Using Android Drag and Drop framework in My custom Launcher app

Question

I am trying to develop custom launcher app (with unlimited number of home pages)and i need to implement Drag and Drop as done in Launcher2(android 4.2).

So i found two approaches

1) Drag and Drop framework
2) Use the android launcher2 way like implementation DragController, DragSource as explained here.

But i am struggling to understand why didn't Android guys didn't use the Drag and Drop framework developed by them in their own application. Can anyone brief regarding possible rationale behind their approach?( i mean in terms of memory/performance)

Thanks in advance.

Answer 1

The Android drag and drop framework is very basic as compared to the one used in the Launcher app.

The Launcher app has a myriad of "layers" and the drag and drop occurs accross these layers, namely the DragLayer, Workspace and the All Apps view etc. It uses window flags and dynamically adds/removes views to the DragLayer when a drag is in progress and a multitude of activities monitor the drag. For more details look at the DragLayer.java and Workspace.java files particularly.

Answer 2

Drag and Drop in Android Launcher is done as Overlay drawing within the same ViewGroup and in same window . But android drag and drop approach creates a separate window with a separate window type altogether .

Resource and memory wise standard android drag and drop approach is costlier.

If performance is very critical my suggestion is go as per Android launcher way else prefer standard android approach its easy and simple.