使用 Java AWT 将图像添加到面板

Adding an image to a panel using Java AWT

提问by Tyler

I posted earlier about having a really messed up panel but, I fixed that by simply changing the layout (thank you to Charlie Martin for helping me). Now, I'm trying to add an image to a panel, so I can add that panel to the frame. This is part of the class that I am messing around with.

我之前发布过关于面板真的一团糟，但是，我通过简单地更改布局来解决这个问题（感谢 Charlie Martin 帮助我）。现在，我正在尝试将图像添加到面板中，以便我可以将该面板添加到框架中。这是我正在处理的课程的一部分。

http://friendpaste.com/13zibFC4oVxCbm83500KVj(dead link)

http://friendpaste.com/13zibFC4oVxCbm83500KVj（死链接）

This is what comes up when I run the program and hit start game (on the startup popup)..

这就是我运行程序并点击开始游戏（在启动弹出窗口中）时出现的情况。

Essentially, there is supposed to be an image on the main window along with the buttons and I'm not exactly sure how I would go about implementing this.

本质上，主窗口上应该有一个图像和按钮，我不确定我将如何实现它。

回答by Tom

I'd probably just set an ImageIcon on a JLabel and add the JLabel where you want in the panel.

我可能只是在 JLabel 上设置一个 ImageIcon 并在面板中您想要的位置添加 JLabel。

回答by Reverend Gonzo

Please, please, please -don't- use the JLabel. While that -is- the easiest way, it's also bad practice and causes problems when you have images that aren't the actual size you want displayed.

请，请，请 - 不要 - 使用 JLabel。虽然这是最简单的方法，但它也是不好的做法，并且当您的图像不是您想要显示的实际大小时会导致问题。

The second answer is on the right path, but still has the same problem.

第二个答案在正确的道路上，但仍然存在同样的问题。

Here's a class I've written in the past which is what you need:

这是我过去写的一个类，它是您需要的：

It will also allow you to set the specific size if you want; it will scale the image to best fit the panel, and align the image as well.

如果需要，它还允许您设置特定大小；它将缩放图像以最适合面板，并对齐图像。

import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.Insets;
import java.awt.print.PageFormat;
import java.awt.print.Printable;
import java.awt.print.PrinterException;
import java.io.File;

import javax.swing.ImageIcon;
import javax.swing.JComponent;
import javax.swing.SwingConstants;

public class ImagePanel extends JComponent implements SwingConstants, Printable {

    private Image image;
    private int verticalAlignment = CENTER;
    private int horizontalAlignment = CENTER;

    public ImagePanel() {}

    public ImagePanel(Image image) {
        setImage(image);
    }

    public Image getImage() {
        return image;
    }

    public void setImage(Image image) {
        this.image = image;
        repaint();
    }

    public void setImage(String file) {
        setImage(new ImageIcon(file).getImage());
    }

    public void setImage(File file) {
        setImage(new ImageIcon(file.getAbsolutePath()).getImage());
    }

    public void setImage(byte[] imageData) {
        setImage(imageData==null ? null : new ImageIcon(imageData).getImage());
    }

    public int getVerticalAlignment() {
        return verticalAlignment;
    }

    /**
     * @beaninfo
     *        bound: true
     *         enum: TOP    SwingConstants.TOP
     *               CENTER SwingConstants.CENTER
     *               BOTTOM SwingConstants.BOTTOM
     *    attribute: visualUpdate true
     *  description: The alignment of the image along the Y axis.  
     */
    public void setVerticalAlignment(int verticalAlignment) {
        if( (verticalAlignment==TOP) || (verticalAlignment==CENTER) || (verticalAlignment==BOTTOM) )
            this.verticalAlignment = verticalAlignment;
        else
            throw new IllegalArgumentException("Invalid Vertical Alignment: " + verticalAlignment);
    }

    public int getHorizontalAlignment() {
        return horizontalAlignment;
    }

    /**
     * @beaninfo
     *        bound: true
     *         enum: LEFT    SwingConstants.LEFT
     *               CENTER SwingConstants.CENTER
     *               RIGHT SwingConstants.RIGHT
     *    attribute: visualUpdate true
     *  description: The alignment of the image along the X axis.  
     */
    public void setHorizontalAlignment(int horizontalAlignment) {
        if( (horizontalAlignment==LEFT) || (horizontalAlignment==CENTER) || (horizontalAlignment==RIGHT) )
            this.horizontalAlignment = horizontalAlignment;
        else
            throw new IllegalArgumentException("Invalid Horizontal Alignment: " + horizontalAlignment);
    }

    @Override
    public Dimension getPreferredSize() {
        if(image == null)
            return super.getPreferredSize();
        else
            return new Dimension(image.getWidth(this), image.getHeight(this));
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);

        if(image==null)
            return;

        Insets insets = getInsets();
        int x = insets.left;
        int y = insets.top;

        int w = getWidth() - insets.left - insets.right;
        int h = getHeight() - insets.top - insets.bottom;

        int src_w = image.getWidth(null);
        int src_h = image.getHeight(null);

        double scale_x = ((double)w)/src_w;
        double scale_y = ((double)h)/src_h;

        double scale = Math.min(scale_x, scale_y);

        int dst_w = (int)(scale * src_w);
        int dst_h = (int)(scale * src_h);

        int dx = x + (w-dst_w)/2;
        if(horizontalAlignment==LEFT)
            dx = x;
        else if(horizontalAlignment==RIGHT)
            dx = x + w - dst_w; 

        int dy = y + (h-dst_h)/2;
        if(verticalAlignment==TOP)
            dy = y;
        else if(verticalAlignment==BOTTOM)
            dy = y + h - dst_h; 

        g.drawImage(image, dx, dy, dx+dst_w, dy+dst_h, 0, 0, src_w, src_h, null);
    }

    public int print(Graphics graphics, PageFormat pageFormat, int pageIndex) throws PrinterException {

        if(pageIndex>0 || image==null)
            return NO_SUCH_PAGE;

        double w = pageFormat.getImageableWidth();
        double h = pageFormat.getImageableHeight();

        int src_w = image.getWidth(null);
        int src_h = image.getHeight(null);

        double scale_x = w/src_w;
        double scale_y = h/src_h;

        double scale = Math.min(scale_x, scale_y);

        int dst_w = (int)(scale * src_w);
        int dst_h = (int)(scale * src_h);

        int dx = (int)((w-dst_w)/2);

        int dy = (int)((h-dst_h)/2);

        graphics.drawImage(image, dx, dy, dx+dst_w, dy+dst_h, 0, 0, src_w, src_h, null);

        return PAGE_EXISTS;
    }
}