Java 组合框上的动作侦听器以在 textField 中显示选择
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时间：2020-08-14 12:19:55 来源:igfitidea点击:
Action listener on comboBox to display selection in textField
提问by Kevin Schultz
I have a comboBox that contains selections. I am trying to apply an actionListener to display te selected string on a textField. I am not sure how to complete this and all I have read is confusing me even more.
我有一个包含选择的组合框。我正在尝试应用 actionListener 在 textField 上显示选定的字符串。我不知道如何完成这个，我读到的所有内容让我更加困惑。
Here is the code for the comboBox:
这是组合框的代码：
JComboBox comboBox = new JComboBox();
comboBox.setModel(new DefaultComboBoxModel(new String[] {"Select Something", "Selection 1", "Selection 2", "Selection 3", "Selection 4"}));
panelTop.add(comboBox);
comboBox.setPreferredSize(new Dimension(160, 20));
comboBox.addItem("Select Something");
textField Code:
文本字段代码：
textField = new JTextField();
panelTop.add(textField);
textField.setColumns(40);
What I have so far on the actionListener:
到目前为止我在 actionListener 上的内容：
public void actionPerformed(ActionEvent e) {
JComboBox comboBox = (JComboBox)e.getSource();
String newSelection = (String)comboBox.getSelectedItem();
currentPattern = newSelection;
}
Full Code:
完整代码：
package SwingAssign2;
import java.awt.Dimension;
import java.awt.EventQueue;
import javax.swing.BorderFactory;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextPane;
import java.awt.BorderLayout;
import javax.swing.JComboBox;
import javax.swing.JTextField;
import java.awt.FlowLayout;
import javax.swing.SwingConstants;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import javax.swing.DefaultComboBoxModel;
public class SwingAssign2 {
private JFrame frame;
private JTextField textField;
/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
SwingAssign2 window = new SwingAssign2();
window.frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the application.
*/
public SwingAssign2() {
initialize();
}
/**
* Initialize the contents of the frame.
*/
private void initialize() {
frame = new JFrame();
frame.setSize(600, 500);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel panelTop = new JPanel();
FlowLayout fl_panelTop = (FlowLayout) panelTop.getLayout();
fl_panelTop.setAlignment(FlowLayout.LEFT);
frame.getContentPane().add(panelTop, BorderLayout.NORTH);
//panel.setLayout(new FlowLayout(FlowLayout.LEFT, 5, 5));
final JComboBox comboBox = new JComboBox();
comboBox.setModel(new DefaultComboBoxModel(new String[] {"Select Something", "Selection 1", "Selection 2", "Selection 3", "Selection 4"}));
panelTop.add(comboBox);
comboBox.setPreferredSize(new Dimension(160, 20));
comboBox.addItem("Select Something");
textField = new JTextField();
panelTop.add(textField);
textField.setColumns(40);
JPanel panelBottom = new JPanel();
frame.getContentPane().add(panelBottom, BorderLayout.SOUTH);
panelBottom.setLayout(new BorderLayout(0, 0));
JLabel status = new JLabel("Status");
status.setHorizontalAlignment(SwingConstants.CENTER);
panelBottom.add(status, BorderLayout.SOUTH);
status.setBorder(BorderFactory.createLoweredBevelBorder());
JTextPane txtpnSomeContentOn_B = new JTextPane();
txtpnSomeContentOn_B.setText("Some content on the bottom panel\r\nMore content\r\nSome more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content");
JScrollPane jScrollPane3 = new JScrollPane(txtpnSomeContentOn_B);
jScrollPane3.setHorizontalScrollBarPolicy(
JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
jScrollPane3.setVerticalScrollBarPolicy(
JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
panelBottom.add(jScrollPane3, BorderLayout.NORTH);
jScrollPane3.setPreferredSize(new Dimension(200, 200));
//bText.setBorder(BorderFactory.createLoweredBevelBorder());
JPanel panelCenter = new JPanel();
frame.getContentPane().add(panelCenter, BorderLayout.CENTER);
panelCenter.setLayout(new GridLayout(0, 2, 0, 0));
JTextPane txtpnSomeContentOn_0 = new JTextPane();
txtpnSomeContentOn_0.setText("Some content on the left panel\r\nMore content\r\nSome more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content");
JScrollPane jScrollPane1 = new JScrollPane(txtpnSomeContentOn_0);
jScrollPane1.setHorizontalScrollBarPolicy(
JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
jScrollPane1.setVerticalScrollBarPolicy(
JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
panelCenter.add(jScrollPane1);
JTextPane txtpnSomeContentOn = new JTextPane();
txtpnSomeContentOn.setText("Some content on the right panel\r\nMore content\r\nSome more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content\r\nMore and more content");
JScrollPane jScrollPane2 = new JScrollPane(txtpnSomeContentOn);
jScrollPane2.setHorizontalScrollBarPolicy(
JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
jScrollPane2.setVerticalScrollBarPolicy(
JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
panelCenter.add(jScrollPane2);
comboBox.addItemListener(new ItemListener() {
@Override
public void itemStateChanged(ItemEvent e) {
if(e.getStateChange() == ItemEvent.SELECTED) {
textField.setText((String) comboBox.getSelectedItem());
}
}
});
}
}
采纳答案by David Yee
Consider adding an ItemListenerto the JComboBoxand checking that the ItemEventstate is ItemEvent.SELECTED. You can set the text field's text in the itemStateChangedmethod:
考虑添加ItemListener到JComboBox和检查的ItemEvent状态ItemEvent.SELECTED。您可以在itemStateChanged方法中设置文本字段的文本：
comboBox.addItemListener(new ItemListener() {
@Override
public void itemStateChanged(ItemEvent e) {
if(e.getStateChange() == ItemEvent.SELECTED) {
textField.setText((String) comboBox.getSelectedItem());
}
}
});
回答by MikeM
You're on the right track. I'm not sure what the context is for your existing actionListener, but one way you could do it is as follows:
你在正确的轨道上。我不确定您现有的 actionListener 的上下文是什么，但您可以这样做的一种方法如下：
comboBox.addItemListener(new ItemListener() {
@Override
public void itemStateChanged(ItemEvent arg0) { // picks up changes to combobox selection
if (arg0.getStateChange() == ItemEvent.SELECTED) {
String newSelection = comboBox.getSelectedItem(); // takes the selected item
textField.setText(newSelection); // publishes to the textfield
}
}
});
回答by Braj
I am trying to apply an actionListener to display te selected string on a textField
我正在尝试应用 actionListener 在 textField 上显示选定的字符串
Add ActionListeneron JComboBoxadd set the text in JTextField.
添加ActionListener在JComboBox附加设置文本JTextField。
Sample code:
示例代码：
final JTextField jTextField = new JTextField();
final JComboBox<String> comboBox = new JComboBox<String>();
comboBox.setModel(new DefaultComboBoxModel<String>(new String[] {
"Select Something", "Selection 1", "Selection 2",
"Selection 3", "Selection 4" }));
// set first one selected
comboBox.setSelectedIndex(0);
comboBox.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent ae) {
// check whether there is any selection
if(comboBox.getSelectedIndex()!=-1){
jTextField.setText(comboBox.getSelectedItem().toString());
}
}
});
It's worth reading How to Use Combo Boxes
值得一读如何使用组合框
Few Points:
几点：
- Always try to avoid RAW type. Make it Generic Type.
- Use
JFrame#pack()instead ofJFrame#setSize() Never use
setPreferredSize()instead use proper layout that is responsible for component size and position, if extremely needed then override JComponent#getPreferredSize().Read more Should I avoid the use of set(Preferred|Maximum|Minimum)Size methods in Java Swing?
- 总是尽量避免 RAW 类型。使其成为通用类型。
- 使用
JFrame#pack()代替JFrame#setSize() 永远不要使用
setPreferredSize()负责组件大小和位置的正确布局，如果非常需要，则覆盖 JComponent#getPreferredSize()。阅读更多我应该避免在 Java Swing 中使用 set(Preferred|Maximum|Minimum)Size 方法吗？
For example:
例如：
final JPanel panel = new JPanel(){
@Override
public Dimension getPreferredSize() {
return new Dimension(...,...);
}
};
回答by lakshman
add an ActionListenerin which override the actionPerformedmethod, to the combo box. see my working example below
在组合框中添加一个ActionListener覆盖该actionPerformed方法的方法。请参阅下面的我的工作示例
import java.awt.EventQueue;
import java.util.Vector;
import javax.swing.DefaultComboBoxModel;
import javax.swing.GroupLayout;
import javax.swing.GroupLayout.Alignment;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.border.EmptyBorder;
import javax.swing.JComboBox;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
public class JTextFieldTest extends JFrame {
private JPanel contentPane;
private JTextField textField;
/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
JTextFieldTest frame = new JTextFieldTest();
frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the frame.
*/
public JTextFieldTest() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setBounds(100, 100, 298, 220);
contentPane = new JPanel();
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
setContentPane(contentPane);
Vector<String> comboBoxItems=new Vector();
comboBoxItems.add("A");
comboBoxItems.add("B");
comboBoxItems.add("C");
final DefaultComboBoxModel model = new DefaultComboBoxModel(comboBoxItems);
final JComboBox comboBox = new JComboBox(model);
comboBox.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {//here your actionPerformed method
textField.setText((String) comboBox.getSelectedItem());
}
});
textField = new JTextField();
textField.setColumns(10);
GroupLayout gl_contentPane = new GroupLayout(contentPane);
gl_contentPane.setHorizontalGroup(
gl_contentPane.createParallelGroup(Alignment.LEADING)
.addGroup(gl_contentPane.createSequentialGroup()
.addGroup(gl_contentPane.createParallelGroup(Alignment.LEADING)
.addGroup(gl_contentPane.createSequentialGroup()
.addGap(110)
.addComponent(comboBox, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE))
.addGroup(gl_contentPane.createSequentialGroup()
.addGap(83)
.addComponent(textField, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE)))
.addContainerGap(103, Short.MAX_VALUE))
);
gl_contentPane.setVerticalGroup(
gl_contentPane.createParallelGroup(Alignment.LEADING)
.addGroup(gl_contentPane.createSequentialGroup()
.addGap(37)
.addComponent(comboBox, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE)
.addGap(18)
.addComponent(textField, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE)
.addContainerGap(76, Short.MAX_VALUE))
);
contentPane.setLayout(gl_contentPane);
}
}
