Drawing an Image to a JPanel within a JFrame

问题:

I am designing a program that contains two JPanels within a JFrame, one is for holding an image, the other for holding GUI components(Searchfields etc). I am wondering how do I draw the Image to the first JPanel within the JFrame?

Here is a sample code from my constructor :

public UITester() {
    this.setTitle("Airplane");
    Container container = getContentPane();
    container.setLayout(new FlowLayout());
    searchText = new JLabel("Enter Search Text Here");
    container.add(searchText);
    imagepanel = new JPanel(new FlowLayout());
    imagepanel.paintComponents(null);
   //other constructor code

}

public void paintComponent(Graphics g){
    super.paintComponents(g);
    g.drawImage(img[0], -50, 100, null);
}

I was trying to override the paintComponent method of JPanel to paint the image, but this causes a problem in my constructor when I try to write :

imagepanel.paintComponents(null);

As it will only allow me to pass the method null, and not Graphics g, anybody know of a fix to this method or another method i can use to draw the image in the JPanel? Help is appreciated! :)

All the best and thanks in advance! Matt

回答1:

I'd like to suggest a more simple way,

  image = ImageIO.read(new File(path));
  JLabel picLabel = new JLabel(new ImageIcon(image));

Yayy! Now your image is a swing component ! add it to a frame or panel or anything like you usually do! Probably need a repainting too , like

  jpanel.add(picLabel);
  jpanel.repaint(); 

回答2:

You can use the JLabel.setIcon() to place an image on the JPanel as shown here.

On the other hand, if you want to have a panel with a background, you can take a look at this tutorial.

回答3:

There is no need to manually invoke paintComponent() from a constructor. The problem is that you passing null for a Graphics object. Instead, override paintComponent() and you use the Graphics object passed in to the method you will be using for painting. Check this tutorial. Here is an example of JPanel with image:

class MyImagePanel extends JPanel{ 
    BufferedImage image;
    public void paintComponent(Graphics g){
        super.paintComponent(g);
        if(image != null){
            g.drawImage(image, 0, 0, this);
        }
    }
}