通过顶部面板显示背景图像

Question

当我在面板中添加面板和对象时，我希望将图像设置为背景并通过放在它上面的面板显示。我读到你可以通过设置 panel.setOpaque(false) 选项来做这个赌注，但这似乎不起作用。

这是我的编译器目录及其设置方式（使用 Intellij）...

这是背景图片...

这是代码...

背景面板class > http://www.camick.com/java/source/BackgroundPanel.java

/**
 * Created by James Page on 4/16/2017.
 */
package Main;

import org.apache.commons.lang3.ArrayUtils;

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.imageio.ImageIO;
import javax.swing.*;
import javax.swing.border.Border;
import javax.swing.border.TitledBorder;

public class TestGui extends JFrame {
    private final String[] guiCharSelDefault = {"---  Select Character ---"};
    private final String[] characters = {"charOne", "charTwo", "charThree", "charFour"};
    private final String[] GuiCharSel = (String[]) ArrayUtils.addAll(guiCharSelDefault, characters);
    private final String[] weapon = {"Weapon"};
    private final String[][] allWeapons = {
            {
                    "weakWeaponOne", "strongWeaponOne", "shortWeaponOne", "longWeaponOne"
            },
            {
                    "weakWeaponTwo", "strongWeaponTwo", "shortWeaponTwo", "longWeaponTwo"
            },
            {
                    "weakWeaponThree", "strongWeaponThree", "shortWeaponThree", "longWeaponThree"
            },
            {
                    "weakWeaponFour", "strongWeaponFour", "shortWeaponFour", "longWeaponFour"
            }
    };
    private JComboBox charCombo = new JComboBox(GuiCharSel);
    private JComboBox weaponsCombo = new JComboBox(weapon);
    private BackgroundPanel backgroundFrame = createBackgroundFrame("../images/Background.png");
    private JPanel topFrame = createTopFrame();
    private JPanel centerFrame = createCenterFrame();

    //**************************************************************************************

    private static GridBagConstraints setGbc(int gridx, int gridy, int gridWidth, int gridHeight, int ipadx, int ipady, String anchorLocation, double weightx, double weighty, Insets insets){
        GridBagConstraints gbc = new GridBagConstraints();

        if (anchorLocation.toUpperCase().equals("NORTHWEST")){
            gbc.anchor = GridBagConstraints.NORTHWEST;
        } else if (anchorLocation.toUpperCase().equals("NORTH")){
            gbc.anchor = GridBagConstraints.NORTH;
        } else if (anchorLocation.toUpperCase().equals("NORTHEAST")){
            gbc.anchor = GridBagConstraints.NORTHEAST;
        } else if (anchorLocation.toUpperCase().equals("WEST")){
            gbc.anchor = GridBagConstraints.WEST;
        } else if (anchorLocation.toUpperCase().equals("EAST")){
            gbc.anchor = GridBagConstraints.EAST;
        } else if (anchorLocation.toUpperCase().equals("SOUTHWEST")){
            gbc.anchor = GridBagConstraints.SOUTHWEST;
        } else if (anchorLocation.toUpperCase().equals("SOUTH")){
            gbc.anchor = GridBagConstraints.SOUTH;
        } else if (anchorLocation.toUpperCase().equals("SOUTHEAST")){
            gbc.anchor = GridBagConstraints.SOUTHEAST;
        } else {
            gbc.anchor = GridBagConstraints.CENTER;
        }

        gbc.gridx = gridx; // column
        gbc.gridy = gridy; // row
        gbc.gridwidth = gridWidth; // number of columns
        gbc.gridheight = gridHeight; // number of rows
        gbc.ipadx = ipadx; // width of object
        gbc.ipady = ipady; // height of object
        gbc.weightx = weightx; // shifts rows to side of set anchor
        gbc.weighty = weighty; // shifts columns to side of set anchor
        gbc.insets = insets; // placement inside cell
        gbc.fill = GridBagConstraints.HORIZONTAL;
        gbc.fill = GridBagConstraints.VERTICAL;

        return gbc;
    }

    private Insets setInsets(int top, int left, int bottom, int right){
        Insets insets = new Insets(top,left,bottom,right);
        return insets;
    }

    //**************************************************************************************

    private BackgroundPanel createBackgroundFrame(String imgLocName){
        Image backgroundImg = null;
        try {
            backgroundImg = ImageIO.read(getClass().getResource(imgLocName));
            System.out.println("File: " + imgLocName.toString());
        } catch (Exception e) {
            System.out.println("Cannot read file: " + e);
        }
        BackgroundPanel bgPanel = new BackgroundPanel(backgroundImg, BackgroundPanel.SCALED, 0.0f, 0.0f);
        return bgPanel;
    }

    private JPanel createTopFrame(){
        JPanel pnl = new JPanel();
        Border raisedBevel = BorderFactory.createRaisedBevelBorder();
        Color lineColor = new Color(224,224,224);
        Border lineBorder = BorderFactory.createMatteBorder(5, 5, 5, 5, lineColor);
        Border loweredBevel = BorderFactory.createLoweredBevelBorder();
        Border compoundSetup = BorderFactory.createCompoundBorder(raisedBevel, lineBorder);
        Border compoundFinal = BorderFactory.createCompoundBorder(compoundSetup, loweredBevel);
        TitledBorder topFrameTitle = BorderFactory.createTitledBorder(compoundFinal, "Character");
        topFrameTitle.setTitleJustification(TitledBorder.CENTER);

        JLabel lineSplitter = new JLabel();
        Border lineSplitterBoarder = BorderFactory.createMatteBorder(0, 0, 0, 5, new Color(224,224,224));
        lineSplitter.setBorder(lineSplitterBoarder);

        pnl.setBorder(topFrameTitle);
        pnl.setLayout(new GridBagLayout());
        pnl.setPreferredSize(new Dimension(200, 60));

        charCombo.addActionListener(
                new ActionListener() {
                    public void actionPerformed(ActionEvent e) {
                        String charName = ((JComboBox)(e.getSource())).getSelectedItem().toString();
                        if (charName.equals("charOne")){
                            weaponsCombo.removeAllItems();
                            weaponsCombo.setModel(new DefaultComboBoxModel(allWeapons[1]));
                        }
                    }
                }
        );
        pnl.add(charCombo, setGbc(0,0, 1,1, 0,0, "WEST", 0, 0, setInsets(0, 0, 0, 0)));
        pnl.add(lineSplitter, setGbc(1,0, 1,1, 0,0, "WEST", 0, 0, setInsets(0, 10, 0, 0)));
        pnl.add(weaponsCombo, setGbc(2,0, 1,1, 0,0, "WEST", 1, 1, setInsets(0, 10, 0, 0)));

        pnl.setOpaque(false);
        return pnl;
    }

    private JPanel createCenterFrame() {
        JPanel pnl = new JPanel();
        Border raisedBevel = BorderFactory.createRaisedBevelBorder();
        Color lineColor = new Color(224, 224, 224);
        Border lineBorder = BorderFactory.createMatteBorder(5, 5, 5, 5, lineColor);
        Border loweredBevel = BorderFactory.createLoweredBevelBorder();
        Border compoundSetup = BorderFactory.createCompoundBorder(raisedBevel, lineBorder);
        Border compoundFinal = BorderFactory.createCompoundBorder(compoundSetup, loweredBevel);
        TitledBorder topFrameTitle = BorderFactory.createTitledBorder(compoundFinal, "Stuff");
        topFrameTitle.setTitleJustification(TitledBorder.CENTER);

        pnl.setBorder(topFrameTitle);
        pnl.setLayout(new GridBagLayout());

        pnl.setOpaque(false);
        return pnl;
    }

    TestGui(){
        add(backgroundFrame);
        add(topFrame, BorderLayout.NORTH);
        add(centerFrame, BorderLayout.CENTER);

        setSize(800,600);
        setVisible(true);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }

    //**************************************************************************************

    public static void main(String[] args) {
        new TestGui();
    }
}

我知道图像背景被添加到 gui 中，因为如果我在构造函数中注释掉行 //add(topFrame, BorderLayout.NORTH); 和 //add(centerFrame, BorderLayout.CENTER);，图像就会显示在 gui 上。任何人都知道如何通过这两个面板显示背景图像？

Answer 1

您正在用 centerFrame

替换 backgroundFrame

add(backgroundFrame);
add(topFrame, BorderLayout.NORTH);
add(centerFrame, BorderLayout.CENTER);

这是 BorderLayout 的功能，它只能在 5 个可用位置中的每个位置支持一个组件

相反，您要做的是将其他面板添加到 backgroundFrame 或将 backgroundFrame 设置为框架的 contentPane，例如

setContentPane(backgroundFrame);
add(topFrame, BorderLayout.NORTH);
add(centerFrame, BorderLayout.CENTER);

另外，作为一般性建议，避免使用 setPreferredSize，有太多东西会导致出错

Sorry to bother you again, it looks like it is not showing through the JScrollPane. Should I open this up as a new question?

JScrollPane是一个比较复杂的组件，由两个组件组成，用于提供滚动功能

您需要使 JScrollPane 和它 JViewport 透明（以及您包装在其中的视图）

因此，这是您的 createCenterFrame 方法的修改版本，它创建一个 JTextArea，包装成一个 JScrollPane 并将其添加到 pnl

private JPanel createCenterFrame() {
    JPanel pnl = new JPanel();
    Border raisedBevel = BorderFactory.createRaisedBevelBorder();
    Color lineColor = new Color(224, 224, 224);
    Border lineBorder = BorderFactory.createMatteBorder(5, 5, 5, 5, lineColor);
    Border loweredBevel = BorderFactory.createLoweredBevelBorder();
    Border compoundSetup = BorderFactory.createCompoundBorder(raisedBevel, lineBorder);
    Border compoundFinal = BorderFactory.createCompoundBorder(compoundSetup, loweredBevel);
    TitledBorder topFrameTitle = BorderFactory.createTitledBorder(compoundFinal, "Stuff");
    topFrameTitle.setTitleJustification(TitledBorder.CENTER);

    pnl.setBorder(topFrameTitle);
    pnl.setLayout(new BorderLayout());

    JScrollPane scrollPane = new JScrollPane();
    scrollPane.setOpaque(false);
    scrollPane.getViewport().setOpaque(false);

    JTextArea ta = new JTextArea();
    ta.setOpaque(false);
    ta.setText("This is an example of a transparent text area inside a transparent scroll pane, but you could just as easily wrap a transparent panel into it and get the same result");
    ta.setWrapStyleWord(true);
    ta.setLineWrap(true);

    scrollPane.setViewportView(ta);

    pnl.add(scrollPane);

    pnl.setOpaque(false);
    return pnl;
}

通过顶部面板显示背景图像

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