在java中的背景图片 [英] Background image in java

问题描述

我试图把图像作为我的Java接口的背景下，我试着写一个类，这是否和使用它，但有没有做一个简单的方法。

i'm trying to put an image as a background of my interface in java , i tried to write a class that does that and using it , but is there a simpler way to do that .

这里的<一个href=\"http://www.java-tips.org/java-se-tips/javax.swing/wrap-a-swing-jcomponent-in-a-background-image.html\"相对=nofollow> code 我使用：

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import javax.swing.BorderFactory;
import javax.swing.Icon;
import javax.swing.ImageIcon;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;

public class BackgroundImagePanelExample {

    // Set up contraints so that the user supplied component and the
    // background image label overlap and resize identically
    private static final GridBagConstraints gbc;

    static {
        gbc = new GridBagConstraints();
        gbc.gridx = 0;
        gbc.gridy = 0;
        gbc.weightx = 1.0;
        gbc.weighty = 1.0;
        gbc.fill = GridBagConstraints.BOTH;
        gbc.anchor = GridBagConstraints.NORTHWEST;
    }

    /**
     * Wraps a Swing JComponent in a background image. Simply invokes the overloded
     * variant with Top/Leading alignment for background image.
     *
     * @param component - to wrap in the a background image
     * @param backgroundIcon - the background image (Icon)
     * @return the wrapping JPanel
     */
    public static JPanel wrapInBackgroundImage(JComponent component,
        Icon backgroundIcon) {
        return wrapInBackgroundImage(
            component,
            backgroundIcon,
            JLabel.TOP,
            JLabel.LEADING);
    }

    /**
     * Wraps a Swing JComponent in a background image. The vertical and horizontal
     * alignment of background image can be specified using the alignment
     * contants from JLabel.
     *
     * @param component - to wrap in the a background image
     * @param backgroundIcon - the background image (Icon)
     * @param verticalAlignment - vertical alignment. See contants in JLabel.
     * @param horizontalAlignment - horizontal alignment. See contants in JLabel.
     * @return the wrapping JPanel
     */
    public static JPanel wrapInBackgroundImage(JComponent component,
        Icon backgroundIcon,
        int verticalAlignment,
        int horizontalAlignment) {

        // make the passed in swing component transparent
        component.setOpaque(false);

        // create wrapper JPanel
        JPanel backgroundPanel = new JPanel(new GridBagLayout());

        // add the passed in swing component first to ensure that it is in front
        backgroundPanel.add(component, gbc);

        // create a label to paint the background image
        JLabel backgroundImage = new JLabel(backgroundIcon);

        // set minimum and preferred sizes so that the size of the image
        // does not affect the layout size
        backgroundImage.setPreferredSize(new Dimension(1, 1));
        backgroundImage.setMinimumSize(new Dimension(1, 1));

        // align the image as specified.
        backgroundImage.setVerticalAlignment(verticalAlignment);
        backgroundImage.setHorizontalAlignment(horizontalAlignment);

        // add the background label
        backgroundPanel.add(backgroundImage, gbc);

        // return the wrapper
        return backgroundPanel;
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame("Background Image Panel Example");

        // Create some GUI
        JPanel foregroundPanel = new JPanel(new BorderLayout(10, 10));
        foregroundPanel.setBorder(
            BorderFactory.createEmptyBorder(10, 10, 10, 10));
        foregroundPanel.setOpaque(false);

        foregroundPanel.add(new JLabel("Comment:"), BorderLayout.NORTH);
        foregroundPanel.add(new JScrollPane(new JTextArea(3, 10)),
            BorderLayout.CENTER);
        foregroundPanel.add(
            new JLabel(
            "Please enter your comments in text box above."
            + " HTML syntax is allowed."), BorderLayout.SOUTH);

        frame.setContentPane(wrapInBackgroundImage(foregroundPanel,
            new ImageIcon(
            BackgroundImagePanelExample.class.getResource("backgd.jpg"))));

        frame.pack();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}

感谢

推荐答案

我猜你得到显示java.lang.NullPointerException ，因为 backgd.jpg 无法通过的 的getResource（） 。你也许可以把图像文件的源文件一起，重建项目。另外，也可以从文件系统加载它​​作为一项临时措施，而你理清头绪。

I'm guessing you're getting java.lang.NullPointerException because backgd.jpg can't be found by getResource(). You might be able to put the image file alongside the source file and rebuild the project. Alternatively, you can load it from the file system as a temporary measure while you sort things out.

frame.setContentPane(wrapInBackgroundImage(
    foregroundPanel, new ImageIcon("image.jpg")));

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