Question

我在Swing中编写了一个简单的输入图。我使用boxLayout创建一个简单的用户输入GUI。问题是在所有标签的JPanel和JTextFields的JPanel之间创建一个水平支柱会导致整个面板向下移动（奇怪）这是整个面板：

private JPanel secondCard() {

    //main panel. set the boxlayout
    secondCard = new JPanel();
    secondCard.setLayout(new BoxLayout(secondCard,BoxLayout.Y_AXIS));

    // create vertical strut for looks
    secondCard.add(Box.createVerticalStrut(20));

    // create title. center it.
    JLabel title = new JLabel("Configure main network parameters "); 
    title.setAlignmentX(CENTER_ALIGNMENT);
    secondCard.add(title);

    // create vertical strut for looks
    secondCard.add(Box.createVerticalStrut(20));

    // create panel for the description labels
    JPanel labelPanel = new JPanel();
    labelPanel.setLayout(new BoxLayout(labelPanel,BoxLayout.Y_AXIS));
    labelPanel.setAlignmentX(LEFT_ALIGNMENT);

    JLabel inPut =new JLabel("number of inputs");
    inPut.setAlignmentX(LEFT_ALIGNMENT);
    labelPanel.add(inPut);

    inPut =new JLabel("number of outputs");
    inPut.setAlignmentX(LEFT_ALIGNMENT);
    labelPanel.add(inPut);

    inPut =new JLabel("number of layers");
    inPut.setAlignmentX(LEFT_ALIGNMENT);
    labelPanel.add(inPut);

    JPanel textFieldPanel = new JPanel();
    textFieldPanel.setLayout(new BoxLayout(textFieldPanel,BoxLayout.Y_AXIS));
    textFieldPanel.setAlignmentX(LEFT_ALIGNMENT);

    JTextField inputTextField = new JTextField();
    inputTextField.setAlignmentX(LEFT_ALIGNMENT);
    textFieldPanel.add(inputTextField);
    inputTextField.setMinimumSize(new Dimension(0,0));

    inputTextField = new JTextField();
    inputTextField.setAlignmentX(LEFT_ALIGNMENT);
    textFieldPanel.add(inputTextField);
    inputTextField.setMinimumSize(new Dimension(0,0));

    inputTextField = new JTextField();
    inputTextField.setAlignmentX(LEFT_ALIGNMENT);
    textFieldPanel.add(inputTextField);
    inputTextField.setMinimumSize(new Dimension(0,0));

    textFieldPanel.setMaximumSize(new Dimension(50, labelPanel.getMaximumSize().height));

    JPanel inputPanel = new JPanel();
    inputPanel.setLayout(new BoxLayout(inputPanel,BoxLayout.X_AXIS));
    inputPanel.setAlignmentX(CENTER_ALIGNMENT);

    inputPanel.add(labelPanel);

    //this is the problem strut!! it causes inputPanel to shift downwards 
    inputPanel.add(Box.createHorizontalStrut(20));

    inputPanel.add(textFieldPanel);

    secondCard.add(inputPanel);

    return secondCard;
}

没有支柱它看起来像： enter image description here

用strut看起来（我知道我很喜欢图片编辑）：

enter image description here

Answer 1

您正在向Box添加BoxLayout支柱。

正如javadoc所述，createHorizontalStrut(int width)：

创建一个不可见的固定宽度组件。在一个水平的盒子里，你通常使用此方法强制之间的一定量的空间两个组件。在垂直框中，您可以使用此方法强制使用该框至少是指定的宽度。隐形组件除非有足够的空间，否则没有高度，在这种情况下需要它的可用空间份额，就像任何其他组件一样没有最大高度。

因此，它填充了标题JLabel和JPanel底部之间的高度。

您可能需要考虑使用Box.createRigidArea(new Dimension(20, height))，其中可以指定高度或将其设置为labelPanel的高度。

或者，您可以重新考虑JPanel的布局 - 看看visual guide。

为了将来参考，如果您无法理解Swing布局，请尝试向您不确定的LineBorder添加彩色JComponent。在这种情况下，Box struts不是JComponent而是Component s，因此您必须将它们放入JPanel，但这至少会显示出来您在顶级JPanel中占用的每个组件的空间。

Answer 2

使用Cardlayout进行向导逻辑
将JLabel(Configure ...., JLabel.CENTER)添加到BorderLayout.NORTH
将JPanel与JButtons一起放入BorderLayout.SOUTH
将带有SpringLayout，GridLayout或GridBagLayout的JPanel放入BorderLayout.CENTER
Top-Level Container已经实施BorderLayout，然后没有理由重新定义BorderLayout
上述步骤称为NestedLayout
使用JComponents，GridBagLayout或今天SpringLayout将所有MigLayout置于JPanel之内，但为什么要打扰

Answer 3

嵌套布局的示例，一个使用BorderLayout，FlowLayout（JPanel的默认值）和GridBagLayout：

import java.awt.BorderLayout;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.util.HashMap;
import java.util.Map;

import javax.swing.*;

public class LayoutFoo {
   private static final String TITLE = "Configure Main Foobar Parameters";
   private static final String[] LABEL_TEXTS = {
      "Number of Spams", "Number of Frapzats", "Number of Zignuts"
   };
   private static final int TEXTFIELD_SIZE = 10;
   private static final Insets WEST_INSETS = new Insets(5, 5, 5, 10);
   private static final Insets EAST_INSETS = new Insets(5, 10, 5, 5);
   private static final int EB_GAP = 5;
   private Map<String, JTextField> textFieldMap = new HashMap<String, JTextField>();

   public JPanel getConfigFooPanel() {
      JPanel textFieldPanel = new JPanel(new GridBagLayout());
      for (int i = 0; i < LABEL_TEXTS.length; i++) {
         addTextAndField(textFieldPanel, LABEL_TEXTS[i], i);
      }

      int blVertGap = 20;
      JPanel borderLayoutPanel = new JPanel(new BorderLayout(0, blVertGap));
      borderLayoutPanel.setBorder(BorderFactory.createEmptyBorder(EB_GAP, EB_GAP,
            EB_GAP, EB_GAP));
      JLabel titleLabel = new JLabel(TITLE, JLabel.CENTER);
      borderLayoutPanel.add(titleLabel, BorderLayout.PAGE_START);
      borderLayoutPanel.add(textFieldPanel, BorderLayout.CENTER);

      JPanel outerWrapperFlowPanel = new JPanel();
      outerWrapperFlowPanel.add(borderLayoutPanel);

      return outerWrapperFlowPanel;      
   }

   public String getFieldText(String labelText) {
      JTextField field = textFieldMap.get(labelText);
      if (field == null) {
         return ""; // ?? throw exception
      } else {
         return field.getText();
      }
   }

   private void addTextAndField(JPanel panel, String text, int i) {
      JLabel label = new JLabel(text, JLabel.LEFT);
      JTextField textField = new JTextField(TEXTFIELD_SIZE);
      textFieldMap.put(text, textField);
      GridBagConstraints gbc = new GridBagConstraints();
      gbc.gridx = 0;
      gbc.gridy = i;
      gbc.gridwidth = 1;
      gbc.gridheight = 1;
      gbc.weightx = 1.0;
      gbc.weighty = 1.0;
      gbc.fill = GridBagConstraints.HORIZONTAL;
      gbc.anchor = GridBagConstraints.WEST;
      gbc.insets = WEST_INSETS;
      panel.add(label, gbc);

      gbc.gridx = 1;
      gbc.anchor = GridBagConstraints.EAST;
      gbc.insets = EAST_INSETS;
      panel.add(textField, gbc);
   }

   private static void createAndShowGui() {
      JFrame frame = new JFrame("LayoutFoo");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.getContentPane().add(new LayoutFoo().getConfigFooPanel());
      frame.pack();
      frame.setLocationRelativeTo(null);
      frame.setVisible(true);
   }

   public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
         public void run() {
            createAndShowGui();
         }
      });
   }
}

BoxLayout误解了支柱

3 个答案: