Question

所以我有一个大小为500x500的JFrame，我使用g.drawLine（x，y）从（0,200）到（100000,200）绘制一条线。问题是我看不到整行，因为没有滚动条。有人可以请告诉我如何在这种特殊情况下使用滚动条来查看整个行（100000,200）。

Answer 1

虽然我有usability concerns，但下面的示例说明了如Scrollable中所讨论的如何实现How to Use Scroll Panes: Implementing a Scrolling-Savvy Client接口。请特别注意getPreferredScrollableViewportSize()的结果与getPreferredSize()的结果有何不同。单位和块增量也使分页更容易。

import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Rectangle;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.Scrollable;
import javax.swing.SwingConstants;

/**
 * @see https://stackoverflow.com/a/37460185/230513
 */
public class Test {

    private void display() {
        JFrame f = new JFrame("Test");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.add(new JScrollPane(new DrawingPanel()));
        f.pack();
        f.setLocationRelativeTo(null);
        f.setVisible(true);
    }

    private static class DrawingPanel extends JPanel implements Scrollable {

        private static final int W = 100_000;
        private static final int H = 400;

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(W, H);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            g.setColor(Color.red);
            g.drawLine(0, getHeight() / 2, getWidth(), getHeight() / 2);
            g.drawLine(0, getHeight() / 4, 0, 3 * getHeight() / 4);
            g.drawLine(W - 1, getHeight() / 4, W - 1, 3 * getHeight() / 4);
        }

        @Override
        public Dimension getPreferredScrollableViewportSize() {
            return new Dimension(640, H);
        }

        @Override
        public int getScrollableUnitIncrement(Rectangle visibleRect, int orientation, int direction) {
            if (orientation == SwingConstants.HORIZONTAL) {
                return W / 10;
            } else {
                return 10;
            }
        }

        @Override
        public int getScrollableBlockIncrement(Rectangle visibleRect, int orientation, int direction) {
            if (orientation == SwingConstants.HORIZONTAL) {
                return W / 10;
            } else {
                return 10;
            }
        }

        @Override
        public boolean getScrollableTracksViewportWidth() {
            return false;
        }

        @Override
        public boolean getScrollableTracksViewportHeight() {
            return false;
        }
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(new Test()::display);
    }
}

Answer 2

你能告诉我们代码吗？由于在没有看到它的情况下很难知道，但是我认为你应该创建一个并将它添加到你的JFrame中，如下所示：

 JTextArea ta = new JTextArea(); // Example with a JTextArea,
         depends on what you have, as I said, we need to see the code

 JScrollPane sp = new JScrollPane(ta); //Add it to the component 
    needed, in your case the drawn line i guess

 jFrame.add(sp); //Add it to the frame

在添加之前，你可以操纵尺寸：

sp.setColumnHeaderView(new JLabel("header column"));

sp.setRowHeaderView(new JLabel("header row"));

sp.setPreferredSize(new Dimension(500, 300));

Java Swing中JFrame上的滚动条

2 个答案: