Dart Drag and Drop #
Drag and Drop for Dart web apps with mouse and touch support.
- Use any HTML Element as
- Mouse and Touch dragging.
- Draggable events:
- Dropzone events:
- Drag avatars as visual indication of a drag operation:
- Original element as drag avatar.
- Clone as drag avatar.
- Custom drag avatar.
- Support for Shadow DOM (Web Components, Custom Elements, Polymer, etc.).
- Much more... see examples.
Before you read the instructions below, you should take a look at the examples.
Basic Set Up #
Draggable and give it some HTML elements; this will make them
draggable. You can either pass a single
Element to the constructor or an
ElementList that is returned by
If you also want to drop somewhere, you'll need a
// Install draggable (no avatar). Draggable draggable = new Draggable(querySelectorAll('.draggable')); // Install dropzone. Dropzone dropzone = new Dropzone(querySelector('.dropzone'));
You'll most likely want some drag avatar to show the user that a drag is
going on. There are two predefined
AvatarHandlers that you can use as follows.
But you could also provide your own implementation of
// Draggable with clone as avatar. Draggable draggable = new Draggable(querySelectorAll('.draggable'), avatarHandler: new AvatarHandler.clone()); // Draggable with original element as avatar. Draggable draggable = new Draggable(querySelectorAll('.draggable'), avatarHandler: new AvatarHandler.original());
Draggable Options #
The following options can be passed as named parameters to the constructor of
avatarHandler: Is responsible for creating, position, and removing a drag avatar. A drag avatar provides visual feedback during a drag operation. Here are possible options (see above for an example):
null(the default) - will not create a drag avatar
new AvatarHandler.original()- handler that uses the original draggable as avatar. See
new AvatarHandler.clone()- handler that uses a clone of the draggable element as avatar. See
- A custom
AvatarHandler- you can provide your own implementation of
horizontalOnly: If set to true, only horizontal dragging is tracked. This enables vertical touch dragging to be used for scrolling.
verticalOnly: If set to true, only vertical dragging is tracked. This enables horizontal touch dragging to be used for scrolling.
handle: If handle query String is specified, it restricts the dragging from starting unless it occurs on the specified element(s). Only elements that descend from the draggables elements are permitted.
cancel: If cancel query String is specified, drag starting is prevented on specified elements.
draggingClass: Is the css class set to the dragged element during a drag. If set to null, no such css class is added.
draggingClassBody: Is the css class set to the html body tag during a drag. If set to null, no such css class is added.
minDragStartDistance: Is the minimum distance in pixels that is needed for a drag to start. Default is
4. This allows for clicks with tiny movement.
Draggable Events #
onDragStart: Fired when the user starts dragging.
onDragStartis fired not on touchStart or mouseDown but as soon as there is a drag movement. When a drag is started an
onDragevent will also be fired.
onDrag: Fired periodically throughout the drag operation.
onDragEnd: Fired when the user ends the dragging.
Note: Is also fired when the user clicks the 'esc'-key or the window loses focus.
Dropzone Options #
The following options can be passed as named parameters to the constructor of
acceptor: Is used to determine which
Draggables will be accepted by this
Dropzone. If none is specified, all
Draggables will be accepted.
overClass: Is the css class set to the dropzone element when an accepted draggable is dragged over it. If set to null, no such css class is added.
invalidClass: Is the css class set to the dropzone element when a not-accepted draggable is dragged over it. If set to null, no such css class is added.
Dropzone Events #
onDragEnter: Fired when a
onDragOver: Fired periodically while a
Draggableis moved over a
onDragLeave: Fired when a
onDrop: Fired when a
Draggableis dropped inside this
Dropzone events are only fired when the
Draggable is accepted by
Shadow DOM #
Web Components create a nice ecapsulation through Shadow DOM. But this creates
a problem with dropzones inside the Shadow DOM as they never receive events
because all events are captured by the host element. To make this work we need
to retarget events to the Shadow DOM children through recursive
For performance reasons it wouldn't make sense to retarget all drag and drop
events. If you wish to retarget events to the Shadow DOM children, you must add
dnd-retarget attribute to the host:
// Retarget drag and drop events to Shadow DOM children. <my-element dnd-retarget></my-element>
The Dart Drag and Drop library is inspired by
Thank you for your work!
The MIT License (MIT)
Version 1.4.2 (2019-02-13) #
- Fix #30: Cannot initialize Dropzone with List
- Follow more code style conventions.
- Update dependencies.
Version 1.4.0 (2018-10-12) #
- Add an option
Draggableto define the minimum distance in pixels that is needed for a drag to start (#26). Default is
4pixels. This allows for clicks with tiny movement. The option
clickSuppressionhas been marked as DEPRECATED as it had the same goal but a misleading name.
Version 1.3.0 (2018-08-15) #
- Align dart version to support Dart 2 (#25).
Version 1.2.0 (2018-06-21) #
- Support for creating a Draggable with
List<Element>(in addition to
Version 1.1.0 (2018-06-21) #
- Remove cursor files. Support for
-webkit-grabbingis good enough.
Version 1.0.0 (2018-06-13) #
- Migrate to Dart 2.
- Since Chrome 56 touch event listeners are treated as passive by default. This disables the possibility to call
preventDefaulton an element which we must do to tell the browser not to scroll while dragging. To fix this in Chrome we set the
touch-actioncss property. With this Chrome will not scroll (
none) or only scroll in one direction (
Version 0.4.0 (2017-06-27) #
- Fix strong mode errors (#20).
Version 0.3.6 (2017-06-06) #
- Fix bug: Provide reasonable fallback for event target when mouse position exits viewport (#19).
Version 0.3.5 (2016-11-22) #
- Handle the edge case where destroy is called while dragging an avatar (#17).
Version 0.3.4 (2016-10-19) #
- Fix strong-mode type errors (#15).
- Remove Shadow DOM example and (dev)dependency on Polymer (was causing some confusion).
Version 0.3.3 (2016-09-22) #
- Allow a configurable clickSuppression distance (#13). We found that the click suppression was a little too aggressive for users with less mousing accuracy. They would attempt to click and trigger a small drag. Which then suppressed the click event and prevented the action they intended to complete.
Version 0.3.2 (2016-07-26) #
- Remove null-aware operator since drone.io uses an old version of Dart that doesn't support this yet.
Version 0.3.1 (2016-07-26) #
- Support for programmatic drag abort (see issue #11).
Version 0.3.0 (2015-04-18) #
- BREAKING CHANGE: Refactoring the
AvatarHandler. Only if you've implemented a custom
AvatarHandleryou might need to do some changes:
resetPointerEventswere removed and don't need to be called any more. Pointer event styles are handled automatically.
AvatarHandlermargin caching: The
AvatarHandleronly cached the margins once for every
Draggable. This caused problems when margins of elements in the same
Draggablehad different margins or the margins were changed. Now the margins are reset after every drag.
Version 0.2.1 (2015-03-09) #
- Fix #9: Using transformers in the main
pubspec.yamlcaused problems with projects depending on the
Version 0.2.0 (2015-03-09) #
- Fix #3: Shadow DOM is now supported. A
dnd-retargetattribute must be added to all custom elements where events should be forwarded to the Shadow DOM children.
- Fix #7: Add a css class (
dnd-invalidby default) to dropzones when a not-accepted draggable is dragged over.
Version 0.1.4 (2014-10-20) #
- Add a sortable example.
- Change comments according to new Dart Style Guide rule
- Move event dispatching calls from EventManager to Draggable (refactoring).
Version 0.1.3 (2014-08-09) #
- Fix #4: Problem when an ancestor of the dragged element was positioned (relative, absolute, fixed).
Version 0.1.2 (2014-07-22) #
- Correcting small bug that occurred when setSelectionRange() was called on an element that does not support it.
- Fix Pointer Event bug: Too many event listeners in move, end, cancel.
- Fix for Bug #1 - Not working in Windows 8.1 IE11
- Adding a
DraggableEventto indicate if a drag ended because of a cancelling operation like
Version 0.1.1 (2014-07-21) #
- Support for IE10 and IE11 touch screens through pointer events.
disableMouseoptions. The goal was to unify touch and mouse dragging, so it should not be necessary to disable one or the other.
Version 0.1.0 (2014-07-17) #
- First version.
index.html is an overview of the examples in the subfolders.
Use this package as a library
1. Depend on it
Add this to your package's pubspec.yaml file:
dependencies: dnd: ^1.4.2
2. Install it
You can install packages from the command line:
$ pub get
Alternatively, your editor might support
Check the docs for your editor to learn more.
3. Import it
Now in your Dart code, you can use:
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We analyzed this package on Nov 11, 2019, and provided a score, details, and suggestions below. Analysis was completed with status completed using:
- Dart: 2.6.0
- pana: 0.12.21
Detected platforms: web
lib/src/draggable.dart. (-6.31 points)
lib/src/draggable.dart reported 13 hints, including:
line 83 col 22: Unnecessary new keyword.
line 92 col 17: Unnecessary new keyword.
line 102 col 20: Unnecessary new keyword.
line 180 col 25: Unnecessary new keyword.
line 184 col 26: Unnecessary new keyword.
lib/src/draggable_dispatch.dart. (-4.89 points)
lib/src/draggable_dispatch.dart reported 10 hints, including:
line 23 col 7: Unnecessary new keyword.
line 27 col 7: Unnecessary new keyword.
line 32 col 7: Unnecessary new keyword.
line 36 col 7: Unnecessary new keyword.
line 54 col 34: Unnecessary new keyword.
lib/src/dropzone.dart. (-3.93 points)
lib/src/dropzone.dart reported 8 hints, including:
line 42 col 22: Unnecessary new keyword.
line 51 col 21: Unnecessary new keyword.
line 60 col 22: Unnecessary new keyword.
line 70 col 17: Unnecessary new keyword.
line 146 col 18: Unnecessary new keyword.
Fix additional 3 files with analysis or formatting issues. (-2.99 points)
Additional issues in the following files: