如何向预先存在的Java组件添加新功能？

public class FadingButton extends JButton {

    //Constructors go here

    private void fadeButton(int timeToFade) {
        //Fade code goes here
    }
}

您还可以使用另一个类来装饰JButton：

public class JButtonDecorator {
    private JButton btn;

    //Constructor here

    private void fadeButton(int timeToFade) {
        //Fade code goes here,hiding the held button
    }

    //getter and setter method for button
}

或者,如果您想要许多不同的方式来影响您的UI,您可以创建一个实用程序类,类似于上面的：

//You could use a factory pattern to make this a singleton instead of having static methods
public abstract class UIUtils {

    private UIUtils{} //Don't instantiate this class

    public static void fadeComponent(JComponent toFade) {
        //Fade code goes here
    }

    //Other static utility methods
}

编辑：利用这些模式.扩展类是不言自明的,是简单继承的一个例子,所以它只是JButton的问题btn = new FadingButton();例如.以下是其他人：

要使用装饰器,请将其实例化为与您现在使用的按钮相同的范围.例如：

JButton myButton = new JButton();
//Customize button and add to UI
JButtonDecorator jbDec = new JButtonDecorator(myButton);

jbDec.fadeButton(20000);

虽然按钮是装饰器的一个字段,但它在UI中会正常运行.装饰器只是用有用的方法包装类,例如fadeButton方法.

要使用实用程序类,有两种方法.一个是两个用静态方法创建一个抽象类(如上所述),有些人认为它是坏形式,但它对简单程序有好处：

UIUtils.fadeComponent(myButton); //It's just that simple!
//The UIUtils class itself is never instantiated.
//All the methods are static,so no instances are needed.

或者,如果您想要更高级的方法,请将实用程序类设为单例.这会将实用程序类更改为：

public class UIUtils {

    UIUtils singleton;

    private UIUtils{} //Don't instantiate this class publicly

    public static UIUtils getInstance() {
        if(singleton==null) //This is the first time the method is called
             singleton = new UIUtils();
        return singleton; //Return the one instance of UIUtils
    }

    public void fadeComponent(JComponent toFade) {
        //Fade code goes here
    }

    //Other utility methods
}

然后,您将在类级别声明UIUtils对象以在UI中使用：

UIUtils uiUtil = UIUtils.getInstance();

在代码的某处：

uiUtil.fadeComponent(myButton);

这种模式对内存更有效,并且更加面向对象,但我个人并不认为它非常适合实用程序类.