Java Reference
In-Depth Information
Don't forget to try out the tooltip for the Open button.
How It Works
After dealing with saving the current sketch in the
actionPerformed()
member of the
FileAction
class, you call the
showDialog()
method that you defined in the
SketcherFrame
class to display a file
open dialog. The
showDialog()
method is all-purpose — you can put any kind of label on the button or
any title in the title bar, so you can use it to display all of the dialogs you need for file operations.
If a file was chosen in the dialog that was displayed by the
actionPerformed()
method, you pass the
Path
object that the
showDialog()
returns to the
openSketch()
member of the
SketcherFrame
object
to read a new sketch from the file. The
openSketch()
method creates an
ObjectInputStream
object
from the
Path
object that was passed to it, and reads a
SketcherModel
object from the stream by calling
the
readObject()
method. The object returned by the
readObject()
method has to be cast to the ap-
propriate type —
SketcherModel
in this case.
You pass this
SketcherModel
object to the
insertModel()
method for the application object. This re-
places the current sketch reference in the
sketch
member of the application object with a reference to the
new sketch, and then sets the view and the application window as observers. Calling
repaint()
for the
view object displays the new sketch. The
paint()
method for the view object obtains a reference to the
current model by calling the
getModel()
member of the application object, which returns the reference
to the new model.
Starting a New Sketch
The File
⇒
New menu item simply starts a new sketch. This is quite similar to the open operation, except
that you must create an empty sketch rather than read a new one from disk. The processes of checking for
the need to save the current sketch and inserting the new
SketcherModel
object into the application are the
same.
TRY IT OUT: Implementing the New Operation
