我想为 JTree 中的元素着色。但是，仅向标签添加背景颜色看起来有点奇怪。特别是如果选择了多个节点，生成的形状看起来参差不齐且令人分心。

有没有办法让背景延伸到树元素的整个宽度，从而使整行都变色？要么从左边界开始，要么从标签的开头开始，但肯定延伸到组件的右边界？

这是一个独立的小演示，基于 this question .

import java.awt.*;
import javax.swing.*;
import javax.swing.tree.*;
public class SO26724913 {
    public static void main(String[] args) {
        DefaultMutableTreeNode a = new DefaultMutableTreeNode("a");
        DefaultMutableTreeNode b = new DefaultMutableTreeNode("b");
        DefaultMutableTreeNode c = new DefaultMutableTreeNode("c");
        a.add(b);
        a.add(c);
        final JTree tree = new JTree(a);
        tree.setCellRenderer(new DefaultTreeCellRenderer() {
                @Override
                public Component getTreeCellRendererComponent
                    (JTree tree, Object value, boolean selected,
                     boolean expanded, boolean leaf, int row, boolean focus)
                {
                    JComponent c = (JComponent)
                        super.getTreeCellRendererComponent
                        (tree, value, selected, expanded, leaf, row, focus);
                    DefaultMutableTreeNode node = (DefaultMutableTreeNode)value;
                    String data = (String)node.getUserObject();
                    if ("b".equals(data)) {
                        c.setBackground(Color.RED);
                        c.setOpaque(true);
                    }
                    else {
                        c.setBackground(null);
                        c.setOpaque(false);
                    }
                    return c;
                }
            });
        JFrame frm = new JFrame();
        frm.getContentPane().add(tree);
        frm.setSize(200, 200);
        frm.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frm.setVisible(true);
    }
}

这是代码当前生成的内容。

我更喜欢这个
或者这个。

最佳答案

您可以覆盖 JTree 的 paintComponent(Graphics) 方法来直接绘制选择矩形:

import java.awt.*;
import java.awt.event.*;
import java.util.Arrays;
import javax.swing.*;
import javax.swing.tree.*;

public class ColorTreeTest {
  private static final Color SELC = Color.RED;
  public JComponent makeUI() {
    FocusListener fl = new FocusListener() {
      @Override public void focusGained(FocusEvent e) {
        e.getComponent().repaint();
      }
      @Override public void focusLost(FocusEvent e) {
        e.getComponent().repaint();
      }
    };
    DefaultTreeCellRenderer r = new 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, false);
        l.setBackground(selected ? Color.RED
                                 : tree.getBackground());
        l.setOpaque(true);
        return l;
      }
    };
    JPanel p = new JPanel(new GridLayout(1, 2));
    for (JTree t : Arrays.asList(new ColorTree1(), new ColorTree2())) {
      t.addFocusListener(fl);
      t.setCellRenderer(r);
      t.setOpaque(false);
      p.add(new JScrollPane(t));
    }
    return p;
  }
  static class ColorTree1 extends JTree {
    @Override public void paintComponent(Graphics g) {
      g.setColor(getBackground());
      g.fillRect(0, 0, getWidth(), getHeight());
      if (getSelectionCount() > 0) {
        g.setColor(SELC);
        for (int i : getSelectionRows()) {
          Rectangle r = getRowBounds(i);
          g.fillRect(r.x, r.y, getWidth() - r.x, r.height);
        }
      }
      super.paintComponent(g);
      if (getLeadSelectionPath() != null) {
        Rectangle r = getRowBounds(getRowForPath(getLeadSelectionPath()));
        g.setColor(hasFocus() ? SELC.darker() : SELC);
        g.drawRect(r.x, r.y, getWidth() - r.x - 1, r.height - 1);
      }
    }
  }
  static class ColorTree2 extends JTree {
    private static final Color SELC = Color.RED;
    @Override public void paintComponent(Graphics g) {
      g.setColor(getBackground());
      g.fillRect(0, 0, getWidth(), getHeight());
      if (getSelectionCount() > 0) {
        g.setColor(SELC);
        //@see http://ateraimemo.com/Swing/TreeRowSelection.html
        for (int i : getSelectionRows()) {
          Rectangle r = getRowBounds(i);
          g.fillRect(0, r.y, getWidth(), r.height);
        }
      }
      super.paintComponent(g);
      if (getLeadSelectionPath() != null) {
        Rectangle r = getRowBounds(getRowForPath(getLeadSelectionPath()));
        g.setColor(hasFocus() ? SELC.darker() : SELC);
        g.drawRect(0, r.y, getWidth() - 1, r.height - 1);
      }
    }
  }
  public static void main(String... args) {
    EventQueue.invokeLater(new Runnable() {
      @Override public void run() {
        createAndShowGUI();
      }
    });
  }
  public static void createAndShowGUI() {
    JFrame f = new JFrame();
    f.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
    f.getContentPane().add(new ColorTreeTest().makeUI());
    f.setSize(320, 240);
    f.setLocationRelativeTo(null);
    f.setVisible(true);
  }
}

关于java - JTree 中的颜色行，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/26724913/