滚动到焦点文本字段

Question

所以，我在滚动窗格中有一堆文本字段。 当用户聚焦底部的最后一个文本字段时，会添加更多文本字段。 我的问题是，如何使滚动窗格滚动到聚焦的文本字段？ 我的意思是，用户将按 TAB 或 ENTER 键跳转到下一个文本字段，但如果不滚动自己将无法看到它。 当最后一个文本字段具有焦点时，我可以模拟按下向下箭头或 PageDown，但这会很难看，即使它会做我需要的。

我通过搜索找到了类似的东西，但我无法让它发挥作用。

public void focusGained(FocusEvent e) {
            currentview = t1;
            int cons = i - 1;
             Rectangle r = new Rectangle(t1.getX(), t1.getY(), 1, 1);
            jScrollPane1.scrollRectToVisible(r);
            if (t1.getName().equals("prod" + cons)) {

                newproduct();
            };

        }

Answer 1

出现两件事。

首先， JTextField#scrollRectToVisible已被覆盖，并且与其他组件有些不同……令人讨厌。

其次，您需要转换相对于其父级的字段位置，然后使用父级的scrollRectToVisible方法，例如...

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Rectangle;
import java.awt.event.FocusAdapter;
import java.awt.event.FocusEvent;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class ScrollFocusedField {

    public static void main(String[] args) {
        new ScrollFocusedField();
    }

    public ScrollFocusedField() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                FocusAdapter fh = new FocusAdapter() {

                    @Override
                    public void focusGained(FocusEvent e) {
                        JComponent comp = (JComponent) e.getComponent();
                        System.out.println("FocusGained");
                        Rectangle bounds = comp.getBounds();
                        bounds.setLocation(SwingUtilities.convertPoint(comp, bounds.getLocation(), comp.getParent()));

                        JComponent parent = (JComponent) comp.getParent();
                        parent.scrollRectToVisible(comp.getBounds());
                    }

                };

                JPanel panel = new JPanel(new GridBagLayout());
                GridBagConstraints gbc = new GridBagConstraints();
                for (int index = 0; index < 100; index++) {
                    gbc.fill = GridBagConstraints.NONE;
                    gbc.weightx = 0;
                    gbc.gridx = 0;
                    gbc.gridy = index;
                    panel.add(new JLabel(Integer.toString(index)), gbc);

                    JTextField field = new JTextField();
                    field.addFocusListener(fh);
                    gbc.fill = GridBagConstraints.HORIZONTAL;
                    gbc.weightx = 1;
                    gbc.gridx = 1;
                    panel.add(field, gbc);
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new JScrollPane(panel));
                frame.setSize(200, 400);
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

}

Answer 2

检出FormScroller 。 这是一个简单的类，可用于确保在您选择组件时可以看到该组件。 FormScroller可以与任何滚动窗格一起使用，并且无需将FocusListeners添加到表单上的每个组件。

它提供了一些选项，使您可以精确控制滚动的工作方式。

Answer 3

我用自定义焦点遍历策略解决了这个问题。 它包装了容器的原始遍历策略，并在请求下一个或上一个组件时对滚动请求进行排队：

private static class FocusTraversalPolicyAdapter extends FocusTraversalPolicy {
    FocusTraversalPolicy focusTraversalPolicy;

    FocusTraversalPolicyAdapter(FocusTraversalPolicy focusTraversalPolicy) {
        this.focusTraversalPolicy = focusTraversalPolicy;
    }

    @Override
    public Component getComponentAfter(Container container, Component component) {
        var nextComponent = focusTraversalPolicy.getComponentAfter(container, component);

        scrollToVisible(nextComponent);

        return nextComponent;
    }

    @Override
    public Component getComponentBefore(Container container, Component component) {
        var previousComponent = focusTraversalPolicy.getComponentBefore(container, component);

        scrollToVisible(previousComponent);

        return previousComponent;
    }

    @Override
    public Component getFirstComponent(Container container) {
        return focusTraversalPolicy.getFirstComponent(container);
    }

    @Override
    public Component getLastComponent(Container container) {
        return focusTraversalPolicy.getLastComponent(container);
    }

    @Override
    public Component getDefaultComponent(Container container) {
        return focusTraversalPolicy.getDefaultComponent(container);
    }

    void scrollToVisible(Component component) {
        var parent = component.getParent();

        if (parent instanceof JComponent) {
            SwingUtilities.invokeLater(() -> {
                ((JComponent)parent).scrollRectToVisible(SwingUtilities.convertRectangle(parent, component.getBounds(), parent));
            });
        }
    }
}

请注意，这确实依赖于现有行为，理论上将来可能会中断。

Answer 4

根据我之前的回答，一种更简单且可能更可靠的方法是定义自定义键盘焦点处理程序。 每当组件接收到输入焦点时，管理器就会调度事件并将组件滚动到视图中：

public class ScrollingKeyboardFocusManager extends DefaultKeyboardFocusManager {
    @Override
    public boolean dispatchEvent(AWTEvent event) {
        var dispatched = super.dispatchEvent(event);

        if (dispatched && event.getID() == FocusEvent.FOCUS_GAINED) {
            var component = (Component)event.getSource();
            var parent = component.getParent();

            if (parent instanceof JComponent) {
                ((JComponent)parent).scrollRectToVisible(SwingUtilities.convertRectangle(parent, component.getBounds(), parent));
            }
        }

        return dispatched;
    }
}

可以按如下方式安装焦点管理器：

KeyboardFocusManager.setCurrentKeyboardFocusManager(new ScrollingKeyboardFocusManager());