java - 带有卡住和可滚动组件的 JScrollPane 列标题

Question

我有一个 JScrollPane ，其列标题由多个组件组成。其中一个组件需要静态定位，而其他组件需要像平常一样滚动。

我唯一能想到做的就是向滚动条添加一个监听器，它设置卡住组件的位置，如下所示:

frozenHeader.setLocation(scrollViewport.getVisibleRect().getLocation()).  

但是，直到滚动条不再长时间滚动后，位置才会真正更新，所以它看起来相当没有吸引力。是的，我尝试过在 frozenHeader 及其父级上调用 revalidate()，然后调用 repaint()。

这是一个重现我正在谈论的内容的示例:

import java.awt.Color;
import java.awt.Dimension;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;

/**
 *
 * @author brian
 */
public class TestScroll extends JFrame {
    private JScrollPane scrollPane;
    private JPanel viewport;
    private JPanel colHeader;

    // This should be frozen
    private JPanel frozenHeader;
    // This should scroll
    private JPanel scrollHeader;

    public TestScroll() {
        this.setSize(new Dimension(500, 400));
        this.setResizable(false);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        // Set up the scroll pane
        scrollPane = new JScrollPane();
        viewport = new JPanel();
        viewport.setPreferredSize(new Dimension(1000, 400));
        scrollPane.setViewportView(viewport);

        // Set up the scroll panes column header
        colHeader = new JPanel(new GridBagLayout());
        frozenHeader = new JPanel();
        // Width is equal to the frame's width, as it should stay in the same location
        frozenHeader.setPreferredSize(new Dimension(500, 30));
        frozenHeader.setBackground(Color.RED);

        scrollHeader = new JPanel();
        // Width equal to viewportview's as it should scroll
        scrollHeader.setPreferredSize(new Dimension(1000, 30));
        scrollHeader.setBackground(Color.BLUE);
        JLabel label = new JLabel("Text");
        scrollHeader.add(label);

        GridBagConstraints c = new GridBagConstraints();
        c.anchor = GridBagConstraints.WEST;
        c.gridx = 0;
        c.gridy = 0;
        colHeader.add(frozenHeader, c);
        c.gridy = 1;
        colHeader.add(scrollHeader, c);
        scrollPane.setColumnHeaderView(colHeader);

        add(scrollPane);
    }

    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new TestScroll().setVisible(true);
            }
        });
    }
}

我希望 frozenHeader(红色面板)始终位于屏幕中央，而不是滚动到屏幕外，并且 scrollHeader(蓝色面板)像示例中那样继续滚动。

为了添加更多上下文，我之所以不简单地将 scrollHeader 放在视口(viewport)中，或者将 frozenHeader 移出列标题并简单地将其放置在 JScrollPane 上方，是因为我的实际应用程序中的 JScrollPane 有一个左上角面板，其高度与列标题相同。由于应用程序的性质，我需要利用所有的屏幕空间。

任何有关如何实现这一目标的建议将不胜感激!

Answer 1

"I want the Red Panel to always be centered in the screen, instead of scrolling off the screen."

问题在于您正在设置columnHeaderView。这可以很容易地完成，只需将 colHeader 面板设置为独立实体，并且不设置 columnHeaderView

    colHeader = new JPanel(new FlowLayout(FlowLayout.CENTER, 0, 0));
    colHeader.add(frozenHeader);
    JPanel panelForScrollPaneAndScrollHeader = new JPanel(new BorderLayout());
    panelForScrollPaneAndScrollHeader.add(scrollHeader, BorderLayout.NORTH);
    panelForScrollPaneAndScrollHeader.add(scrollPane, BorderLayout.CENTER);

    add(colHeader, BorderLayout.NORTH);
    add(panelForScrollPaneAndScrollHeader, BorderLayout.CENTER);

这是执行此操作的结果

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.FlowLayout;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;

public class TestScroll1 extends JFrame{
    private JScrollPane scrollPane;
    private JPanel viewport;
    private JPanel colHeader;
    private JPanel frozenHeader;
    private JPanel scrollHeader;

    public TestScroll1() {
        frozenHeader = new JPanel();
        frozenHeader.setPreferredSize(new Dimension(500, 30));
        frozenHeader.setBackground(Color.RED);

        scrollHeader = new JPanel();
        scrollHeader.setPreferredSize(new Dimension(1000, 30));
        scrollHeader.setBackground(Color.BLUE);

        scrollPane = new JScrollPane();
        viewport = new JPanel();
        viewport.setPreferredSize(new Dimension(1000, 400));
        scrollPane.setViewportView(viewport);


        colHeader = new JPanel(new FlowLayout(FlowLayout.CENTER, 0, 0));
        colHeader.add(frozenHeader);
        JPanel panelForScrollPaneAndScrollHeader = new JPanel(new BorderLayout());
        panelForScrollPaneAndScrollHeader.add(scrollHeader, BorderLayout.NORTH);
        panelForScrollPaneAndScrollHeader.add(scrollPane, BorderLayout.CENTER);
        add(colHeader, BorderLayout.NORTH);
        add(panelForScrollPaneAndScrollHeader, BorderLayout.CENTER);


        setSize(new Dimension(500, 400));
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLocationRelativeTo(null);

    }

    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                new TestScroll1().setVisible(true);
            }
        });
    }
}