java - 当我们按下键盘上的 TAB 按钮时，如何使滚动 Pane 的滚动条随光标自动移动？

Question

我有以下代码。执行以下代码后，它显示了一个包含一个 JInternalFrame 的 JFrame，它有一个 JScrollPane 这个 JScrollPane 有一个 JPanel 有很多输入控件。由于 JPanel 的大小由于许多输入控件而比 JInternalFrame 的大小更大，所以我它是可滚动的。

import java.awt.Dimension;
import javax.swing.JDesktopPane;
import javax.swing.JFrame;
import javax.swing.JInternalFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextField;

public class InterfaceDesign {

    public static void main(String args[]) {
        InterfaceDesign id = new InterfaceDesign();
        id.getPnlProjectDetail("My Project");
    }

    public void getPnlProjectDetail(String strProjectName) {
        JPanel pnlPjDetail = new JPanel();
        JScrollPane scrPjDetail;
        pnlPjDetail.setLayout(null);
        pnlPjDetail.setBounds(0, 0, 400, 400);
        JFrame frmtest = new JFrame();
        JInternalFrame interFrame = new JInternalFrame();
        interFrame.setBounds(0, 0, 280, 180);

        frmtest.setBounds(1, 1, 300, 200);
        pnlPjDetail.setPreferredSize(new Dimension(400, 400));

        JLabel lblFirstName = new JLabel("First Name");
        JLabel lblLastName = new JLabel("Last Name");
        JLabel lblAddress = new JLabel("Address");
        JLabel lblCity = new JLabel("City");
        JLabel lblZipCode = new JLabel("Zip Code");
        JLabel lblPhone = new JLabel("Phone");
        JLabel lblEmailID = new JLabel("Emain Id");

        JTextField tfFirstName = new JTextField();
        JTextField tfLastName = new JTextField();
        JTextField tfAddress = new JTextField();
        JTextField tfCity = new JTextField();
        JTextField tfZipCode = new JTextField();
        JTextField tfPhone = new JTextField();
        JTextField tfEmailID = new JTextField();

        lblFirstName.setBounds(25, 55, 85, 20);
        tfFirstName.setBounds(25, 85, 85, 20);
        pnlPjDetail.add(lblFirstName);
        pnlPjDetail.add(tfFirstName);

        lblLastName.setBounds(25, 115, 85, 20);
        tfLastName.setBounds(25, 145, 85, 20);
        pnlPjDetail.add(lblLastName);
        pnlPjDetail.add(tfLastName);

        lblAddress.setBounds(25, 175, 85, 20);
        tfAddress.setBounds(25, 205, 85, 20);
        pnlPjDetail.add(lblAddress);
        pnlPjDetail.add(tfAddress);

        lblCity.setBounds(25, 235, 85, 20);
        tfCity.setBounds(25, 265, 85, 20);
        pnlPjDetail.add(lblCity);
        pnlPjDetail.add(tfCity);

        lblZipCode.setBounds(25, 295, 85, 20);
        tfZipCode.setBounds(25, 325, 85, 20);
        pnlPjDetail.add(lblZipCode);
        pnlPjDetail.add(tfZipCode);

        lblPhone.setBounds(25, 355, 85, 20);
        tfPhone.setBounds(25, 385, 85, 20);
        pnlPjDetail.add(lblPhone);
        pnlPjDetail.add(tfPhone);

        lblEmailID.setBounds(25, 415, 85, 20);
        tfEmailID.setBounds(25, 445, 85, 20);
        pnlPjDetail.add(lblEmailID);
        pnlPjDetail.add(tfEmailID);

        scrPjDetail = new JScrollPane(pnlPjDetail);

        scrPjDetail.setAutoscrolls(true);

        //frmtest.setContentPane(scrProjectDetail);
        interFrame.setContentPane(scrPjDetail);
        JDesktopPane dpane = new JDesktopPane();
        interFrame.setVisible(true);
        dpane.add(interFrame);

        //frmtest.getLayeredPane().add(interFrame);
        frmtest.setContentPane(dpane);
        //frmtest.add(scrProjectDetail);
        frmtest.setVisible(true);
        frmtest.setResizable(false);
        frmtest.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        //return pnlPjDetail;
    }
}

我需要您的指导来解决以下问题/疑问

1. 当我们按下键盘上的 TAB 按钮时，光标会从一个文本框移动到另一个文本框，但 ScrollBar(此处为垂直滚动条)不会随着光标移动到下方的输入字段而自动移动 那么如何使滚动条移动当它向下或向上移动时，它本身是否与光标一起移动？
2. 由于这是一个演示代码，是否可以将两个 JscrollPane 并排添加到 JInterNalFrame 中？
3. 是否需要用户JDesktopPane 将JInternalFrame 添加到JFrame 中？即我们不能按如下方式添加 JInternalFrame 是真的吗 <JFrame>.getContentPane.add(<JInternalFrame>);

Answer 1

简单的任务，令人惊讶的古怪解决方案 - 就个人而言，我认为每个必须依赖焦点的应用程序代码解决方案都是古怪的;-)

无法提出任何不依赖于焦点的东西:通过不需要在表单上的每个组件上都使用 focusListener，只会稍微提高可维护性。相反，向 KeyboardFocusManager 注册一个 PropertyChangeListener 并在收到关于其 PermanentFocusOwner 属性更改的通知时进行滚动

public static class FocusDrivenScroller implements PropertyChangeListener {

    private JComponent parent;

    public FocusDrivenScroller(JComponent parent) {
        this.parent = parent;
    }

    @Override
    public void propertyChange(PropertyChangeEvent evt) {
        Component focused = (Component) evt.getNewValue();
        if (focused == null || !SwingUtilities.isDescendingFrom(focused, parent)) return;
        parent.scrollRectToVisible(focused.getBounds());
    }

}

要在应用程序代码中使用，请使用 JScrollPane 中的表单进行实例化

public void buildAndShowDetailsFrame(String strProjectName) {
    // the container to scroll such that a focused child
    // is visible when gaining focus
    JPanel detailsForm = new JPanel();
    KeyboardFocusManager.getCurrentKeyboardFocusManager()
        .addPropertyChangeListener("permanentFocusOwner", 
                new FocusDrivenScroller(detailsForm));

    // choose and use an appropriate LayoutManager
    // note: this is only an example!
    // real-world requirements most probably need a stronger one
    detailsForm.setLayout(new BoxLayout(detailsForm, BoxLayout.PAGE_AXIS));
    // quick fill with stuff 
    String[] labels = {"First Name", "Last Name", 
            "Address", "City", "Zip Code", "Phone", "Emain Id"};
    for (String string : labels) {
        detailsForm.add(new JLabel(string));
        detailsForm.add(new JTextField());
    }
    JFrame frame = new JFrame();
    frame.add(new JScrollPane(detailsForm));
    frame.pack();
    // force scrollbar to appear
    frame.setSize(frame.getWidth(), frame.getHeight()/2);
    frame.setVisible(true);
    frame.setResizable(false);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}

除了这个方法的第一行之外，它只是 OP 代码的缩短版本(用来引诱他/她使用适当的 LayoutManager :-)