JLayeredPane 和 GridBagConstraints

Question

受这个问题启发 JLayeredPane with a LayoutManager 我正在尝试让 JLayeredPane 与 GridBagLayout 一起工作。

这是自定义 LayeredPane-class:

class StackConstraints {
    public final int layer;
    public final Object layoutConstraints;

    public StackConstraints(int layer, Object layoutConstraints) {
        this.layer = layer;
        this.layoutConstraints = layoutConstraints;
    }
}

class LXLayeredPane extends JLayeredPane {

    private static final long serialVersionUID = 1946283565823567689L;

    @Override
    protected void addImpl(Component comp, Object constraints, int index) {
        int layer = 0;
        int pos = 0;
        Object constr = null;
        if (constraints instanceof StackConstraints) {
            layer = ((StackConstraints) constraints).layer;
            constr = ((StackConstraints) constraints).layoutConstraints;
        } else {
            layer = getLayer(comp);
            constr = constraints;
        }

        pos = insertIndexForLayer(layer, index);
        super.addImpl(comp, constr, pos);
        setLayer(comp, layer, pos);
        comp.validate();
        comp.repaint();
    }
}

这是一个简单的演示（类似于标准 JLayeredPane 演示，但针对 GridBagConstraints 的使用进行了调整并删除了不必要的内容）。

public class LayeredPaneDemo extends JPanel implements ActionListener {
    private final Color[] layerColors = { Color.yellow, Color.magenta, Color.cyan, Color.red, Color.green, Color.blue };

    private final JLayeredPane layeredPane;
    private final List<JLabel> labels;

    private JButton update;

    public LayeredPaneDemo() {
        setLayout(new BoxLayout(this, BoxLayout.PAGE_AXIS));

        labels = new ArrayList<>();

        layeredPane = new LXLayeredPane();
        layeredPane.setPreferredSize(new Dimension(400, 410));
        layeredPane.setBorder(BorderFactory.createTitledBorder("Click to change colors"));

        // Add several labels to the layered pane.
        layeredPane.setLayout(new GridBagLayout());
        for (int i = 0; i < layerColors.length; i++) {
            JLabel label = createColoredLabel("Test", layerColors[i]);
            labels.add(label);
            layeredPane.add(label, new StackConstraints(i, gbc(i)));
        }

        // Add control pane and layered pane to this JPanel.
        add(Box.createRigidArea(new Dimension(0, 10)));
        add(createControlPanel());
        add(Box.createRigidArea(new Dimension(0, 10)));
        add(layeredPane);
    }

    private GridBagConstraints gbc(int i) {
        return new GridBagConstraints(i, i, 2, 2, 0.0, 0.0, GridBagConstraints.CENTER, GridBagConstraints.BOTH,
                new Insets(0, 0, 0, 0), 0, 0);
    }

    // Create and set up a colored label.
    private JLabel createColoredLabel(String text, Color color) {
        JLabel label = new JLabel(text);
        label.setVerticalAlignment(JLabel.TOP);
        label.setHorizontalAlignment(JLabel.CENTER);
        label.setOpaque(true);
        label.setBackground(color);
        label.setForeground(Color.black);
        label.setBorder(BorderFactory.createLineBorder(Color.black));
        label.setPreferredSize(new Dimension(240, 240));
        return label;
    }

    // Create the control pane for the top of the frame.
    private JPanel createControlPanel() {
        update = new JButton("Update");
        update.addActionListener(this);
        update.setActionCommand("UPDATE");

        JPanel controls = new JPanel();
        controls.add(update);
        controls.setBorder(BorderFactory.createTitledBorder("Choose Duke's Layer and Position"));
        return controls;
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        Color prev = labels.get(labels.size() - 1).getBackground();

        for (int i = labels.size() - 1; i > 0; --i) {
            labels.get(i).setBackground(labels.get(i - 1).getBackground());
            labels.get(i).validate();
            labels.get(i).repaint();
        }
        labels.get(0).setBackground(prev);
        labels.get(0).validate();
        labels.get(0).repaint();
    }

    private static void createAndShowGUI() {
        JFrame frame = new JFrame("LayeredPaneDemo2");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JComponent newContentPane = new LayeredPaneDemo();
        newContentPane.setOpaque(true);
        frame.setContentPane(newContentPane);

        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                createAndShowGUI();
            }
        });
    }

}

我的问题是我添加了 6（六个！）个标签，但只显示了 5（五个！）个。第 0 个就消失在某个地方。这是什么原因？

编辑：追求背后的最初动机是将一个（部分透明的）组件放在另一个组件之上，就像这个截图显示 17:00:09 的标签具有透明背景，并放置在图表组件的顶部。需要 GridBagLayout 才能将其准确放置在图表的顶部中间。

Answer 1

is there a fundamental reason why I cannot mix layers and GridBagLayout?

这就是我的观点。我认为您不需要自定义 JLayeredPane。

分层窗格用于对面板进行分层。

然后每个单独的面板都可以有自己的布局管理器，无论是 GridBagLayout、FlowLayout 还是其他。

例如，尝试更新在 LayeredPaneDemo:

中创建标签的循环

JLabel label = null; 

for (int i = 0; i < layerStrings.length; i++) {
    //JLabel label = createColoredLabel(layerStrings[i], layerColors[i], origin);
    label = createColoredLabel(layerStrings[i], layerColors[i], origin);
    layeredPane.add(label, new Integer(i));
    origin.x += offset;
    origin.y += offset;
}

label.setLayout( new GridBagLayout() );
label.add(new JCheckBox("Check Me"), new GridBagConstraints() );

以上代码将使用默认约束向标签添加一个复选框，这意味着该复选框将在标签内居中。

我不知道您不能在分层窗格中的每个面板上使用不同布局管理器的任何原因。如果布局不是您所期望的，那么我猜您的 GridBagConstrainsts 不正确。

Answer 2

正如@camickr 已经说过的，JLayeredPane 是无关紧要的。
看看GridBagLayout to create a board | Oracle Community。可能有帮助。

Darryl.Burke said:
A column (or row) in a GridBagLayout is not well defined unless there is at least one component which occupies only that column (or row). All your rows have components spanning 2 columns.

import java.awt.*;
import java.awt.event.*;
import java.util.ArrayList;
import java.util.List;
import javax.swing.*;
import javax.swing.table.*;

public class LayeredPaneDemo2 extends JPanel implements ActionListener {
  private final Color[] layerColors = {
      Color.yellow, Color.magenta, Color.cyan,
      Color.red, Color.green, Color.blue };

  private final JLayeredPane layeredPane;
  private final List<JLabel> labels;

  private JButton update;

  public LayeredPaneDemo2() {
    setLayout(new BoxLayout(this, BoxLayout.PAGE_AXIS));

    labels = new ArrayList<>();
    // JLayeredPane is not much related, it is a problem of how to use GridBagLayout.
    layeredPane = new LXLayeredPane();
    layeredPane.setPreferredSize(new Dimension(400, 410));
    layeredPane.setBorder(BorderFactory.createTitledBorder(
        "Click to change colors"));

    // Add several labels to the layered pane.
    layeredPane.setLayout(new GridBagLayout());

    for (int i = 0; i < layerColors.length; i++) {
      JLabel label = createColoredLabel("Test" + i, layerColors[i]);
      labels.add(label);
      layeredPane.add(label, new StackConstraints(i, gbc(i)));
    }
//     //TEST1: Create reference grid
//     GridBagConstraints c = new GridBagConstraints(
//       0, 0, 1, 1, 0.0, 0.0, GridBagConstraints.CENTER,
//       GridBagConstraints.BOTH, new Insets(0, 0, 0, 0), 0, 0);
//     for (int i = 0; i < layerColors.length + 1; i++) {
//       c.gridx = i;
//       c.gridy = i;
//       layeredPane.add(Box.createRigidArea(new Dimension(20, 20)), c);
//     }
    //TEST2: Create reference grid >>>
    GridBagConstraints c = new GridBagConstraints(
        6, 6, 1, 1, 0.0, 0.0, GridBagConstraints.CENTER,
        GridBagConstraints.BOTH, new Insets(0, 0, 0, 0), 0, 0);
    for (int i = 0; i < layerColors.length; i++) {
      c.gridx = i;
      Component box = Box.createRigidArea(new Dimension(20, 20));
      ((JComponent) box).setBorder(BorderFactory.createLineBorder(Color.RED));
      layeredPane.add(box, c);
    }
    c.gridx = 6;
    for (int i = 0; i < layerColors.length; i++) {
      c.gridy = i;
      Component box = Box.createRigidArea(new Dimension(20, 20));
      ((JComponent) box).setBorder(BorderFactory.createLineBorder(Color.RED));
      layeredPane.add(box, c);
    }
    // <<<
    // Add control pane and layered pane to this JPanel.
    add(Box.createRigidArea(new Dimension(0, 10)));
    add(createControlPanel());
    add(Box.createRigidArea(new Dimension(0, 10)));
    add(layeredPane);
  }

  private GridBagConstraints gbc(int i) {
    return new GridBagConstraints(
        i, i, 2, 2, 0.0, 0.0, GridBagConstraints.CENTER,
        GridBagConstraints.BOTH, new Insets(0, 0, 0, 0), 0, 0);
  }

  // Create and set up a colored label.
  private JLabel createColoredLabel(String text, Color color) {
    JLabel label = new JLabel(text) {
      @Override protected void paintComponent(Graphics g) {
        g.setColor(new Color(100, 100, 100, 100));
        g.fillRect(0, 0, getWidth(), getHeight());
        super.paintComponent(g);
      }
    };
    label.setVerticalAlignment(JLabel.TOP);
    label.setHorizontalAlignment(JLabel.CENTER);
    label.setOpaque(true);
    label.setBackground(color);
    label.setForeground(Color.black);
    label.setBorder(BorderFactory.createLineBorder(Color.black));
    label.setPreferredSize(new Dimension(240, 240));
    return label;
  }

  // Create the control pane for the top of the frame.
  private JPanel createControlPanel() {
    update = new JButton("Update");
    update.addActionListener(this);
    update.setActionCommand("UPDATE");

    JPanel controls = new JPanel();
    controls.add(update);
    controls.setBorder(BorderFactory.createTitledBorder(
        "Choose Duke's Layer and Position"));
    return controls;
  }

  @Override
  public void actionPerformed(ActionEvent e) {
    Color prev = labels.get(labels.size() - 1).getBackground();

    for (int i = labels.size() - 1; i > 0; --i) {
      labels.get(i).setBackground(labels.get(i - 1).getBackground());
      labels.get(i).validate();
      labels.get(i).repaint();
    }
    labels.get(0).setBackground(prev);
    labels.get(0).validate();
    labels.get(0).repaint();
  }

  private static void createAndShowGUI() {
    JFrame frame = new JFrame("LayeredPaneDemo2");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    JComponent newContentPane = new LayeredPaneDemo2();
    newContentPane.setOpaque(true);
    frame.setContentPane(newContentPane);

    frame.pack();
    frame.setVisible(true);
  }

  public static void main(String[] args) {
    javax.swing.SwingUtilities.invokeLater(new Runnable() {
      @Override
      public void run() {
        createAndShowGUI();
      }
    });
  }

}

class StackConstraints {
  public final int layer;
  public final Object layoutConstraints;

  public StackConstraints(int layer, Object layoutConstraints) {
    this.layer = layer;
    this.layoutConstraints = layoutConstraints;
  }
}

class LXLayeredPane extends JLayeredPane {
  @Override
  protected void addImpl(Component comp, Object constraints, int index) {
    int layer = 0;
    int pos = 0;
    Object constr = null;
    if (constraints instanceof StackConstraints) {
      layer = ((StackConstraints) constraints).layer;
      constr = ((StackConstraints) constraints).layoutConstraints;
    } else {
      layer = getLayer(comp);
      constr = constraints;
    }

    pos = insertIndexForLayer(layer, index);
    super.addImpl(comp, constr, pos);
    setLayer(comp, layer, pos);
    comp.validate();
    comp.repaint();
  }
}

JLayeredPane 和 GridBagConstraints

JLayeredPane and GridBagConstraints

java

swing

layout-manager

jlayeredpane

gridbaglayout