我需要部分Java代码的帮助. [英] I need help with part of Java code.

问题描述

此代码没有任何错误.我想知道是否有人可以告诉我这是否是使用

I do not get any errors with this code. I was wondering if anyone could tell me if this is the correct way to use the

setFocusTraversalPolicy

的正确方法

class FocusHandler implements FocusListener

    {

        public void focusGained (FocusEvent e)

        {

            if(e.getSource() == lengthField || e.getSource() == widthField)

            {

                areaField.setText("");

            }

            else if (e.getSource() == areaField)

            {

                areaField.setFocusTraversalPolicy(null);

                calculateButton.grabFocus();



                // or maybe calculateButton.requestFocusInWindow();

            }

        }

        public void focusLost(FocusEvent e)

        {

            if(e.getSource() == widthField)

            {

                widthField.setFocusTraversalPolicy(null);

                calculateButton.grabFocus();



            }

        }

    }

推荐答案

这是FocusListener的一部分.它们通常被实现为接口，并称为处理程序.您可以匿名使用它们，或让某些Worker-class获取接口.

在此处阅读: http://docs.oracle.com/javase/tutorial/uiswing/events/focuslistener .html [^ ]

..有关各种侦听器的更多信息.

This is part of a FocusListener. They are often implemented as Interfaces and called Handler. You can use them anonymous or let some Worker-class get the interface.

Read here: http://docs.oracle.com/javase/tutorial/uiswing/events/focuslistener.html[^]

..much much more about Listeners of all kind.

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