DataFlavor
class allows you to specify the content type of your data.
You need to specify a DataFlavor
when fetching the data from the importData
method.
Several flavor types are predefined for you:
imageFlavor
represents data in the java.awt.Image
format. This is
used when dragging image data.
stringFlavor
represents data in the most basic
form of text — java.lang.String
. This is the most
commonly used data flavor for most applications.
javaFileListFlavor
represents java.io.File
objects in a java.util.List
format. This is useful for applications
that drag files, such as the TopLevelTransferHandler
example,
discussed in the
Top-Level Drop lesson.
For most applications, this is all you need to know about data flavors.
However, if you require a flavor other than these predefined types, you can
create your own. If you create a custom component and want it to
participate in data transfer, you will need to create a custom data flavor.
The constructor for specifying a data flavor is
DataFlavor(Class, String)
.
For example, to create a data flavor for the java.util.ArrayList
class:
new DataFlavor(ArrayList.class, "ArrayList");
new DataFlavor(int[].class, "Integer Array");
Transferring the data using this mechanism uses Object
serialization, so the class you use to transfer the data must
implement the Serializable
interface, as must anything
that is serialized with it. If everything is not
serializable, you will see a NotSerializableException
during drop or copy to the clipboard.
Creating a data flavor using the DataFlavor(Class, String)
constructor allows you to transfer data between applications, including
native applications. If you want to create a data flavor that
transfers data only within an application, use
and the
javaJVMLocalObjectMimeType
constructor. For example, to specify a data flavor that transfers
color from a DataFlavor(String)
JColorChooser
only within your application,
you could use this code:
String colorType = DataFlavor.javaJVMLocalObjectMimeType + ";class=java.awt.Color"; DataFlavor colorFlavor = new DataFlavor(colorType);
To create a data flavor for an ArrayList
that would
work only within your application:
new DataFlavor(DataFlavor.javaJVMLocalObjectMimeType + ";class=java.util.ArrayList");
To create a data flavor for an integer array:
new DataFlavor(DataFlavor.javaJVMLocalObjectMimeType + ";class=\"" + int[].class.getName() + "\"");
A MIME type containing special characters, such as [ or ;, must have those characters enclosed in quotes.
A Transferable
can be implemented to support multiple
flavors. For example, you can use both local and serialization flavors
together, or you can use two forms of the same data, such as the
ArrayList
and integer array flavors, together, or you
can create a TransferHandler
that accepts different types
of data, such as color and text.
When you create an array of DataFlavors
to be returned
from the Transferable
's
getTransferDataFlavors
method, the flavors should be inserted in preferred order, with
the most preferred appearing at element 0 of the array.
Genereally the preferred order is from the richest, or most complex,
form of the data down to the simpleset — the form most likely
to be understood by other objects.