Java IO.pdf - Nguyen Dang Binh

Java I/O
don't want to. File dialogs are modal. While the file dialog is shown, input to the parent frame
is blocked, as with the parent frame of any modal dialog. The title argument is the prompt
string for the file dialog, normally something like "Please choose the file to open:". The mode
argument is one of the two mnemonic constants FileDialog.LOAD or FileDialog.SAVE:
public static final int LOAD = 0;
public static final int SAVE = 1;
Use FileDialog.LOAD if you want the user to choose a file to open. Use FileDialog.SAVE if
you want the user to choose a file to save the data into. A typical use of this constructor might
look like this:
FileDialog fd = new FileDialog(new Frame("Dummy frame"),
"Please choose the file to open:", FileDialog.LOAD);
To specify that the file dialog should appear with a particular directory opened or a particular
file in that directory selected, you can invoke the setDirectory() and setFile() methods:
public synchronized void setDirectory(String directory)
public synchronized void setFile(String file)
For example:
fd.setDirectory("/etc");
fd.setFile("passwd");
You make the file dialog visible by invoking the file dialog's show() method, just like any
other window:
fd.show();
As soon as the file dialog becomes visible, the calling thread stops and waits for the user to
choose a file. The operating system takes over and handles user interaction until the user
chooses a file or presses the Cancel button. At this point, the file dialog disappears from the
screen, and normal program execution resumes.
Once the dialog has been dismissed, you can find out which file the user chose by using the
file dialog's getDirectory() and getFile() methods:
public String getFile()
public String getDirectory()
For example:
FileDialog fd = new FileDialog(new Frame(), "Please choose a file:",
FileDialog.LOAD);
fd.setVisible(true);
File f = new File(fd.getDirectory(), fd.getFile());
If the user cancels the file dialog without selecting a file, getFile() and getDirectory()
return null. You should be ready to handle this, or you'll bump into a
NullPointerException in short order.
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