqtt_screen"
+        android:summary="@string/preference_description_mqtt_bricks"
+        android:title="@string/preference_title_enable_mqtt_bricks" />
+
     <Preference
         android:key="setting_enable_phiro_bricks_preference"
         android:summary="@string/preference_description_phiro_bricks"