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我正在製作一個包含1個TextArea，1個Label和1個TextField的Java Swing應用程序。Swing apllication在ActionEvent上拋出java.lang.NullPointerException
我的代碼如下：當按下回車鍵
package mainpack.newboston;
import java.awt.Color;
import java.awt.Container;
import java.awt.Insets;
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextArea;
import javax.swing.JTextField;
public class Panel extends JPanel implements ActionListener {
protected JTextArea textarea123;
protected JTextField textfield1;
JLabel label;
JFrame frame;
public Panel() {
setLayout(null);
JTextArea textarea123 = new JTextArea();
JTextField textfield1 = new JTextField(30);
JLabel label = new JLabel("Command: ");
add(textarea123);
add(textfield1);
add(label);
// textarea123.append("Hello");
textarea123.setEditable(false);
textarea123.setSize(600, 600);
textarea123.setBackground(Color.BLACK);
textarea123.setForeground(Color.WHITE);
textfield1.setBorder(null);
textfield1.setBackground(Color.BLACK);
textfield1.setForeground(Color.white);
textfield1.addActionListener(this);
textfield1.setActionCommand("commandexecuted");
// label.setForeground(Color.WHITE);
label.setBackground(Color.ORANGE);
//#######################################################
Insets insets = getInsets();
Dimension fieldsize = textfield1.getPreferredSize();
textfield1.setBounds(63 + insets.left, 555 + insets.top, 537, fieldsize.height);
textfield1.setFocusable(true);
textfield1.setEnabled(true);
Dimension labelsize = label.getPreferredSize();
label.setBounds(0 + insets.left, 555 + insets.top, labelsize.width, labelsize.height);
@SuppressWarnings("unused")
Dimension size = textarea123.getPreferredSize();
textarea123.setBounds(0 + insets.left, 0 + insets.top, 600, 555);
//##########################################################
}
/**
* Create the GUI and show it. For thread safety,
* this method should be invoked from the
* event-dispatching thread.
*/
private static void createAndShowGUI() {
//Create and set up the window.
JFrame frame = new JFrame("New Boston");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//Set up the content pane.
frame.add(new Panel());
//Size and display the window.
Insets insets = frame.getInsets();
frame.setResizable(false);
frame.setSize(600 + insets.left + insets.right, 600 + insets.top + insets.bottom);
frame.setVisible(true);
}
public void ConsoleLog(String message){
System.out.println(message);
}
public static void main(String[] args) {
//Schedule a job for the event-dispatching thread:
//creating and showing this application's GUI.
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
public void textappend(String message) {
textarea123.append(message);
}
public void actionPerformed(ActionEvent evt) {
if (evt.getActionCommand().equals("commandexecuted")) {
if (textfield1.getText().equals("Try")) {
ConsoleLog("Hello");
}
}
}
}
錯誤信息，而文本字段是重點：
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at mainpack.newboston.Panel.actionPerformed(Panel.java:127)
at javax.swing.JTextField.fireActionPerformed(Unknown Source)
at javax.swing.JTextField.postActionEvent(Unknown Source)
at javax.swing.JTextField$NotifyAction.actionPerformed(Unknown Source)
at javax.swing.SwingUtilities.notifyAction(Unknown Source)
at javax.swing.JComponent.processKeyBinding(Unknown Source)
at javax.swing.JComponent.processKeyBindings(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$400(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)
我想使它看起來像一個控制檯，並使用一些命令，但我會稍後做，因爲我不能使用ActionEvents ...
真的，那麼容易嗎？我試圖修復這個小時......很多謝謝:)） – BGdeveloper
爲您的文本區域和標籤做同樣的事情。 – Kapparino