使用Java AWT向面板添加图像

Question

我之前发布过一个有关面板混乱的帖子，但是通过简单地更改布局（感谢Charlie Martin的帮助），我解决了这个问题。现在，我正在尝试向面板添加一张图片，以便将该面板添加到框架中。这是我正在处理的类的一部分。

当我运行程序并点击启动游戏（在启动弹出窗口上）时，会出现以下内容： 基本上，主窗口应该有一张图片和按钮，但我不确定如何实现。

- Tyler

Answer 1

我建议在JLabel上设置一个ImageIcon，并将该JLabel添加到面板中的所需位置。

- Tom

Answer 2

请不要使用JLabel。虽然这是最简单的方法，但这也是不好的实践，并且在您有不是实际大小的图像要显示时会引起问题。

第二个答案走上了正确的道路，但仍然存在同样的问题。

这是我过去编写的一个类，这就是你需要的：

它还允许您设置特定的大小（如果需要）；它将缩放图像以最佳适合面板，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;
    }
}

- Reverend Gonzo

---

好的，我不需要你所说的所有功能：“如果需要，它也可以让你设置特定的大小；它会自动缩放图像以最佳适应面板，并对齐图像。”... 我只是想在程序中的按钮下添加一张图片。-_- - Tyler