[英]Can someone tell me where is it picking images from?
package demo;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
/*`enter code here`
* ComboBoxDemo.java uses these additional files:`enter code here`
* images/Bird.gif
* images/Cat.gif
* images/Dog.gif
* images/Rabbit.gif
* images/Pig.gif
*/
public class Demo extends JPanel
implements ActionListener {
JLabel picture;
@SuppressWarnings({ "rawtypes", "unchecked" })
public Demo() {
super(new BorderLayout());
String[] petStrings = { "Bird", "Cat", "Dog", "Rabbit", "Pig" };
//Create the combo box, select the item at index 4.
//Indices start at 0, so 4 specifies the pig.
JComboBox petList = new JComboBox(petStrings);
petList.setSelectedIndex(4);
petList.addActionListener(this);
//Set up the picture.
picture = new JLabel();
picture.setFont(picture.getFont().deriveFont(Font.ITALIC));
picture.setHorizontalAlignment(JLabel.CENTER);
updateLabel(petStrings[petList.getSelectedIndex()]);
picture.setBorder(BorderFactory.createEmptyBorder(10,0,0,0));
//The preferred size is hard-coded to be the width of the
//widest image and the height of the tallest image + the border.
//A real program would compute this.
picture.setPreferredSize(new Dimension(177, 122+10));
//Lay out the demo.
add(petList, BorderLayout.PAGE_START);
add(picture, BorderLayout.PAGE_END);
setBorder(BorderFactory.createEmptyBorder(20,20,20,20));
}
/** Listens to the combo box. */
public void actionPerformed(ActionEvent e) {
JComboBox cb = (JComboBox)e.getSource();
String petName = (String)cb.getSelectedItem();
updateLabel(petName);
}
protected void updateLabel(String name) {
ImageIcon icon = createImageIcon("images/" + name + ".png");
picture.setIcon(icon);
picture.setToolTipText("A drawing of a " + name.toLowerCase());
if (icon != null) {
picture.setText(null);
} else {
picture.setText("Image not found");
}
}
/** Returns an ImageIcon, or null if the path was invalid. */
protected static ImageIcon createImageIcon(String path) {
java.net.URL imgURL = Demo.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("ComboBoxDemo");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JComponent newContentPane = new Demo();
newContentPane.setOpaque(true);
frame.setContentPane(newContentPane);
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();
}
});
}
}
這是我從oracle那里獲得的代碼,但是我不知道從何處拾取圖像,因為每次我創建帶有圖像的源文件夾時,它仍然不會拾取它。 或者,如果您能告訴我代碼的哪一部分正在拾取圖像? 我的工作需要使用相同的代碼。
在Demo.java
所在的文件夾中創建一個名為images
的文件夾。 並將您的圖像放置在那里。 根據您的代碼,圖像名稱為“ Bird.png”,“ Cat.png”,“ Dog.png”,“ Rabbit.png”,“ Pig.png”。
所以您的項目結構是這樣的:
demo
src
└───demo
│ Demo.java
└───images
Bird.png
Cat.png
Dog.png
Rabbit.png
Pig.png
ImageIcon icon = createImageIcon("images/" + name + ".png");
該行提供的圖像路徑為images/name.png
, name
值可以在{"Bird", "Cat", "Dog", "Rabbit", "Pig"}
picture.setIcon(icon);
上一行將icon
設置為JLabel
picture
。
在項目的根目錄中創建一個名為images
的文件夾,並將所有.png
圖像放入images
文件夾中。
請參閱: http : //www.thinkplexx.com/learn/howto/java/system/java-resource-loading-explained-absolute-and-relative-names-difference-between-classloader-and-class-resource-loading
我終於找到了問題所在,但我不明白為什么他們用Oracle編寫代碼的方式行不通。
您需要轉到項目所在的文件夾。 您將看到:bin images src
images文件夾中可能包含所有預期的圖像文件,但是程序無法以某種方式獲取它們。 將gif文件復制到保存bin,圖像和src的文件夾中。
現在,您將看到:bin images src Bird.gif Cat.gif等。
現在返回並更改Oracle的代碼:
// ImageIcon圖標= createImageIcon(“ images /” +名稱+“ .gif”); //這種方式行不通。
至
ImageIcon icon = createImageIcon(name + ".gif");
如果要調試程序在何處提取文件,可以使用以下步驟創建File
對象並請求其絕對路徑。
System.out.println(new File("images/Bird.png").getAbsolutePath()); // C:\... or /...
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