Question

我正在尝试构建jTable，其中我有一个很重的（不是很重）绘制jTable的每个单元格的任务。但我不是经常画画（很少画画/更新每个单元格）。实现jTable后我遇到了java.lang.OutOfMemoryError: Java heap space。我发现这是由于每微秒调用paint(Graphics g, JComponent c)。我不希望只在表被更新/修改的情况下一直调用此方法。有没有办法解决这个问题？

修改

我没有手动调用油漆。该表具有手动创建的UI，该UI使用setUI方法设置。我已经使用这个UI创建了可以跨越多行或多列的单元格（即将几个单元格合并在一起）。

setUI(new MultiSpanCellTableUI());

类MultiSpanCellTableUI实现了paint()方法，该方法每秒都会调用一次。

public void paint(Graphics g, JComponent c) {
    Rectangle oldClipBounds = g.getClipBounds();
    Rectangle clipBounds = new Rectangle(oldClipBounds);
    int tableWidth = table.getColumnModel().getTotalColumnWidth();
    clipBounds.width = Math.min(clipBounds.width, tableWidth);
    g.setClip(clipBounds);

    int firstIndex = table.rowAtPoint(new Point(0, clipBounds.y));
    int lastIndex = table.getRowCount() - 1;

    Rectangle rowRect = new Rectangle(0, 0, tableWidth,
            table.getRowHeight() + table.getRowMargin());
    rowRect.y = firstIndex * rowRect.height;

    for (int index = firstIndex; index <= lastIndex; index++) {
        if (rowRect.intersects(clipBounds)) {
            paintRow(g, index);
        }
        rowRect.y += rowRect.height;
    }
    g.setClip(oldClipBounds);
}

private void paintRow(Graphics g, int row) {    
    System.out.println("paintRow called");

    Rectangle rect = g.getClipBounds();
    boolean drawn = false;

    AttributiveCellTableModel tableModel = (AttributiveCellTableModel) table
            .getModel();
    CellSpan cellAtt = (CellSpan) tableModel.getCellAttribute();
    int numColumns = table.getColumnCount();

    for (int column = 0; column < numColumns; column++) {
        Rectangle cellRect = table.getCellRect(row, column, true);
        int cellRow, cellColumn;
        if (cellAtt.isVisible(row, column)) {
            cellRow = row;
            cellColumn = column;
        } else {
            cellRow = row + cellAtt.getSpan(row, column)[CellSpan.ROW];
            cellColumn = column
                    + cellAtt.getSpan(row, column)[CellSpan.COLUMN];
        }
        if (cellRect.intersects(rect)) {
            drawn = true;
            System.out.println("paintCell called!");
            paintCell(g, cellRect, cellRow, cellColumn);
        } else {
            if (drawn)
                break;
        }
    }

}

private void paintCell(Graphics g, Rectangle cellRect, int row, int column) {
    int spacingHeight = table.getRowMargin();
    int spacingWidth = table.getColumnModel().getColumnMargin();

    Color c = g.getColor();
    g.setColor(table.getGridColor());
    g.drawRect(cellRect.x, cellRect.y, cellRect.width - 1,
            cellRect.height - 1);
    g.setColor(c);

    cellRect.setBounds(cellRect.x + spacingWidth / 2, cellRect.y
            + spacingHeight / 2, cellRect.width - spacingWidth,
            cellRect.height - spacingHeight);

    if (table.isEditing() && table.getEditingRow() == row
            && table.getEditingColumn() == column) {
        Component component = table.getEditorComponent();
        component.setBounds(cellRect);
        component.validate();
    } else {
        TableCellRenderer renderer = table.getCellRenderer(row, column);
        Component component = table.prepareRenderer(renderer, row, column);

        if (component.getParent() == null) {
            rendererPane.add(component);
        }
        rendererPane.paintComponent(g, component, table, cellRect.x,
                cellRect.y, cellRect.width, cellRect.height, true);
    }
}

由于它每隔一秒被调用一段时间后OutOfMemoryError发生。我只需要在更新单元格中的内容时重新绘制单元格，并且可以轻松获取该信息。但是，如何根据该信息限制对paint()的调用？

Answer 1

不确定为什么需要

1）paint()绘画，请JTable's Cel l中的哪种类型的组件，如果有一些JComponent，你必须覆盖paintComponent()而不是paint()

2）在较大的JTable

中执行自定义绘画的设计不佳

3）你必须看Renderer，如果你使用一些颜色进行绘画，那么最好是prepareRenderer

4）JTable默认返回JLabel，在那里你可以设置Icon instaead prerform一些自定义绘画

5）也许可以帮助您JTable's表现Christmas Tree Applications

Answer 2

如果上面没有发布代码，我认为您在paint()组件上强制JTable。不需要在paint()对象上调用JTable。要自定义单元格绘制，请改用TableCellRenderer。

public class MyCellRenderer extends JLabel implements TableCellRenderer {
    public Component getTableCellRendererComponent(JTable table, Object value,
            boolean isSelected, boolean hasFocus, int rowIndex, int vColIndex) {
        if (isSelected) {
            // Is cell selected?
        }
        if (hasFocus) {
            // Does this cell have the focus
        }
        // Configure the component with the specified value, here we are using JLabel
        setText(value.toString());
        // Set tool tip if desired
        setToolTipText((String)value);
        // Since the renderer is a component, return itself
        return this;
    }
}

jTable paint（）导致java.lang.OutOfMemoryError：Java堆空间

2 个答案: