JFrame为什么不显示整个图像？

Question

Recently I have been experimenting with java graphics and decided to make a program that can print a Collage of images. The constructor for this program takes in an array of Images and the width that each image will be displayed at.

import java.awt.*;
import java.awt.image.BufferedImage; 
import java.awt.event.*;
import java.awt.image.*;
import java.io.*;
import javax.imageio.*;
import javax.swing.*;
public class CollageTest extends JComponent
{
    private  Image [][] board; //Holds images within it.
    private int pixel;//width of image.


    public CollageTest(Image x[][], int pixel)
    {
        board = x;
        this.pixel = pixel;
    }
    public int getPixel()
    {
        return pixel;
    }
    public void paint(Graphics g)
    {
        for (int i = 0; i < board.length; i++)
        {
            for (int j = 0; j < board[0].length; j++)
            {
                g.drawImage(board[i][j], (i * pixel) , (j * pixel), pixel, pixel, null);
            }
        }
    }




    public static void main(String args[])
    {
        BufferedImage[][] images = new BufferedImage[20][20];
        BufferedImage img = null;
        try {
            img = ImageIO.read(new File("gorge3.jpg"));
        } catch (IOException e) {
        }

        for (int i = 0; i < images.length; i++)
        {
            for (int j = 0; j < images[0].length; j++)
            {
                images[i][j] = img;
            }
        }
        CollageTest test = new CollageTest(images, 20);
        JFrame frame = new JFrame("MyCollage");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add(test);
        frame.setSize(test.getPixel() * images.length,test.getPixel() * images[0].length);
        frame.setVisible(true);
        test.repaint();

    }
}

To test the I initialized a CollageTest using an 20 x 20 array filled entirely with this Image.

When I ran the program originally I used The following to set the size of the JFrame's window:

frame.setSize(test.getPixel() * images.length,test.getPixel() * images[0].length);

Unfortunately the JFrame did display part of the image. The JFrame window did not go low enough down to display all of the window. To double double check that my math wasn't off, I tested using the following line in replacement:

frame.setSize(400, 400);//Math 20 images * 20 pixels = 400 pixels

The same problem occured. It was not until I used the following line that the entire image was displayed:

frame.setSize(400, 437);

So my question is, why is my JFrame misbehaving and is their a better way to fix it?

Answer 1

The problem lies in here:

frame.setSize(test.getPixel() * images.length,test.getPixel() * images[0].length);

You are manually setting the frame size according to the image size. However the frame size takes the title-bar and possibly borders into considerations. If the title-bar takes up 37 pixels, it leaves you 37 pixels lesser for the image.

What I would do is:

Add the image to a JPanel. You may set the size of the panel according to the image. pack() your JFrame after adding the panel containing your image so that it will determine the preferred size of the JFrame by itself.