Pro Android 4

Chapter  28

Implementing Drag and Drop

In the last chapter, we covered touchscreens, the MotionEvent class, and gestures. You learned how to use touch to make things happen in your application. One area that we didn’t cover was drag and drop. On the surface, drag and drop seems like it should be fairly simple: touch an object on the screen, drag it across the screen (usually over some other object), and let go, and the application should take the appropriate action. In many computer operating systems, this is a common way to delete a file from the desktop; you just drag the file’s icon to the trash-bin icon, and the file gets deleted. In Android, you may have seen how to rearrange icons on the home screen by dragging them to new locations or ...