java - JTable 上的 JToolTip - 未显示

Question

我正在尝试在 JTable 上实现 JToolTip，但是我遇到了一些问题。我在以下链接中找到了如何执行此操作的 Oracle 示例:

http://docs.oracle.com/javase/tutorial/uiswing/examples/components/TableToolTipsDemoProject/src/components/TableToolTipsDemo.java

public class test extends JPanel {
    private boolean DEBUG = false;
    protected String[] columnToolTips = {null,
                                         null,
                                         "The person's favorite sport to participate in",
                                         "The number of years the person has played the sport",
                                         "If checked, the person eats no meat"};

    public test() {
        super(new GridLayout(1,0));

        JTable table = new JTable(new MyTableModel()) {

            //Implement table cell tool tips.
            public String getToolTipText(MouseEvent e) {
                String tip = null;
                java.awt.Point p = e.getPoint();
                int rowIndex = rowAtPoint(p);
                int colIndex = columnAtPoint(p);
                int realColumnIndex = convertColumnIndexToModel(colIndex);

                if (realColumnIndex == 2) { //Sport column
                    tip = "This person's favorite sport to "
                           + "participate in is: "
                           + getValueAt(rowIndex, colIndex);
                } else if (realColumnIndex == 4) { //Veggie column
                    TableModel model = getModel();
                    String firstName = (String)model.getValueAt(rowIndex,0);
                    String lastName = (String)model.getValueAt(rowIndex,1);
                    Boolean veggie = (Boolean)model.getValueAt(rowIndex,4);
                    if (Boolean.TRUE.equals(veggie)) {
                        tip = firstName + " " + lastName
                              + " is a vegetarian";
                    } else {
                        tip = firstName + " " + lastName
                              + " is not a vegetarian";
                    }
                } else { 
                    //You can omit this part if you know you don't 
                    //have any renderers that supply their own tool 
                    //tips.
                    tip = super.getToolTipText(e);
                }
                return tip;
            }

            //Implement table header tool tips. 
            protected JTableHeader createDefaultTableHeader() {
                return new JTableHeader(columnModel) {
                    public String getToolTipText(MouseEvent e) {
                        String tip = null;
                        java.awt.Point p = e.getPoint();
                        int index = columnModel.getColumnIndexAtX(p.x);
                        int realIndex = columnModel.getColumn(index).getModelIndex();
                        return columnToolTips[realIndex];
                    }
                };
            }
        };

        table.setPreferredScrollableViewportSize(new Dimension(500, 70));
        table.setFillsViewportHeight(true);

        //Create the scroll pane and add the table to it.
        JScrollPane scrollPane = new JScrollPane(table);

        //Add the scroll pane to this panel.
        add(scrollPane);
    }

    class MyTableModel extends AbstractTableModel {
        private String[] columnNames = {"First Name",
                                        "Last Name",
                                        "Sport",
                                        "# of Years",
                                        "Vegetarian"};
        private Object[][] data = {
        {"Kathy", "Smith",
         "Snowboarding", new Integer(5), new Boolean(false)},
        {"John", "Doe",
         "Rowing", new Integer(3), new Boolean(true)},
        {"Sue", "Black",
         "Knitting", new Integer(2), new Boolean(false)},
        {"Jane", "White",
         "Speed reading", new Integer(20), new Boolean(true)},
        {"Joe", "Brown",
         "Pool", new Integer(10), new Boolean(false)}
        };

        public int getColumnCount() {
            return columnNames.length;
        }

        public int getRowCount() {
            return data.length;
        }

        public String getColumnName(int col) {
            return columnNames[col];
        }

        public Object getValueAt(int row, int col) {
            return data[row][col];
        }

        /*
         * JTable uses this method to determine the default renderer/
         * editor for each cell.  If we didn't implement this method,
         * then the last column would contain text ("true"/"false"),
         * rather than a check box.
         */
        public Class getColumnClass(int c) {
            return getValueAt(0, c).getClass();
        }

        /*
         * Don't need to implement this method unless your table's
         * editable.
         */
        public boolean isCellEditable(int row, int col) {
            //Note that the data/cell address is constant,
            //no matter where the cell appears onscreen.
            if (col < 2) {
                return false;
            } else {
                return true;
            }
        }

        /*
         * Don't need to implement this method unless your table's
         * data can change.
         */
        public void setValueAt(Object value, int row, int col) {
            if (DEBUG) {
                System.out.println("Setting value at " + row + "," + col
                                   + " to " + value
                                   + " (an instance of "
                                   + value.getClass() + ")");
            }

            data[row][col] = value;
            fireTableCellUpdated(row, col);

            if (DEBUG) {
                System.out.println("New value of data:");
                printDebugData();
            }
        }

        private void printDebugData() {
            int numRows = getRowCount();
            int numCols = getColumnCount();

            for (int i=0; i < numRows; i++) {
                System.out.print("    row " + i + ":");
                for (int j=0; j < numCols; j++) {
                    System.out.print("  " + data[i][j]);
                }
                System.out.println();
            }
            System.out.println("--------------------------");
        }
    }

    /**
     * Create the GUI and show it.  For thread safety,
     * this method should be invoked from the
     * event-dispatching thread.
     */
    private static void createAndShowGUI() {
        //Create and set up the window.
        JFrame frame = new JFrame("TableToolTipsDemo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        //Create and set up the content pane.
        JComponent newContentPane = new test();
        newContentPane.setOpaque(true); //content panes must be opaque
        frame.setContentPane(newContentPane);

        //Display the window.
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        //Schedule a job for the event-dispatching thread:
        //creating and showing this application's GUI.
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }
}

但是，当我编译并运行它时，没有显示任何工具提示？

任何关于为什么的帮助都会很棒，

谢谢。

Answer 1

根据您的代码片段getToolTipText()方法仅返回选择性列的工具提示，即(2,4)，对于标题，您有一个数组columnToolTips其中值仅指定 3,4,5 列。

所以，简而言之，您的代码运行得很好。请进行适当的更改，然后您就可以开始了。