Question

java的swing中,我想在JComboBox下拉框中添加文本内容,该如何去实现?

Answer 1

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

/*
* CustomComboBoxDemo.java 你要有下列文件
* images/Bird.gif
* images/Cat.gif
* images/Dog.gif
* images/Rabbit.gif
* images/Pig.gif
*/
public class CustomComboBoxDemo extends JPanel {
ImageIcon[] images;
String[] petStrings = {"Bird", "Cat", "Dog", "Rabbit", "Pig"};

/*
* Despite its use of EmptyBorder, this panel makes a fine content
* pane because the empty border just increases the panel's size
* and is "painted" on top of the panel's normal background. In
* other words, the JPanel fills its entire background if it's
* opaque (which it is by default); adding a border doesn't change
* that.
*/
public CustomComboBoxDemo() {
super(new BorderLayout());

//Load the pet images and create an array of indexes.
images = new ImageIcon[petStrings.length];
Integer[] intArray = new Integer[petStrings.length];
for (int i = 0; i < petStrings.length; i++) {
intArray[i] = new Integer(i);
images[i] = createImageIcon("images/" + petStrings[i] + ".gif");
if (images[i] != null) {
images[i].setDescription(petStrings[i]);
}
}

//Create the combo box.
JComboBox petList = new JComboBox(intArray);
ComboBoxRenderer renderer= new ComboBoxRenderer();
renderer.setPreferredSize(new Dimension(200, 130));
petList.setRenderer(renderer);
petList.setMaximumRowCount(3);

//Lay out the demo.
add(petList, BorderLayout.PAGE_START);
setBorder(BorderFactory.createEmptyBorder(20,20,20,20));
}

/** Returns an ImageIcon, or null if the path was invalid. */
protected static ImageIcon createImageIcon(String path) {
java.net.URL imgURL = CustomComboBoxDemo.class.getResource(path);
if (imgURL != null) {
return new ImageIcon(imgURL);
} else {
System.err.println("Couldn't find file: " + path);
return null;
}
}

/**
* 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("CustomComboBoxDemo");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

//Create and set up the content pane.
JComponent newContentPane = new CustomComboBoxDemo();
newContentPane.setOpaque(true); //content panes must be opaque
frame.setContentPane(newContentPane);

//Display the window.
frame.pack();
frame.setVisible(true);
}

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();
}
});
}

class ComboBoxRenderer extends JLabel
implements ListCellRenderer {
private Font uhOhFont;

public ComboBoxRenderer() {
setOpaque(true);
setHorizontalAlignment(CENTER);
setVerticalAlignment(CENTER);
}

/*
* This method finds the image and text corresponding
* to the selected value and returns the label, set up
* to display the text and image.
*/
public Component getListCellRendererComponent(
JList list,
Object value,
int index,
boolean isSelected,
boolean cellHasFocus) {
//Get the selected index. (The index param isn't
//always valid, so just use the value.)
int selectedIndex = ((Integer)value).intValue();

if (isSelected) {
setBackground(list.getSelectionBackground());
setForeground(list.getSelectionForeground());
} else {
setBackground(list.getBackground());
setForeground(list.getForeground());
}

//Set the icon and text. If icon was null, say so.
ImageIcon icon = images[selectedIndex];
String pet = petStrings[selectedIndex];
setIcon(icon);
if (icon != null) {
setText(pet);
setFont(list.getFont());
} else {
setUhOhText(pet + " (no image available)",
list.getFont());
}

return this;
}

//Set the font and text when no image was found.
protected void setUhOhText(String uhOhText, Font normalFont) {
if (uhOhFont == null) { //lazily create this font
uhOhFont = normalFont.deriveFont(Font.ITALIC);
}
setFont(uhOhFont);
setText(uhOhText);
}
}
}

Answer 2

在构造方法中穿进去
addItem(Object anObject)
JComboBox(Object[] items)
创建包含指定数组中的元素的 JComboBox。
JComboBox(Vector<?> items)
创建包含指定 Vector 中的元素的 JComboBox。

追问

我想实现的是将字符串添加到JComboBox下拉列表中
comboBox.setModel(new String[]("add","select","delete"));
我这样做的不行类型无法转换

追答

new JComboBox(new String[]("add","select","delete"))

Answer 3

JComboBox 构造方法源码
public JComboBox(E[] items) {
super();
setModel(new DefaultComboBoxModel<E>(items));
init();
}
创建对象赋值 new JComboBox<类型>(items);
有对象赋值 .setModel(new DefaultComboBoxModel<类型>(items));