TransferHandler.TransferSupport (Java Platform SE 8 )
Keywords: javax.swing.TransferHandler.TransferSupport class
Date: 2020-03-26

javax.swing

## Class TransferHandler.TransferSupport

- java.lang.Object
- - javax.swing.TransferHandler.TransferSupport

- Enclosing class:
    TransferHandler

      public static final class TransferHandler.TransferSupport
      extends Object

  This class encapsulates all relevant details of a clipboard or drag and drop transfer, and also allows for customizing aspects of the drag and drop experience.

  The main purpose of this class is to provide the information needed by a developer to determine the suitability of a transfer or to import the data contained within. But it also doubles as a controller for customizing properties during drag and drop, such as whether or not to show the drop location, and which drop action to use.

  Developers typically need not create instances of this class. Instead, they are something provided by the DnD implementation to certain methods in `TransferHandler`.

  Since:
    1.6
  See Also:
    `TransferHandler.canImport(TransferHandler.TransferSupport)`, `TransferHandler.importData(TransferHandler.TransferSupport)`

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `TransferSupport(Component component, Transferable transferable)` Create a `TransferSupport` with `isDrop()` `false` for the given component and `Transferable`.

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `Component` | `getComponent()` Returns the target component of this transfer.
    `DataFlavor[]` | `getDataFlavors()` Returns the data flavors for this transfer.
    `int` | `getDropAction()` Returns the action chosen for the drop, when this `TransferSupport` represents a drop.
    `TransferHandler.DropLocation` | `getDropLocation()` Returns the current (non-`null`) drop location for the component, when this `TransferSupport` represents a drop.
    `int` | `getSourceDropActions()` Returns the drag source's supported drop actions, when this `TransferSupport` represents a drop.
    `Transferable` | `getTransferable()` Returns the `Transferable` associated with this transfer.
    `int` | `getUserDropAction()` Returns the user drop action for the drop, when this `TransferSupport` represents a drop.
    `boolean` | `isDataFlavorSupported(DataFlavor df)` Returns whether or not the given data flavor is supported.
    `boolean` | `isDrop()` Returns whether or not this `TransferSupport` represents a drop operation.
    `void` | `setDropAction(int dropAction)` Sets the drop action for the transfer - which must represent a drop - to the given action, instead of the default user drop action.
    `void` | `setShowDropLocation(boolean showDropLocation)` Sets whether or not the drop location should be visually indicated for the transfer - which must represent a drop.

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Constructor Detail

    - #### TransferSupport

          public TransferSupport(Component component,
                                 Transferable transferable)

      Create a `TransferSupport` with `isDrop()` `false` for the given component and `Transferable`.
      Parameters:
        `component` - the target component
        `transferable` - the transferable
      Throws:
        `NullPointerException` - if either parameter is `null`

  - ### Method Detail

    - #### isDrop

          public boolean isDrop()

      Returns whether or not this `TransferSupport` represents a drop operation.
      Returns:
        `true` if this is a drop operation, `false` otherwise.

    - #### getComponent

          public Component getComponent()

      Returns the target component of this transfer.
      Returns:
        the target component

    - #### getDropLocation

          public TransferHandler.DropLocation getDropLocation()

      Returns the current (non-`null`) drop location for the component, when this `TransferSupport` represents a drop.

      Note: For components with built-in drop support, this location will be a subclass of `DropLocation` of the same type returned by that component's `getDropLocation` method.

      This method is only for use with drag and drop transfers. Calling it when `isDrop()` is `false` results in an `IllegalStateException`.

      Returns:
        the drop location
      Throws:
        `IllegalStateException` - if this is not a drop
      See Also:
        `isDrop()`

    - #### setShowDropLocation

          public void setShowDropLocation(boolean showDropLocation)

      Sets whether or not the drop location should be visually indicated for the transfer - which must represent a drop. This is applicable to those components that automatically show the drop location when appropriate during a drag and drop operation). By default, the drop location is shown only when the `TransferHandler` has said it can accept the import represented by this `TransferSupport`. With this method you can force the drop location to always be shown, or always not be shown.

      This method is only for use with drag and drop transfers. Calling it when `isDrop()` is `false` results in an `IllegalStateException`.

      Parameters:
        `showDropLocation` - whether or not to indicate the drop location
      Throws:
        `IllegalStateException` - if this is not a drop
      See Also:
        `isDrop()`

    - #### setDropAction

          public void setDropAction(int dropAction)

      Sets the drop action for the transfer - which must represent a drop - to the given action, instead of the default user drop action. The action must be supported by the source's drop actions, and must be one of `COPY`, `MOVE` or `LINK`.

      This method is only for use with drag and drop transfers. Calling it when `isDrop()` is `false` results in an `IllegalStateException`.

      Parameters:
        `dropAction` - the drop action
      Throws:
        `IllegalStateException` - if this is not a drop
        `IllegalArgumentException` - if an invalid action is specified
      See Also:
        `getDropAction()`, `getUserDropAction()`, `getSourceDropActions()`, `isDrop()`

    - #### getDropAction

          public int getDropAction()

      Returns the action chosen for the drop, when this `TransferSupport` represents a drop.

      Unless explicitly chosen by way of `setDropAction`, this returns the user drop action provided by `getUserDropAction`.

      You may wish to query this in `TransferHandler`'s `importData` method to customize processing based on the action.

      This method is only for use with drag and drop transfers. Calling it when `isDrop()` is `false` results in an `IllegalStateException`.

      Returns:
        the action chosen for the drop
      Throws:
        `IllegalStateException` - if this is not a drop
      See Also:
        `setDropAction(int)`, `getUserDropAction()`, `isDrop()`

    - #### getUserDropAction

          public int getUserDropAction()

      Returns the user drop action for the drop, when this `TransferSupport` represents a drop.

      The user drop action is chosen for a drop as described in the documentation for `DropTargetDragEvent` and `DropTargetDropEvent`. A different action may be chosen as the drop action by way of the `setDropAction` method.

      You may wish to query this in `TransferHandler`'s `canImport` method when determining the suitability of a drop or when deciding on a drop action to explicitly choose.

      This method is only for use with drag and drop transfers. Calling it when `isDrop()` is `false` results in an `IllegalStateException`.

      Returns:
        the user drop action
      Throws:
        `IllegalStateException` - if this is not a drop
      See Also:
        `setDropAction(int)`, `getDropAction()`, `isDrop()`

    - #### getSourceDropActions

          public int getSourceDropActions()

      Returns the drag source's supported drop actions, when this `TransferSupport` represents a drop.

      The source actions represent the set of actions supported by the source of this transfer, and are represented as some bitwise-OR combination of `COPY`, `MOVE` and `LINK`. You may wish to query this in `TransferHandler`'s `canImport` method when determining the suitability of a drop or when deciding on a drop action to explicitly choose. To determine if a particular action is supported by the source, bitwise-AND the action with the source drop actions, and then compare the result against the original action. For example:

           boolean copySupported = (COPY & getSourceDropActions()) == COPY;

      This method is only for use with drag and drop transfers. Calling it when `isDrop()` is `false` results in an `IllegalStateException`.

      Returns:
        the drag source's supported drop actions
      Throws:
        `IllegalStateException` - if this is not a drop
      See Also:
        `isDrop()`

    - #### getDataFlavors

          public DataFlavor[] getDataFlavors()

      Returns the data flavors for this transfer.
      Returns:
        the data flavors for this transfer

    - #### isDataFlavorSupported

          public boolean isDataFlavorSupported(DataFlavor df)

      Returns whether or not the given data flavor is supported.
      Parameters:
        `df` - the `DataFlavor` to test
      Returns:
        whether or not the given flavor is supported.

    - #### getTransferable

          public Transferable getTransferable()

      Returns the `Transferable` associated with this transfer.

      Note: Unless it is necessary to fetch the `Transferable` directly, use one of the other methods on this class to inquire about the transfer. This may perform better than fetching the `Transferable` and asking it directly.

      Returns:
        the `Transferable` associated with this transfer

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