Question

我有controlPanel（BoxLayout）：

controlPanel.setLayout(new BoxLayout(controlPanel, BoxLayout.Y_AXIS));

现在我构建两个FlowLayout并将其添加到contolPanel面板：

JPanel fromDatePanel = new JPanel(new FlowLayout());
JPanel untilDatePanel = new JPanel(new FlowLayout());

fromDatePanel.add(new JLabel("From - "));
fromDatePanel.add(new JButton("..."));
untilDatePanel.add(new JLabel("Until - "));
untilDatePanel.add(new JButton("..."));

controlPanel.add(fromDatePanel);
controlPanel.add(untilDatePanel);

我得到了这个：

enter image description here

为什么它会在布局之间产生差距？例如，如果我插入一个JButton，它可以正常工作（它插入它们没有间隙）。

如何消除两个FlowLayout之间的差距？（所以它就像蓝色的差距）

Answer 1

请参阅Using Invisible Components as Filler关于Box.createVerticalGlue()。

Answer 2

您可以使用GridBagLayout实现垂直布局（垂直居中）（并将GridBagConstraint与gridwidth=REMAINDER一起使用）：

import java.awt.FlowLayout;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class TestGridBagLayout {

    protected void initUI() {
        JFrame frame = new JFrame();
        JPanel controlPanel = (JPanel) frame.getContentPane();
        controlPanel.setLayout(new GridBagLayout());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.gridwidth = GridBagConstraints.REMAINDER;

        JPanel fromDatePanel = new JPanel(new FlowLayout());
        JPanel untilDatePanel = new JPanel(new FlowLayout());

        fromDatePanel.add(new JLabel("From - "));
        fromDatePanel.add(new JButton("..."));
        untilDatePanel.add(new JLabel("Until - "));
        untilDatePanel.add(new JButton("..."));

        controlPanel.add(fromDatePanel, gbc);
        controlPanel.add(untilDatePanel, gbc);
        frame.setSize(600, 600);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                TestGridBagLayout testMultiplePanels = new TestGridBagLayout();
                testMultiplePanels.initUI();

            }
        });
    }

}

关于添加到JButton时JPanel和BoxLayout之间的差异，这是由于getMaximumSize()的实施差异所致。 BoxLayout。 JButton会返回首选尺寸，而JPanel将返回null，BoxLayout将其解释为无限尺寸。

如果您想保留BoxLayout，可以覆盖JPanel.getMaximumSize()并返回getPreferredSize()：

import java.awt.Dimension;
import java.awt.FlowLayout;

import javax.swing.BoxLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class TestGridBagLayout {

    protected void initUI() {
        JFrame frame = new JFrame();
        JPanel controlPanel = (JPanel) frame.getContentPane();
        controlPanel.setLayout(new BoxLayout(controlPanel, BoxLayout.Y_AXIS));
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JPanel fromDatePanel = new JPanel(new FlowLayout()) {
            @Override
            public Dimension getMaximumSize() {
                return getPreferredSize();
            }
        };
        JPanel untilDatePanel = new JPanel(new FlowLayout()) {
            @Override
            public Dimension getMaximumSize() {
                return super.getMaximumSize();
            }
        };

        fromDatePanel.add(new JLabel("From - "));
        fromDatePanel.add(new JButton("..."));
        untilDatePanel.add(new JLabel("Until - "));
        untilDatePanel.add(new JButton("..."));

        controlPanel.add(fromDatePanel);
        controlPanel.add(untilDatePanel);
        frame.setSize(600, 600);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                TestGridBagLayout testMultiplePanels = new TestGridBagLayout();
                testMultiplePanels.initUI();

            }
        });
    }

}

Answer 3

enter image description here

我使用BorderLayout并且它有效。

        JPanel controlPanel = new JPanel();
        //  controlPanel.setLayout(new BoxLayout(controlPanel, BoxLayout.Y_AXIS));
        controlPanel.setLayout(new BorderLayout());

        JPanel fromDatePanel = new JPanel(new FlowLayout());
        JPanel untilDatePanel = new JPanel(new FlowLayout());

        fromDatePanel.add(new JLabel("From - "));
        fromDatePanel.add(new JButton("..."));
        untilDatePanel.add(new JLabel("Until - "));
        untilDatePanel.add(new JButton("..."));

        controlPanel.add(fromDatePanel, BorderLayout.NORTH);
        controlPanel.add(untilDatePanel, BorderLayout.CENTER);

修改-1：

您可以在每个面板中添加嵌套面板。

JPanel controlPanel = new JPanel(); controlPanel.setLayout(new BoxLayout(controlPanel, BoxLayout.Y_AXIS)); // controlPanel.setLayout(new BorderLayout()); JPanel fromDatePanel = new JPanel(new FlowLayout()); JPanel untilDatePanel = new JPanel(new FlowLayout()); JPanel thirdPnl = new JPanel(new FlowLayout()); JPanel fourthPnl = new JPanel(new FlowLayout()); JPanel thrdForthPnl = new JPanel(new BorderLayout()); fourthPnl.add(new JLabel("Fourth")); fourthPnl.add(new JButton("4.1")); thirdPnl.add(new JLabel("Third")); thirdPnl.add(new JButton("3.1")); thrdForthPnl.add(thirdPnl, BorderLayout.NORTH); thrdForthPnl.add(fourthPnl, BorderLayout.CENTER); fromDatePanel.add(new JLabel("From - ")); fromDatePanel.add(new JButton("...")); untilDatePanel.add(new JLabel("Until - ")); untilDatePanel.add(new JButton("...")); controlPanel.add(fromDatePanel, BorderLayout.NORTH); controlPanel.add(untilDatePanel, BorderLayout.CENTER); controlPanel.add(thrdForthPnl, BorderLayout.SOUTH);

嵌套布局 - BoxLayout中的FlowLayout

3 个答案: