带有自定义项的Java Swing Jtree或Jlist

Question

有人可以解释一下，我怎样才能在Java Swing Desktop App中使用自定义项创建可扩展列表？我在Swing Desktop中有点新东西（通常我在Android上工作），我没有看到一些好的组件可以帮助我创建像图像上的图像和文本这样的列表。我想使用JTree，但我不确定我是否可以自定义它以获得我需要的结果。

Answer 1

以下是使用自定义TreeCellRenderer，Tree.closedIcon和Tree.openIcon的可能实施方式：

import java.awt.*;
import java.awt.geom.*;
import javax.swing.*;
import javax.swing.plaf.*;
import javax.swing.plaf.basic.*;
import javax.swing.tree.*;

public class CustomItemTreeTest {
  public JComponent makeUI() {
    IconUIResource emptyIcon = new IconUIResource(new Icon() {
      @Override public void paintIcon(Component c, Graphics g, int x, int y) {}
      @Override public int getIconWidth() {
        return 0;
      }
      @Override public int getIconHeight() {
        return 0;
      }
    });
    UIManager.put("Tree.expandedIcon",  emptyIcon);
    UIManager.put("Tree.collapsedIcon", emptyIcon);
    //UIManager.put("Tree.closedIcon",    emptyIcon);
    //UIManager.put("Tree.openIcon",      emptyIcon);
    UIManager.put("Tree.paintLines",    Boolean.FALSE);

    UIDefaults d = new UIDefaults();
    d.put("Tree:TreeCell[Enabled+Selected].backgroundPainter", new Painter<JComponent>() {
      @Override public void paint(Graphics2D g, JComponent c, int w, int h) {
        g.setPaint(Color.GREEN.darker());
        g.fillRect(0, 0, w, h);
      }
    });

    JTree tree = new JTree(makeModel());
    tree.setCellRenderer(new TestTreeCellRenderer());
    //tree.setRowHeight(0);
    tree.setRootVisible(false);
    tree.setShowsRootHandles(false);
    tree.setBackground(Color.WHITE);
    tree.putClientProperty("Nimbus.Overrides", d);
    tree.putClientProperty("Nimbus.Overrides.InheritDefaults", false);

    return new JScrollPane(tree);
  }

  private static TreeModel makeModel() {
    Dimension d64 = new Dimension(64, 64);
    Dimension d32 = new Dimension(32, 32);
    Dimension d24 = new Dimension(24, 24);
    DefaultMutableTreeNode root = new DefaultMutableTreeNode("Root");
    DefaultMutableTreeNode set1 = new DefaultMutableTreeNode(
        new TestNode("SubCategory 1", Color.ORANGE, d64, false));
    set1.add(new DefaultMutableTreeNode(
        new TestNode("SubSubCategory 1", Color.ORANGE, d32, true)));
    set1.add(new DefaultMutableTreeNode(
        new TestNode("SubSubCategory 2", Color.CYAN.darker(), d32, true)));
    set1.add(new DefaultMutableTreeNode(
        new TestNode("SubSubCategory 3", Color.GREEN, d32, true)));
    DefaultMutableTreeNode set2 = new DefaultMutableTreeNode(
        new TestNode("SubCategory 2", Color.GREEN.darker().darker(), d64, false));
    DefaultMutableTreeNode set3 = new DefaultMutableTreeNode(
        new TestNode("SubSubCategory 5", Color.GREEN, d32, false));
    set3.add(new DefaultMutableTreeNode(
        new TestNode("SubSubSubCategory 1", Color.BLUE, d24, true)));
    set3.add(new DefaultMutableTreeNode(
        new TestNode("SubSubSubCategory 2", Color.GREEN, d24, true)));
    set3.add(new DefaultMutableTreeNode(
        new TestNode("SubSubSubCategory 3", Color.ORANGE.darker(), d24, true)));
    set2.add(new DefaultMutableTreeNode(
        new TestNode("SubSubCategory 4", Color.ORANGE.darker().darker(), d32, true)));
    set2.add(set3);
    set2.add(new DefaultMutableTreeNode(
        new TestNode("SubSubCategory 6", Color.ORANGE, d32, true)));
    root.add(set1);
    root.add(set2);
    return new DefaultTreeModel(root);
  }

  public static void main(String... args) {
    EventQueue.invokeLater(() -> {
      try {
        for (UIManager.LookAndFeelInfo laf: UIManager.getInstalledLookAndFeels()) {
          if ("Nimbus".equals(laf.getName())) {
            UIManager.setLookAndFeel(laf.getClassName());
          }
        }
      } catch (Exception ex) {
        ex.printStackTrace();
      }
      JFrame f = new JFrame();
      f.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
      f.getContentPane().add(new CustomItemTreeTest().makeUI());
      f.setSize(320, 512);
      f.setLocationRelativeTo(null);
      f.setVisible(true);
    });
  }
}

class TestTreeCellRenderer extends DefaultTreeCellRenderer {
  @Override public Component getTreeCellRendererComponent(
      JTree tree, Object value, boolean selected, boolean expanded,
      boolean leaf, int row, boolean hasFocus) {
    JLabel l = (JLabel) super.getTreeCellRendererComponent(
        tree, value, selected, expanded, leaf, row, hasFocus);
    if (value instanceof DefaultMutableTreeNode) {
      DefaultMutableTreeNode node = (DefaultMutableTreeNode) value;
      Object uo = node.getUserObject();
      if (uo instanceof TestNode) {
        TestNode i = (TestNode) uo;
        l.setForeground(Color.BLACK);
        l.setIcon(new TestNode(i.title, i.color, i.dim, leaf, expanded));

        int indent = 0;
        TreeNode parent = node.getParent();
        while (parent instanceof DefaultMutableTreeNode) {
          DefaultMutableTreeNode pn = (DefaultMutableTreeNode) parent;
          if (pn.getUserObject() instanceof TestNode) {
            TestNode pi = (TestNode) pn.getUserObject();
            indent += pi.dim.width / 2;
          }
          parent = pn.getParent();
        }
        l.setBorder(BorderFactory.createEmptyBorder(2, indent, 2, 5));
      }
    }
    return l;
  }
}

class TestNode implements Icon {
  public final String title;
  public final Color color;
  public final Dimension dim;
  private final boolean expanded;
  private final boolean leaf;
  private static int GAP = 4;
  //public TestNode(String title, ImageIcon img, Dimension dim) {
  public TestNode(String title, Color color, Dimension dim, boolean leaf) {
    this(title, color, dim, leaf, false);
  }
  public TestNode(String title, Color color, Dimension dim,
                  boolean leaf, boolean expanded) {
    this.title = title;
    this.color = color;
    this.dim = dim;
    this.expanded = expanded;
    this.leaf = leaf;
  }
  @Override public void paintIcon(Component c, Graphics g, int x, int y) {
    g.setColor(color);
    g.fillRect(x + GAP, y + GAP, dim.width - GAP - GAP, dim.height - GAP - GAP);
    if (dim.width < 64) {
      Graphics2D g2 = (Graphics2D) g.create();
      g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                          RenderingHints.VALUE_ANTIALIAS_ON);
      int w6 = dim.width / 12;
      int w3 = dim.width / 6;
      g2.setColor(Color.WHITE);
      g2.setStroke(new BasicStroke(w6));
      Point pt = new Point(x + dim.width / 2, y + dim.height / 2);
      Path2D path = new Path2D.Double();
      path.moveTo(pt.x - w6, pt.y - w3);
      path.lineTo(pt.x + w6, pt.y);
      path.lineTo(pt.x - w6, pt.y + w3);
      int numquadrants;
      if (leaf) {
        numquadrants = 0;
      } else if (expanded) {
        numquadrants = 3;
      } else {
        numquadrants = 1;
      }
      AffineTransform at = AffineTransform.getQuadrantRotateInstance(
          numquadrants, pt.x, pt.y);
      g2.draw(at.createTransformedShape(path));
      g2.dispose();
    }
  }
  @Override public int getIconWidth() {
    return dim.width;
  }
  @Override public int getIconHeight() {
    return dim.height;
  }
  @Override public String toString() {
    return title;
  }
}