DragSortListView

News

Nov. 23, 2012: Hmmm, what's this? → Gittip :)

Nov. 17, 2012: Drag-Sort Demos app in Google Play Store!

Nov. 15, 2012: Smooth operation! Drops and removals are animated. Also, DragSortController now provides a convenience click-to-remove feature (see XML attrs and RemoveListener sections).

Nov. 11, 2012: Mavenized. Thanks to Andreas Schildbach (Goonie)!

Oct. 30, 2012: DragSortCursorAdapter class helps you reorder a Cursor-backed ListAdapter. Look at ResourceDragSortCursorAdapter and SimpleDragSortCursorAdapter as well in the API.

Oct. 19, 2012: Public API documentation is up at http://bauerca.github.com/drag-sort-listview.

Oct. 19, 2012: Refactoring rampage. Backward compatibility is slightly broken. New features make it worthwhile :) and include: total floating View customization, total control over drag start/stop, and a helper class implementing common patterns (long-press to drag, fling-to-remove, etc.). Thanks to Dan Hulme (orac) for getting all this rolling! Check out the extensively updated demos and usage section below.

Sept. 26, 2012: Drag-sorting is now animated! (optional, of course) Items slide around underneath the floating (dragged) View.

Overview

DragSortListView (DSLV) is an extension of the Android ListView that enables drag-and-drop reordering of list items. It is a major overhaul complete rewrite of the TouchInterceptor (TI) meant to give drag-sorting a polished feel. Some key features are:

1. Clean drag and drop (no visual glitches; I hope!)
2. Intuitive and smooth scrolling while dragging.
3. Support for heterogeneous item heights.
4. Public startDrag() and stopDrag() methods.
5. Public interface for customizing the floating View.

DragSortListView is useful for all kinds of prioritized lists: favorites, playlists, checklists, etc. Would love to hear about your use case or app by email. I hope you find it useful; and please, help me improve the thing!

Widget usage

Three major elements define the drag-sort process. Roughly, in order of importance, they are:

1. Data reordering. Drag-sorts reorder the data underlying your list. Since DSLV cannot know how you organize your data, the reordering must be performed by you using the provided Listener interfaces.
2. Drag start/stop. Drags are started and stopped by calling startDrag() and stopDrag() on your DSLV instance; but some help that is. The convenience class, DragSortController, provides all kinds of boiler-plate for common start/stop/remove drag patterns.
3. Floating View. The floating View appearance and behavior is controlled by an implementation of the FloatViewManager interface. With this, you can display any View you like as the floating View, and update its appearance/location on every touch event. The DragSortController helper class also implements this interface for convenience.

Number 1 is essential. As mentioned above, 2 and 3 can be handled by the DragSortController helper class. Keep reading, then head to the demo and start studying some examples.

XML layout declaration

DragSortListView can be declared in an XML layout file just like the ListView. Several example layout files are provided in the demo. The available attributes (in addition to the usual ListView attributes) are given below. Read each bullet as

• <xml attr>: (<datatype>, <default value>) <description>.

XML attributes

• collapsed_height: (dimension, 1px) Height of placeholder at original drag position. Cannot be zero.
• drag_scroll_start: (float, 0.3) Start of drag-scroll regions (defined by a fraction of the total DSLV height; i.e. between 0 and 1).
• max_drag_scroll_speed: (float, 0.5) Maximum drag-scroll speed for default linear drag-scroll profile. Units of pixels/millisecond.
• float_alpha: (float, 1.0) Transparency of floating View. Value from 0 to 1 where 1 is opaque.
• slide_shuffle_speed: (float, 0.7) Speed of shuffle animations underneath floating View. A value of 0 means a shuffle animation is always in progress, whereas a value of 1 means items snap from position to position without animation.
• drop_animation_duration: (int, 150) Drop animation smoothly centers the floating View over the drop slot before destroying it. Duration in milliseconds.
• remove_animation_duration: (int, 150) Remove animation smoothly collapses the empty slot when an item is removed. Duration in milliseconds.
• track_drag_sort: (bool, false) Debugging option; explained below.
• use_default_controller: (bool, true) Have DSLV create a DragSortController instance and pass the following xml attributes to it. If you set this to false, ignore the following attributes.
• float_background_color: (color, BLACK) Set the background color of the floating View when using the default DragSortController. Floating View in this case is a snapshot of the list item to be dragged.
• drag_handle_id: (id, 0) Android resource id that points to a child View of a list item (or the root View of the list item layout). This identifies the "drag handle," or the View within a list item that must be touched to start a drag-sort of that item. Required if drags are to be enabled using the default DragSortController.
• sort_enabled: (bool, true) Enable sorting of dragged item (disabling is useful when you only want item removal).
• drag_start_mode: (enum, "onDown") Sets the gesture for starting a drag.
  • "onDown": Drag starts when finger touches down on the drag handle.
  • "onDrag": Drag starts when finger touches down on drag handle and then drags (allows item clicks and long clicks).
  • "onLongPress": Drag starts on drag handle long press (allows item clicks).
• remove_enabled: (bool, false) Enable dragged item removal by one of the remove_mode options below.
• remove_mode: (enum, "flingRight") Sets the gesture for removing the dragged item.
  • "clickRemove": Click on item child View with id click_remove_id.
  • "flingRight": Fling to the right; get outta here!
  • "flingLeft": Fling to the left; sayonara sucker!
  • "slideRight": Floating View fades as you slide your finger to the right; lifting while faded removes item.
  • "slideLeft": Floating View fades as you slide your finger to the right; lifting while faded removes item.
• click_remove_id: (id, 0) Android resource id that points to a child View of a list item. When remove_mode="clickRemove" and remove_enabled="true", a click on this child View removes the containing item. This attr is used by DragSortController.

Listeners

DragSortListView is a ListView, and thus requires a ListAdapter to populate its items. Drag-sorting additionally implies a reordering of the items in the ListAdapter, achieved through callbacks to special Listener interfaces defined in DSLV. Listeners can be registered with DSLV in two ways:

1. Pass them individually to the set*Listener() methods
2. Implement the Listener interfaces you require in a custom ListAdapter; when DragSortListView.setAdapter() is called with your custom Adapter, DSLV detects which interfaces are implemented and calls the appropriate set*Listener() methods on itself with the provided ListAdapter as argument.

Each Listener interface is described below:

DragSortListView.DropListener

The DropListener interface has a single callback:

public void drop(int from, int to);

This is called upon completion of the drag-sort; i.e. when the floating View is dropped. The parameter from is the ListView item that was originally dragged, and to is the position where the item was dropped. This is an important callback; without a DropListener, DSLV is for all practical purposes useless.

For proper DSLV operation, this callback must perform a reordering of the data in your ListAdapter. For example, one often has a Cursor that pulls from a database and backs a CursorAdapter. The order of items in the Cursor is fixed; therefore, given drag-sorting, you must implement a mapping from Cursor positions to DSLV positions. This is commonly done within in a custom ListAdapter or CursorWrapper that implements the DropListener interface. See Issue #20 for a discussion of this. Update: Or simply use the DragSortCursorAdapter class!

DragSortListView.RemoveListener

As the TI did, DSLV provides gestures for removing the floating View (and its associated list item) from the list. Upon completion of a remove gesture, DSLV calls the RemoveListener method:

public void remove(int which);

The position which should be "removed" from your ListAdapter; i.e. the mapping from your data (e.g. in a Cursor) to your ListAdapter should henceforth neglect the item previously pointed to by which. Whether you actually remove the data or not is up to you.

Item removal can now happen outside of a drag event. The method DragSortListView.removeItem(int position) can be called at any time.

DragSortListView.DragListener

The callback in the DragListener is

public void drag(int from, int to);

This is called whenever the floating View hovers to a new potential drop position; to is the current potential drop position, and from is the previous one. The TI provided this callback; an example of usage does not come to mind.

DragSortListView.DragSortListener

This is a convenience interface which combines all of the above Listener interfaces.

FloatViewManager

This is the interface that handles creation, updates, and tear-downs of the floating View. It is passed to DSLV using the setFloatViewManager() method. Example usage can be found in the SimpleFloatViewManager, which is a convenience class that simply takes a snapshot of the list item to be dragged.

If you want to spice up the floating View, implement your own FloatViewManager. In your onCreateFloatView() method, you should make sure that the View you return has a definite height (do not use MATCH_PARENT! although MATCH_PARENT is perfectly okay for the layout width). DSLV will measure and layout your floating View according to the ViewGroup.LayoutParams attached to it. If no LayoutParams are attached, DSLV will use WRAP_CONTENT and MATCH_PARENT as the layout height and width.

Drag start/stop

As of DragSortListView 0.3.0, drag start and stop behavior is all up to you. Feel free to call startDrag() or stopDrag() on the DSLV instance whenever you please. Be aware that if no touch event is in progress when startDrag() is called, the drag will not start. But don't waste too much time working on your own drag initiation if it's simple; the DragSortController described below will do that for you.

DragSortController

The DragSortController is a convenience class that implements some common design patterns for initiating drags or removing the dragged item from the list. It implements the View.OnTouchListener interface to watch touch events as they are dispatched to DSLV. It also implements the FloatViewManager interface (by subclassing SimpleFloatViewManager) to handle simple floating View creation. If you do not use XML to create the default DragSortController, you must pass in your own instance of DragSortController to both the setFloatViewManager() and setOnTouchListener() methods of the DSLV instance.

The default behavior of the DragSortController expects list items that are drag enabled to have a child View called a "drag handle." The drag handle View should have an associated android resource id, and that id should be passed into the DragSortController (the id can be set in XML if use_default_controller is true). If a touch event lands on the drag handle of an item, and a gesture is detected that should start a drag, the drag starts.

Additional documentation

There is limited documentation in the DSLV. You can check it out with Javadoc by navigating to /path/to/drag-sort-listview/src/ and typing

javadoc com.mobeta.android.dslv *

The javadoc can be viewed on the DSLV project page: http://bauerca.github.com/drag-sort-listview. Sorry for the many broken links at the moment. I am slowly getting to this.

Installation

Download and install the Android sdk. Clone/Download/Fork the repo through GitHub or via (read-only)

git clone https://github.com/bauerca/drag-sort-listview.git

Ant

Execute the following in both the drag-sort-listview/library/ and drag-sort-listview/demo/ directories (assuming /path/to/android_sdk/tools is in your PATH):

android update project --path ./

To test out the demo, navigate to drag-sort-listview/demo/ and execute

ant debug install

to build and install the demo on your connected device/emulator.

Maven

A simple

mvn clean install

should suffice to build and put the DSLV lib and demo in your local maven repository. To include in your project, add the following dependency to your pom.xml:

<dependency>
    <groupId>com.mobeta.android.dslv</groupId>
    <artifactId>drag-sort-listview</artifactId>
    <version>0.3.0-SNAPSHOT</version>
    <type>apklib</type>
</dependency>

Installation in Eclipse (Indigo)

The first step is to choose File > Import or right-click in the Project Explorer and choose Import. If you don't use E-Git to integrate Eclipse with Git, skip the rest of this paragraph. Choose "Projects from Git" as the import source. From the Git page, click Clone, and enter the URI of this repository. That's the only text box to fill in on that page. On the following pages, choose which branches to clone (probably all of them) and where to keep the local checkout, and then click Finish. Once the clone has finished, pick your new repository from the list, and on the following page select 'Use the New Projects wizard'.

From here the process is the same even if you don't use E-Git. Choose 'Android Project from Existing Code' and then browse to where you checked out DSLV. You should then see two projects in the list: one named after the directory name, and the other called com.mobeta.android.demodslv.Launcher . The top one is the library project, and the bottom one the demo project. You probably want both at first, so just click Finish.

Finally, to add the library to your application project, right-click your project in the Package Explorer and select Properties. Pick the "Android" page, and click "Add..." from the bottom half. You should see a list including the DSLV project as well as any others in your workspace.

Debugging

If you have python and matplotlib installed, you can use the script dslv.py to debug drag-sort behavior. This script is found in the project tools/ directory.

To enable, just set the dslv:track_drag_sort attribute to "true" in XML. While drag-sorting on your emulator or device, this tracking causes the DSLV to periodically dump its state to a file called dslv_state.txt in the device/emulator /sdcard/ directory.

Navigate to the location of dslv.py, and do

adb [-e|-d|-s device] pull /sdcard/dslv_state.txt

then simply run

python dslv.py

An image should appear that represents the DSLV in the final recorded state. Right and left keys allow stepping through the recorded drag-sort frame-by-frame; up/down keys jump 30 frames. This tool has been very useful for debugging jumpy behavior while drag-scrolling.

License

A subclass of the Android ListView component that enables drag
and drop re-ordering of list items.

Copyright 2012 Carl Bauer

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.