keylistener_带有Java代码的KeyListener示例程序

谁借莪１个温暖的怀抱￠ 2022-12-07 12:10 174阅读 0赞

keylistener

The following [Java code][] shows an example program that implements the `KeyListener` interface. When executed, the Java code will show a very simple [Swing Graphical User Interface][].

以下[Java代码][Java code]显示了实现`KeyListener`接口的示例程序。 执行时，Java代码将显示一个非常简单的[Swing图形用户界面][Swing Graphical User Interface] 。

## 背景 **(** Background **)** ##

The [GUI][] is made up of a [`JFrame`][JFrame] which contains two `JTextAreas`. The first, `feedbackText` `JTextArea`, is placed inside a `JScrollPane` and is used to display text generated by the `KeyListener` events. The `JScrollPane` allows the user to see all the lines of text generated by the `KeyListener` events.

[GUI][]由包含两个`JTextAreas`的[`JFrame`][JFrame]组成。 第一个， `feedbackText` `JTextArea` ，放置在`JScrollPane`内部，用于显示`KeyListener`事件生成的文本。 `JScrollPane`允许用户查看`KeyListener`事件生成的所有文本行。

The second is the `inputText JTextArea`. This `JTextArea` has the focus and will generate `KeyListener` events as the user types into it. By default, the `inputArea JTextArea` will have the focus when the `JFrame` appears.

第二个是`inputText JTextArea` 。 此`JTextArea`具有焦点，并将在用户键入它时生成`KeyListener`事件。 默认情况下，当`JFrame`出现时， `inputArea JTextArea`将具有焦点。

The `KeyListener` interface could have been implemented as a separate class, or extending the `JFrame`, but in this instance using an anonymous inner class makes the most sense.

`KeyListener`接口可以实现为单独的类，也可以扩展`JFrame` ，但是在这种情况下，使用匿名内部类最有意义。

The `keyPressed` method is called when a user presses down on a key and the `keyReleased` method is called when a key is released. The `keyTyped` method is called when a character key is typed into the `inputText JTextArea`.

当用户按下某个键时，将调用`keyPressed`方法，而当释放一个键时，将调用`keyReleased`方法。 将字符键键入到`inputText JTextArea`时，将调用`keyTyped`方法。

## Java代码清单 **(** Java Code Listing **)** ##

import java.awt.BorderLayout;
    import java.awt.EventQueue;
    import java.awt.event.KeyEvent;
    import java.awt.event.KeyListener;
    import javax.swing.JFrame;
    import javax.swing.JTextArea;
    import javax.swing.JScrollPane;
    //Here's a class for a simple GUI that uses a JFrame
    //to hold to JTextAreas - one will listen for the key events
    //and the other will sit inside a JScrollPane providing feedback
    //about the KeyListener events being triggered
    public class KeyListenerExample {
    JTextArea inputText;
    JTextArea feedbackText;
    //Note: Typically the main method will be in a
    //separate class. As this is a simple one class
    //example it's all in the one class.
    public static void main(String[] args) {
    //Use the event dispatch thread for Swing components
    EventQueue.invokeLater(new Runnable()
    {
    @Override
    public void run()
    {
    new KeyListenerExample();
    }
    });
    }
    public KeyListenerExample()
    {
    JFrame guiFrame = new JFrame();
    //make sure the program exits when the frame closes
    guiFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    guiFrame.setTitle("Creating a Table Example");
    guiFrame.setSize(700,200);
    //This will center the JFrame in the middle of the screen
    guiFrame.setLocationRelativeTo(null);
    //This JTextArea is used to display information about
    //the keylistener events. It's place in a JScrollPane
    //to allow the scrolling through all the events triggered
    feedbackText = new JTextArea();
    JScrollPane scrollText = new JScrollPane(feedbackText);
    //This JTextArea will trigger the KeyListener events as
    //long as it hold the focus
    inputText = new JTextArea();
    //The KeyListener interface is implemented as an anonymous
    //inner class using the addKeyListener method.
    inputText.addKeyListener(new KeyListener()
    {
    //When any key is pressed and released then the
    //keyPressed and keyReleased methods are called respectively.
    //The keyTyped method is called when a valid character is typed.
    //The getKeyChar returns the character for the key used. If the key
    //is a modifier key (e.g., SHIFT, CTRL) or action key (e.g., DELETE, ENTER)
    //then the character will be a undefined symbol.
    @Override
    public void keyPressed(KeyEvent e)
    {
    feedbackText.append("Key Pressed: " + e.getKeyChar() + "\n");
    }
    @Override
    public void keyReleased(KeyEvent e)
    {
    feedbackText.append("Key Released: " + e.getKeyChar() + "\n");
    }
    @Override
    public void keyTyped(KeyEvent e)
    {
    //The getKeyModifiers method is a handy
    //way to get a String representing the
    //modifier key.
    feedbackText.append("Key Typed: " + e.getKeyChar() + " " + KeyEvent.getKeyModifiersText(e.getModifiers()) + "\n");
    }
    });
    guiFrame.add(inputText, BorderLayout.NORTH);
    guiFrame.add(scrollText, BorderLayout.CENTER);
    guiFrame.setVisible(true);
    }
    }

> 翻译自: [https://www.thoughtco.com/a-keylistener-example-program-2033900][https_www.thoughtco.com_a-keylistener-example-program-2033900]

keylistener

[Java code]: https://www.thoughtco.com/what-is-java-2034117
[Swing Graphical User Interface]: https://www.thoughtco.com/coding-a-simple-graphical-user-interface-2034064
[GUI]: https://www.thoughtco.com/gui-2034108
[JFrame]: https://www.thoughtco.com/create-a-simple-window-using-jframe-2034069
[https_www.thoughtco.com_a-keylistener-example-program-2033900]: https://www.thoughtco.com/a-keylistener-example-program-2033900