JLayeredPane和GridBagConstraints [英] JLayeredPane and GridBagConstraints

问题描述

受此问题启发 带有LayoutManager的JLayeredPane 我正在尝试让JLayeredPane与GridBagLayout一起使用.

Inspired by this question JLayeredPane with a LayoutManager I'm trying to get the JLayeredPane to work with the GridBagLayout.

这是自定义的LayeredPane类:

Here's the custom 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，但适用于GridBagConstraints的使用，并去除了不必要的内容).

And here's a simple demo (similar to the standard-JLayeredPane demo but adapted for the usage of GridBagConstraints and stripped of the unnecessary stuff).

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();
            }
        });
    }

}

我的问题是我要添加6个(六个！)标签，但仅显示5个(五个！).第零只消失在某个地方.是什么原因呢?

My problem is that I'm adding 6 (six!) labels but only 5 (five!) are displayed. The 0-th one just vanishes somewhere. What's the reason for that?

编辑:追求这一目标的最初动机是将一个(部分透明的)组件放置在另一个组件的顶部，如此屏幕截图所示 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才能将其准确地放置在图表的顶部中间.

The initial motivation behind the pursuit is to place one (partially transparent) component on top of another like in this screenshot The label displaying 17:00:09 has transparent background and is placed on top of the chart-component. GridBagLayout is needed to place it exactly at the top middle of the chart.

推荐答案

• 正如@camickr所说，JLayeredPane无关紧要.
• 看看 GridBagLayout创建板| Oracle社区.可能有帮助.
  • As @camickr has already said, JLayeredPane is irrelevant.
  • Take a look at GridBagLayout to create a board | Oracle Community. May be it helps.

    达里尔·伯克(Darryl.Burke)说:
    除非至少有一个组件仅占据该列(或行)，否则GridBagLayout中的列(或行)定义不明确.您所有的行都有跨越2列的组件.

    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();
    }
  }
  

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