我正在尝试使用自定义图像更改JComboBox的下拉箭头,但该代码似乎无法正常工作。我遵循了here的指示。我尝试同时使用Java 1.8.131和AdoptOpenJDK 11.0.5,但两者的结果相同。在下面,您可以找到我正在使用的完整代码:
Main.java
public static void main(String[] args) throws ClassNotFoundException, InstantiationException, IllegalAccessException, UnsupportedLookAndFeelException {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
JFrame f = new JFrame("Window");
JPanel panel = new JPanel();
panel.setBounds(0, 0, 400, 400);
panel.setBackground(Color.gray);
JComboBox<String> box = new JComboBox<>();//simple JComboBox with custom UI
box.setPreferredSize(new Dimension(150, 30));
box.setUI(MyBasicComboboxUI.createUI(box));
box.addItem("BasicComboBoxUI1");
box.addItem("BasicComboBoxUI2");
box.addItem("BasicComboBoxUI3");
panel.add(box);
JButton btn = new JButton("SimpleJButton");//simple JButton with an image on it (to prove that the image loads)
btn.setPreferredSize(new Dimension(120, 30));
MyImageProvider imageProvider = new MyImageProvider();
btn.setIcon(new ImageIcon(imageProvider.getImage()));
btn.setBorder(new EmptyBorder(0, 0, 0, 0));
panel.add(btn);
f.add(panel);
f.setSize(400, 400);
f.setLayout(null);
f.setVisible(true);
f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
}
MyBasicComboboxUI.java:
public class MyBasicComboboxUI extends BasicComboBoxUI {
public static ComboBoxUI createUI(JComponent c) {
return new MyBasicComboboxUI();
}
@Override
protected JButton createArrowButton() {
JButton arrowButton = super.createArrowButton();
MyImageProvider imgProvider = new MyImageProvider();
arrowButton.setSize(new Dimension(40, 40));
arrowButton.setToolTipText("My tooltip");
arrowButton.setIcon(new ImageIcon(imgProvider.getImage()));//set the same icon here
arrowButton.setBorder(new EmptyBorder(0, 0, 0, 0));
return arrowButton;
}
}
MyImageProvider.java
public class MyImageProvider {
public Image getImage() {
try {
Image img = ImageIO.read(getClass().getResource("/icons/arrow.gif"));
return img;
} catch (IOException e) {
System.out.println("The image was not loaded.");
}
return null;
}
}
运行程序时的输出:
在箭头上设置的工具提示正在起作用。如果使用自定义背景色,则相同。但如果我设置图像,则不会。我尝试使用:* .jpg,*。gif,*。png和其他分辨率:16x16、14x14、12x12、8x8等,但均未成功。在所有情况下,图像仅加载在SimpleJButton上,而不加载在组合框的下拉箭头按钮上。
Eclipse结构:
您的问题是线路
JButton arrowButton = super.createArrowButton();
您应该将其更改为
JButton arrowButton = new JButton();
背景:super.createArrowButton()
返回ArrowButton
类的实例,该类提供自定义箭头绘制,但不支持setIcon
方法。