Interface ClipboardDataProvider

public interface ClipboardDataProvider

Produces a clipboard or drag-and-drop representation on demand, so a payload that is expensive to build is only built if something actually asks for it.

This is what makes "drag a file out of the application" workable. A drag that offers ClipboardContent#MIME_FILE has to name the file when the drag starts, but the drop may never happen -- the user may let go over nothing -- and the target may prefer a different representation entirely. Registering a provider with ClipboardContent#setDataProvider(java.lang.String, com.codename1.ui.ClipboardDataProvider) declares that the representation is available without paying for it up front; the bytes are written, or the temporary file created, at the moment the receiving application reads that MIME type.

A provider is invoked at most once per ClipboardContent and MIME type -- the result is cached -- and it may be invoked from a native drag or clipboard thread rather than the event dispatch thread, so it must not touch the user interface.

When it actually runs

On the desktop and on iOS the provider runs when a receiver reads that representation, so a drag the user abandons costs nothing. Android is the exception: startDragAndDrop takes a complete clip, and a clip carries text or a reference to a file that already exists, so every provider runs as the drag begins. A drag out of an iOS application resolves its file list at the same moment for a related reason -- the system needs the number of items the drag carries, and for a file drag that is the number of files.

So a provider should be cheap enough to run once per drag, and must not assume it will only run when its data is wanted.

  • Method Summary

    Modifier and Type
    Method
    Description
    Object
    getClipboardData(String mimeType)
    Produces the value for one representation.

  • Method Details

    • getClipboardData

      Object getClipboardData(String mimeType)

      Produces the value for one representation.

      Parameters
      • mimeType: the MIME type being requested, always one this provider was registered for
      Returns

      the value, normally a String, a String[] of file paths or a byte[], or null when the representation turned out to be unavailable