Personalize your application’s icon

Let your user customize the frame

Q: I’ve created a frame that extends from the Frame class. I’d like to change the top-left window icon to a user-defined icon. Is it possible?

A: This question comes up often. Luckily, there is a simple way to set a frame’s icon. If you look at the java.awt.Frame API, you’ll notice a method:

public void setIconImage(Image image);

To set the frame’s icon, you simply pass the setIconImage() method an image. (By the way, Swing’s JFrame works the same way, since it directly extends java.awt.Frame.)

You have a few options for obtaining your icon’s image, but it’s easiest to obtain it from the java.awt.Toolkit instance:

Toolkit.getDefaultToolkit().getImage("icon_name");

The Toolkit‘s getImage() method returns an image.

Calling the setIconImage on a standard java.awt.Frame instance works as I outlined above. It should work in your derived class as well. For a user-defined icon you’ll need to pass in an icon name at runtime. Three quick ways to do this are:

You could simply pass in the full path name of an icon on the command line as an argument. Of course, long startup strings will only annoy your user.
You can specify the full path name of an icon as a parameter:
```
-Dicon=icon_name.gif
```
When you specify a parameter on the command line you can easily retrieve the value by calling:
```
System.getProperty("icon")
```
Properties work through string/value pairs. The getProperty() method will return the string value for the key specified on the command line. Again, this is not the best approach, since it will annoy your users.
You can create a properties file. The properties file is similar to the second solution outlined above. However, instead of specifying the name/value pairs on the command line, specify them inside a file:
```
your_program.cfg
param1=value1
param2=value2
icon=icon_name.gif
...
paramN=valueN
```
To use the configuration file, create a java.util.Property instance, open the file with a java.io.FileInputStream, and load it into the Property by calling the Property‘s load() method. To obtain the icon name, call the Property‘s getProperty() method and pass it the string icon.