This sample contains two separate Android applications: DragSource and DropTarget. DragSource contains images and text that can be dropped into the DropTarget app. Images are shared between the two apps through a URI for which the receiving app must request permission first, before it can be used.
It also demonstrates the use of the DragStartHelper from the v13 support library to easily handle drag and drop events.
Android N introduces support for drag and drop between applications, augmenting the existing APIs that have enabled this within a single window before.
To start a drag operation you need to call View.startDragAndDrop. Which gesture or action triggers this is up to you as an app developer. The API guide recommends doing this from View.OnLongClickListener.onLongClick and this seems to be the de-facto standard, but you are free to use other gestures (single tap, tap and drag etc). However, if you go for a unconventional drag start gesture, note that the framework implementation assumes that the pointer (touch or mouse) is down while the drag is starting, and the most recent touch/click position is used as the original position of the drag shadow.
See also android.support.v13.view.DragStartHelper which uses different gestures for touch and mouse (click and drag works better for mouse than a long click).
By default a drag and drop operation is constrained by the window containing the view that started the drag. To enable cross-window and cross-app drag and drop add View.DRAG_FLAG_GLOBAL to the flags passed to the View.startDragAndDrop call.
If a Uri requiring permission grants is being sent, then the android.view.View.DRAG_FLAG_GLOBAL_URI_READ and/or the android.view.View.DRAG_FLAG_GLOBAL_URI_WRITE flags must be used also. To access content URIs requiring permissions on the receiving side, the target app needs to request the android.view.DropPermissions from the activity via android.app.Activity.requestDropPermissions. This permission will stay either until the activity is alive, or until the release() method is called on the android.view.DropPermissions object.
This sample uses the Gradle build system. To build this project, use the “gradlew build” command or use “Import Project” in Android Studio.
If you've found an error in this sample, please file an issue: https://github.com/googlesamples/android-DragAndDropAcrossApps-new
Patches are encouraged, and may be submitted by forking this project and submitting a pull request through GitHub. Please see CONTRIBUTING.md for more details.
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