Migrate to null safety

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Changelog
 
+## Version 2.0.0 (2021-03-06)
+
+- Migrate to null safety.
+
 ## Version 1.4.3 (2019-12-10)
 
 - Remove unnecessary new keyword.

README.md

@@ -163,7 +163,7 @@ a `dnd-retarget` attribute to the host:
 
 The _Dart Drag and Drop_ library is inspired by
 
-- [jQuery UI Draggable](http://jqueryui.com/draggable/)
+- [jQuery UI Draggable](https://jqueryui.com/draggable/)
 - [Draggabilly](https://draggabilly.desandro.com/)
 
 Thank you for your work!

example/custom_acceptor/example.dart

@@ -31,7 +31,8 @@ class MyAcceptor extends Acceptor {
   @override
   bool accepts(
       Element draggableElement, int draggableId, Element dropzoneElement) {
-    InputElement input = draggableElement.querySelector('input');
+    InputElement? input =
+        draggableElement.querySelector('input') as InputElement?;
     return input != null && input.value == 'acceptme';
   }
 }

example/custom_avatar/example.dart

@@ -13,7 +13,7 @@ main() {
       avatarHandler: MyAvatarHandler());
 
   // Install dropzone (trash).
-  Element trash = querySelector('.trash');
+  Element trash = querySelector('.trash') as Element;
   Dropzone dropzone = Dropzone(trash);
 
   // Keep track if we're over the trash.
@@ -27,7 +27,7 @@ main() {
 
   // Change the drag avatar during the drag.
   draggable.onDrag.listen((DraggableEvent event) {
-    MyAvatarHandler handler = event.avatarHandler;
+    MyAvatarHandler handler = event.avatarHandler as MyAvatarHandler;
 
     if (overTrash) {
       // Set to last image if over trash.
@@ -79,10 +79,10 @@ class MyAvatarHandler extends AvatarHandler {
     setLeftTop(startPosition + OFFSET);
 
     // Ensure avatar has an absolute position.
-    avatar.style.position = 'absolute';
+    avatar!.style.position = 'absolute';
 
     // Add the drag avatar to the body element.
-    document.body.append(avatar);
+    document.body!.append(avatar!);
   }
 
   @override
@@ -92,7 +92,9 @@ class MyAvatarHandler extends AvatarHandler {
 
   @override
   void dragEnd(Point startPosition, Point position) {
-    avatar.remove();
+    if (avatar != null) {
+      avatar!.remove();
+    }
   }
 
   /// Updates the image to [imageNumber].

example/detection_only/example.dart

@@ -10,7 +10,7 @@ main() {
   Draggable draggable = Draggable(querySelector('.draggable'));
 
   // Paragraph.
-  Element p = querySelector('.draggable p');
+  Element p = querySelector('.draggable p') as Element;
 
   // Listen to drag start.
   draggable.onDragStart.listen((DraggableEvent event) {

example/nested_dropzones/example.dart

@@ -15,9 +15,9 @@ main() {
   Dropzone innerDropzone = Dropzone(querySelector('.dropzone-inner'));
 
   // The text elements.
-  Element draggableText = querySelector('.draggable > p');
-  Element outerText = querySelector('.dropzone-outer > span');
-  Element innerText = querySelector('.dropzone-inner > span');
+  Element draggableText = querySelector('.draggable > p') as Element;
+  Element outerText = querySelector('.dropzone-outer > span') as Element;
+  Element innerText = querySelector('.dropzone-inner > span') as Element;
 
   // Dropped flags to help for displaying the correct text in dragLeave
   // (dragLeave is fired after a drop).

example/nested_elements/example.dart

@@ -12,7 +12,7 @@ main() {
   Dropzone dropzone = Dropzone(querySelector('.dropzone'));
 
   // Text element
-  Element text = querySelector('.dropzone > span');
+  Element text = querySelector('.dropzone > span') as Element;
 
   // Listen to dragEnter.
   dropzone.onDragEnter.listen((DropzoneEvent event) {

example/simple_sortable/example.dart

@@ -18,9 +18,9 @@ main() {
 
 /// Simple function to swap two elements.
 void swapElements(Element elm1, Element elm2) {
-  var parent1 = elm1.parent;
+  var parent1 = elm1.parent as Element;
   var next1 = elm1.nextElementSibling;
-  var parent2 = elm2.parent;
+  var parent2 = elm2.parent as Element;
   var next2 = elm2.nextElementSibling;
 
   parent1.insertBefore(elm2, next1);

lib/src/draggable.dart

@@ -4,7 +4,7 @@ part of dnd;
 /// all [Draggable]s know when a drag operation is already handled.
 /// Is also used by the [Dropzone] because we can't pass an [Element] through
 /// the [CustomEvent]s.
-_DragInfo _currentDrag;
+_DragInfo? _currentDrag;
 
 /// The [Draggable] detects drag operations for touch and mouse interactions and
 /// optionally creates a drag avatar for visual feedback of the drag. Event
@@ -27,7 +27,7 @@ class Draggable {
   // --------------
   /// [avatarHandler] is a function to create a [DragAvatar] for this [Draggable].
   /// See [Draggable] constructor.
-  AvatarHandler avatarHandler;
+  AvatarHandler? avatarHandler;
 
   /// When set to true, only horizontal dragging is tracked. This enables
   /// vertical touch dragging to be used for scrolling.
@@ -39,7 +39,7 @@ class Draggable {
 
   /// Restricts dragging from starting to the [handle].
   /// See [Draggable] constructor.
-  String handle;
+  String? handle;
 
   /// Prevents dragging from starting on specified elements.
   /// See [Draggable] constructor.
@@ -60,7 +60,7 @@ class Draggable {
   /// The minimum distance for a drag to prevent click events.
   /// DEPRECATED: Please use [minDragStartDistance] instead.
   @deprecated
-  get clickSuppression => minDragStartDistance;
+  int get clickSuppression => minDragStartDistance;
 
   /// DEPRECATED: Please use [minDragStartDistance] instead.
   @deprecated
@@ -69,9 +69,9 @@ class Draggable {
   // -------------------
   // Events
   // -------------------
-  StreamController<DraggableEvent> _onDragStart;
-  StreamController<DraggableEvent> _onDrag;
-  StreamController<DraggableEvent> _onDragEnd;
+  StreamController<DraggableEvent>? _onDragStart;
+  StreamController<DraggableEvent>? _onDrag;
+  StreamController<DraggableEvent>? _onDragEnd;
 
   /// Fired when the user starts dragging.
   ///
@@ -83,7 +83,7 @@ class Draggable {
       _onDragStart = StreamController<DraggableEvent>.broadcast(
           sync: true, onCancel: () => _onDragStart = null);
     }
-    return _onDragStart.stream;
+    return _onDragStart!.stream;
   }
 
   /// Fired periodically throughout the drag operation.
@@ -92,7 +92,7 @@ class Draggable {
       _onDrag = StreamController<DraggableEvent>.broadcast(
           sync: true, onCancel: () => _onDrag = null);
     }
-    return _onDrag.stream;
+    return _onDrag!.stream;
   }
 
   /// Fired when the user ends the dragging.
@@ -102,12 +102,12 @@ class Draggable {
       _onDragEnd = StreamController<DraggableEvent>.broadcast(
           sync: true, onCancel: () => _onDragEnd = null);
     }
-    return _onDragEnd.stream;
+    return _onDragEnd!.stream;
   }
 
   /// Abort the current drag
   void abort() {
-    if (_currentDrag != null && _currentDrag.draggableId == this.id) {
+    if (_currentDrag != null && _currentDrag!.draggableId == this.id) {
       _handleDragEnd(null, null, cancelled: true);
     }
   }
@@ -116,7 +116,7 @@ class Draggable {
   // Private Properties
   // -------------------
   /// The list of [Element]s on which a drag is detected.
-  List<Element> _elements;
+  late List<Element> _elements;
 
   /// Managers for browser events.
   final List<_EventManager> _eventManagers = [];
@@ -172,7 +172,7 @@ class Draggable {
       this.draggingClassBody = 'dnd-drag-occurring',
       this.minDragStartDistance = 4}) {
     // Wrap in a List if it is not a list but a single Element.
-    _elements = elementOrElementList is List
+    _elements = elementOrElementList is List<Element>
         ? elementOrElementList
         : [elementOrElementList];
 
@@ -194,29 +194,25 @@ class Draggable {
 
   /// Handles the drag start. The [moveEvent] might either be a
   /// [TouchEvent] or a [MouseEvent].
-  void _handleDragStart(UIEvent moveEvent) {
+  void _handleDragStart(Event moveEvent) {
     // Set the drag started flag.
-    _currentDrag.started = true;
+    _currentDrag!.started = true;
 
     // Pass event to AvatarHandler.
     if (avatarHandler != null) {
-      avatarHandler._handleDragStart(
-          _currentDrag.element, _currentDrag.position);
+      avatarHandler!
+          ._handleDragStart(_currentDrag!.element, _currentDrag!.position);
     }
 
     // Fire the drag start event with start position.
     if (_onDragStart != null) {
       // The dragStart has the same for startPosition and current position.
-      _onDragStart.add(DraggableEvent._(moveEvent, _currentDrag));
+      _onDragStart!.add(DraggableEvent._(moveEvent, _currentDrag!));
     }
 
     // Add the css classes during the drag operation.
-    if (draggingClass != null) {
-      _currentDrag.element.classes.add(draggingClass);
-    }
-    if (draggingClassBody != null) {
-      document.body.classes.add(draggingClassBody);
-    }
+    _currentDrag!.element.classes.add(draggingClass);
+    document.body!.classes.add(draggingClassBody);
 
     // Text selections should not be a problem, but it seems better usability
     // to remove text selection when dragging something.
@@ -227,19 +223,19 @@ class Draggable {
   /// [MouseEvent].
   ///
   /// The [target] is the actual target receiving the event.
-  void _handleDrag(UIEvent moveEvent, EventTarget target) {
+  void _handleDrag(Event moveEvent, EventTarget? target) {
     // Pass event to AvatarHandler.
     if (avatarHandler != null) {
-      avatarHandler._handleDrag(
-          _currentDrag.startPosition, _currentDrag.position);
+      avatarHandler!
+          ._handleDrag(_currentDrag!.startPosition, _currentDrag!.position);
     }
 
     // Dispatch internal drag enter, over, or leave event.
     _DragEventDispatcher.dispatchEnterOverLeave(this, target);
 
     // Fire the drag event.
     if (_onDrag != null) {
-      _onDrag.add(DraggableEvent._(moveEvent, _currentDrag));
+      _onDrag!.add(DraggableEvent._(moveEvent, _currentDrag!));
     }
   }
 
@@ -252,13 +248,13 @@ class Draggable {
   ///
   /// Set [cancelled] to true to indicate that this drag ended through a
   /// cancel oparation like hitting the `esc` key.
-  void _handleDragEnd(Event event, EventTarget target, {cancelled = false}) {
+  void _handleDragEnd(Event? event, EventTarget? target, {cancelled = false}) {
     // Only handle drag end if the user actually did drag and not just clicked.
-    if (_currentDrag.started) {
+    if (_currentDrag != null && _currentDrag!.started) {
       // Pass event to AvatarHandler.
       if (avatarHandler != null) {
-        avatarHandler._handleDragEnd(
-            _currentDrag.startPosition, _currentDrag.position);
+        avatarHandler!._handleDragEnd(
+            _currentDrag!.startPosition, _currentDrag!.position);
       }
 
       // Dispatch internal drop event if drag was not cancelled.
@@ -268,8 +264,8 @@ class Draggable {
 
       // Fire dragEnd event.
       if (_onDragEnd != null) {
-        _onDragEnd
-            .add(DraggableEvent._(event, _currentDrag, cancelled: cancelled));
+        _onDragEnd!
+            .add(DraggableEvent._(event, _currentDrag!, cancelled: cancelled));
       }
 
       // Prevent TouchEvent from emulating a click after touchEnd event.
@@ -279,16 +275,12 @@ class Draggable {
 
       // Prevent MouseEvent from firing a click after mouseUp event.
       if (event is MouseEvent) {
-        _suppressClickEvent(_currentDrag.element);
+        _suppressClickEvent(_currentDrag!.element);
       }
 
       // Remove the css classes.
-      if (draggingClass != null) {
-        _currentDrag.element.classes.remove(draggingClass);
-      }
-      if (draggingClassBody != null) {
-        document.body.classes.remove(draggingClassBody);
-      }
+      _currentDrag!.element.classes.remove(draggingClass);
+      document.body!.classes.remove(draggingClassBody);
     }
 
     // Reset.
@@ -320,8 +312,8 @@ class Draggable {
     // Destroy all managers with their listeners.
     _eventManagers.forEach((m) => m.destroy());
     _eventManagers.clear();
-    if (avatarHandler != null && avatarHandler.avatar != null) {
-      avatarHandler.avatar.remove();
+    if (avatarHandler != null && avatarHandler!.avatar != null) {
+      avatarHandler!.avatar!.remove();
     }
   }
 
@@ -341,7 +333,7 @@ class Draggable {
   /// in active textarea or active input element.
   void _clearTextSelections() {
     // Remove selection.
-    window.getSelection().removeAllRanges();
+    window.getSelection()?.removeAllRanges();
 
     // Try to remove selection from textarea or input.
     try {
@@ -364,15 +356,15 @@ class DraggableEvent {
   final Element draggableElement;
 
   /// The [AvatarHandler] or null if there is none.
-  final AvatarHandler avatarHandler;
+  final AvatarHandler? avatarHandler;
 
   /// The original event which is either ...
   /// * a [MouseEvent],
   /// * a [TouchEvent],
   /// * a [KeyboardEvent] when the user clicks the esc-key,
   /// * a normal [Event] when the window loses focus (blur event), or
   /// * null if the drag was programmatically aborted.
-  final Event originalEvent;
+  final Event? originalEvent;
 
   /// Position where the drag started, relative to the whole document (page
   /// position).
@@ -408,11 +400,11 @@ class _DragInfo {
   final Point startPosition;
 
   /// The [AvatarHandler] or null if there is none.
-  final AvatarHandler avatarHandler;
+  final AvatarHandler? avatarHandler;
 
   /// The current position of the mouse or touch. This position is constrained
   /// by the horizontal/vertical axis.
-  Point _position;
+  late Point _position;
 
   /// Flag indicating if the drag started.
   bool started = false;