Question

所以我不希望textfeild打开一个文本文件，读取它，并将其内容复制到其中。我不希望这样。

我想知道的是如何使用此文本字段打开任何类型的文件。我已经尝试过这段代码，但它不起作用：

import java.awt.event.*;
import java.awt.*;
import java.io.File;
import java.io.IOException;

import javax.swing.*;
@SuppressWarnings("serial")
public class Console extends JFrame implements KeyListener{

TextArea c = new TextArea("", 30,30, TextArea.SCROLLBARS_VERTICAL_ONLY);
JTextField command = new JTextField(2);

public Console(String title) {
    super(title);

    c.setEditable(false);
    c.setBackground(Color.BLACK);
    c.setForeground(Color.GREEN);
    c.setFont(new Font("Courier", 12, 16));
    c.setText("Booted up the console" + "\n" + "Enter a command...");

    command.setBackground(Color.BLACK);
    command.setForeground(Color.GREEN);
    command.setFont(new Font("Courier", 12, 16));

    add(c, BorderLayout.PAGE_START);
    add(command, BorderLayout.PAGE_END);

    command.addKeyListener(this);
}

public void keyTyped(KeyEvent e) {

}
public void keyReleased(KeyEvent e) {

}
public void keyPressed(KeyEvent e) {
    int key = e.getKeyCode();
    if (key == KeyEvent.VK_ENTER) { 
        String COMMAND = command.getText();
        String otherCommand = command.getText();
        Desktop desktop = Desktop.getDesktop();
        File file = new File(otherCommand);
        String f = file.toString();
        if (COMMAND.equals("open")) {
            c.append("\n" + "Enter file to open:");
            if(otherCommand.equals(f)) {
                try {
                    desktop.open(file);
                } catch (IOException e1) {
                    c.append("Invalid file location");
                }
            }

        }
        if (COMMAND.equals("exit")) {
            c.append("\n" + "Exiting...");
            System.exit(0);
        }
    }
}

public void windowActivated(WindowEvent e){

}
public void windowDeactivated(WindowEvent e){

}
public void windowIconified(WindowEvent e){

}
public void windowDeiconified(WindowEvent e){

}
public void windowOpened(WindowEvent e){

}
public void windowClosing(WindowEvent e){
    System.exit(0);
}
public void windowClosed(WindowEvent e){
    System.exit(0);
}

}

我遇到的主要问题是这段代码：

public void keyPressed(KeyEvent e) {
        int key = e.getKeyCode();
        if (key == KeyEvent.VK_ENTER) { 
            String COMMAND = command.getText();
            String otherCommand = command.getText();
            Desktop desktop = Desktop.getDesktop();
            File file = new File(otherCommand);
            String f = file.toString();
            if (COMMAND.equals("open")) {
                c.append("\n" + "Enter file to open:");
                if(otherCommand.equals(f)) {
                    try {
                        desktop.open(file);
                    } catch (IOException e1) {
                        c.append("Invalid file location");
                    }
                }

            }
            if (COMMAND.equals("exit")) {
                c.append("\n" + "Exiting...");
                System.exit(0);
            }
        }
    }

我收到此错误：

Exception in thread "AWT-EventQueue-0" java.lang.IllegalArgumentException: The file: open doesn't exist.
at java.awt.Desktop.checkFileValidation(Unknown Source)
at java.awt.Desktop.open(Unknown Source)
at com.parth.Console.keyPressed(Console.java:52)
at java.awt.Component.processKeyEvent(Unknown Source)
at javax.swing.JComponent.processKeyEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.KeyboardFocusManager.redispatchEvent(Unknown Source)
at java.awt.DefaultKeyboardFocusManager.dispatchKeyEvent(Unknown Source)
at java.awt.DefaultKeyboardFocusManager.preDispatchKeyEvent(Unknown Source)
at java.awt.DefaultKeyboardFocusManager.typeAheadAssertions(Unknown Source)
at java.awt.DefaultKeyboardFocusManager.dispatchEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$500(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

Answer 1

您的代码存在一些问题：

command.addKeyListener(this);

对于大多数与Swing密钥相关的代码，您将希望避免使用KeyListener，因为它是一个低级侦听器，并且仅在组件具有焦点时才处于活动状态。更多的问题是在JTextField中使用它，因为这样做可以阻止JTextField的一些关键核心行为。最好使用DocumentListener，但实际上在你的情况下，使用ActionListener要好得多。

关于：

String COMMAND = command.getText();
String otherCommand = command.getText();
Desktop desktop = Desktop.getDesktop();
File file = new File(otherCommand);
String f = file.toString();
if (COMMAND.equals("open")) {
    c.append("\n" + "Enter file to open:");
    if (otherCommand.equals(f)) {
        try {
            desktop.open(file);
        } catch (IOException e1) {
            c.append("Invalid file location");
        }
    }
}

在这里，您需要在用户输入任何新文本之前从命令JTextField 获取文本。

关于：

public class Console extends JFrame implements KeyListener {

通过让您的类扩展JFrame，迫使您创建和显示JFrame，通常需要更多的灵活性，您在角落里画画。事实上，我冒昧地说，我创建的大部分Swing GUI代码和我见过的不扩展了JFrame，事实上你很少想做这个。更常见的是，您的GUI类将面向创建JPanels，然后可以将其放置到JFrames或JDialogs或JTabbedPanes中，或者在需要时通过CardLayouts交换。这将大大提高GUI编码的灵活性。

此外，您将不希望您的GUI类实现您的侦听器接口，因为这会给类一个太多不同的责任。要么使用匿名内部类，要么使用私有内部类，或者如果要为侦听器使用单独的独立类。

您要做的是再次使用ActionListener，并根据用户输入的内容更改其状态。如果用户输入“open”，则可能将openFile boolean设置为true，并且在侦听器内，如果为true，则在下次调用actionPerformed时，获取的String将用于打开文件。或者您可以使用枚举来保存ActionListener的状态。例如：

import java.awt.BorderLayout; import java.awt.Component; import java.awt.Desktop; import java.awt.Window; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.io.File; import java.io.IOException; import javax.swing.*; public class Console2 extends JPanel { private static final String INTRO_TEXT = "Booted up the console" + "\n" + "Enter a command...\n"; private static final String ENTER_FILE_PROMPT = "Enter file to open:\n"; private static final String OPEN = "open"; private static final String EXIT = "exit"; public static final String USER_PROMPT = "User > "; private JTextArea textArea = new JTextArea(INTRO_TEXT, 20, 40); private JTextField inputField = new JTextField(); public Console2() { // have text area wrap lines textArea.setLineWrap(true); textArea.setWrapStyleWord(true); // have it not get focus textArea.setFocusable(false); JScrollPane scrollPane = new JScrollPane(textArea); scrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS); // ***** this is it! Add an ActionListener to our JTextField. ***** inputField.addActionListener(new InputListener()); setLayout(new BorderLayout()); add(scrollPane, BorderLayout.CENTER); add(inputField, BorderLayout.PAGE_END); } // listener state enum InputState { GETTING_COMMAND, OPEN_FILE } private class InputListener implements ActionListener { private InputState state = InputState.GETTING_COMMAND; @Override public void actionPerformed(ActionEvent e) { // get input text and clear the field String inputText = inputField.getText().trim(); inputField.setText(""); textArea.append(USER_PROMPT + inputText + "\n"); if (state == InputState.GETTING_COMMAND) { if (OPEN.equalsIgnoreCase(inputText)) { state = InputState.OPEN_FILE; // change the listener's state textArea.append(ENTER_FILE_PROMPT); // prompt user } if (EXIT.equalsIgnoreCase(inputText)) { Window window = SwingUtilities .getWindowAncestor(Console2.this); window.dispose(); } } else if (state == InputState.OPEN_FILE) { state = InputState.GETTING_COMMAND; // reset Desktop desktop = Desktop.getDesktop(); File file = new File(inputText); if (!file.exists()) { Component parentComponent = Console2.this; Object message = "File " + file.toString() + " does not exist"; String title = "Error Attempting to Open File"; int messageType = JOptionPane.ERROR_MESSAGE; JOptionPane.showMessageDialog(parentComponent, message, title, messageType); } else { try { desktop.open(file); } catch (IOException e1) { Component parentComponent = Console2.this; Object message = e1.getMessage(); String title = "Error Attempting to Open File"; int messageType = JOptionPane.ERROR_MESSAGE; JOptionPane.showMessageDialog(parentComponent, message, title, messageType); e1.printStackTrace(); } } } } } private static void createAndShowGui() { Console2 mainPanel = new Console2(); JFrame frame = new JFrame("Console2"); frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE); frame.getContentPane().add(mainPanel); frame.pack(); frame.setLocationByPlatform(true); frame.setVisible(true); } public static void main(String[] args) { SwingUtilities.invokeLater(new Runnable() { public void run() { createAndShowGui(); } }); } }

另一种选择是当输入“打开”时，显示JFileChooser以允许用户选择现有文件。

Answer 2

堆栈跟踪中的消息，

at com.parth.Console.keyPressed(Console.java:52)

这对应于下面的行（假设你的实际代码中还有2行额外的（包声明后跟新行？），

desktop.open(file);

Javadoc表示当文件不存在时，使用IllegalArgumentException类open方法时，您将获得Desktop。

IllegalArgumentException - 如果指定的文件不存在

请在调用file.getName()方法之前打印open，并验证您尝试打开的文件是否确实存在

如何从文本域打开任何文件？

2 个答案: