Question

将图像保存到数据库时，我遇到了一个大问题。

我有JLabel名为personImage，当用户想要插入图片时，他必须点击personImage，然后会出现JFileChooser，用户可以选择一个图像。所选图像将加载到personImage。

当用户选择并保存图像时，它可以正常工作，但是当用户没有选择图像并且要保存详细信息时，它会给出NullPointerException。我认为这是因为没有路径可以将图像转换为文件对象。如何知道JLabel中是否有图像？我想检查是否有图像。

try {
    String fname = txt_Fname.getText();
    String lname = txt_Lname.getText();
    String mobile = txt_mobile.getText();
    String home = txt_home.getText();
    String work = txt_work.getText();
    String fax = txt_fax.getText();
    byte[] image_detail;

    PersonDAO perDAO = new PersonDAO(); //create person object
    if (status == 1) // used status  for check whether Jlabed is clicked
    {
        File image = new File(path);   
        FileInputStream fis = new FileInputStream(image); 
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        byte[] buf = new byte[1024];

        for (int readNum; (readNum = fis.read(buf)) != -1; )
        {
            baos.write(buf, 0,readNum);
        }
        image_detail =  baos.toByteArray();

        Person person1 = new Person(fname, lname, mobile, home, work, fax, image_detail); // call the person
        // constructer when there is an image. I did validate with status variable
            perDAO.InsertPerson(person1); // call the personDAO to insert the Person to database
        }
        else
        {
            Person person2 = new Person(lname, lname, mobile, home, work, fax); // if there is not an image call this constructer .
            perDAO.InsertPerson(person2); // then call to personDAO object to insert the person to  databasee
        }
    }
    catch (Exception exc)
    {
        System.out.println(exc + "sssssss");
    }


    // >>> when click on the JLabel, the JFileChooser appears
    int i = jFileChooser2.showOpenDialog(this);
    try {
        f = jFileChooser2.getSelectedFile();
        path = f.getAbsolutePath();
        ImageIcon image = new ImageIcon(path);
        status =  1;
        personImage.setIcon(image);
    }
    catch (Exception exc)
    {
        System.out.println(exc);
    }

Answer 1

如果您有JLabel label，请执行此操作以检查其是否有图标：

if (label.getIcon() == null) {
  // this means there is no icon
}

检查Jlabel是否有Icon

1 个答案: