Scheduler, Gantt with resource leveling, and Material 3 date and time pickers

CodenameOne/src/com/codename1/scheduling/AbstractScheduleModel.java

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+/*
+ * Copyright (c) 2026, Codename One and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Codename One designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code 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 General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Codename One through http://www.codenameone.com/ if you
+ * need additional information or have any questions.
+ */
+package com.codename1.scheduling;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/// The listener list and the refusals every read-only model shares.
+///
+/// A subclass has to supply `getResources` and `getItems`. Every edit is
+/// refused until the matching method is overridden.
+public abstract class AbstractScheduleModel implements ScheduleModel {
+    private final List<ScheduleChangeListener> listeners = new ArrayList<ScheduleChangeListener>();
+
+    @Override
+    public void setVisibleRange(long from, long to) {
+    }
+
+    @Override
+    public boolean updateItem(ScheduleItem item, long start, long end, String resourceId) {
+        return false;
+    }
+
+    @Override
+    public ScheduleItem createItem(long start, long end, String resourceId) {
+        return null;
+    }
+
+    @Override
+    public boolean removeItem(ScheduleItem item) {
+        return false;
+    }
+
+    @Override
+    public void addChangeListener(ScheduleChangeListener l) {
+        if (l != null && !listeners.contains(l)) {
+            listeners.add(l);
+        }
+    }
+
+    @Override
+    public void removeChangeListener(ScheduleChangeListener l) {
+        listeners.remove(l);
+    }
+
+    /// Tells every listener the model changed.
+    protected void fireChanged() {
+        // A listener may remove itself while it is told.
+        for (int i = listeners.size() - 1; i >= 0; i--) {
+            if (i < listeners.size()) {
+                listeners.get(i).scheduleChanged(this);
+            }
+        }
+    }
+}