如何使用SpringLayout垂直排列組件-有解無憂

顯然我對 SpringLayout 有一些不明白的地方。我正在嘗試創建一個類，即 JPanel 的擴展，它允許我添加組件并讓它們垂直顯示，寬度相同。

我對 JPanel 的擴展會將其 LayoutManager 設定為使用 SpringLayout，并且每次添加組件時，它都會放入 SpringLayout 約束以將其附加到第一個組件的面板，然后將每個組件附加到前一個組件。

首先，這是一個 Oracle 撰寫的使用 SpringLayout 的示例，我將其更改為垂直放置組件而不是水平放置：

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import javax.swing.SpringLayout;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;
import java.awt.Container;

public class SpringDemo3
{
  /**
   * Create the GUI and show it. For thread safety, this method should be
   * invoked from the event-dispatching thread.
   */
  private static void createAndShowGUI()
  {
    // Create and set up the window.
    JFrame frame = new JFrame("SpringDemo3");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    // Set up the content pane.
    Container contentPane = frame.getContentPane();
    SpringLayout layout = new SpringLayout();
    contentPane.setLayout(layout);

    // Create and add the components.
    JLabel label = new JLabel("Label: ");
    JTextField textField = new JTextField("Text field", 15);
    contentPane.add(label);
    contentPane.add(textField);

    // Adjust constraints for the label so it's at (5,5).
    layout.putConstraint(SpringLayout.WEST, label, 5, SpringLayout.WEST, contentPane);
    layout.putConstraint(SpringLayout.NORTH, label, 5, SpringLayout.NORTH, contentPane);

    // Adjust constraints for the text field so it's at
    // (<label's right edge>   5, 5).
//    layout.putConstraint(SpringLayout.WEST, textField, 5, SpringLayout.EAST, label);
//    layout.putConstraint(SpringLayout.EAST, textField, 5, SpringLayout.EAST, contentPane);
    layout.putConstraint(SpringLayout.NORTH, textField, 5, SpringLayout.SOUTH, label);

    // Adjust constraints for the content pane: Its right
    // edge should be 5 pixels beyond the text field's right
    // edge, and its bottom edge should be 5 pixels beyond
    // the bottom edge of the tallest component (which we'll
    // assume is textField).
    layout.putConstraint(SpringLayout.EAST, contentPane, 5, SpringLayout.EAST, textField);
    layout.putConstraint(SpringLayout.SOUTH, contentPane, 5, SpringLayout.SOUTH, textField);

    // Display the window.
    frame.pack();
    frame.setVisible(true);
  }

  public static void main(String[] args)
  {
    // Schedule a job for the event-dispatching thread:
    // creating and showing this application's GUI.
    javax.swing.SwingUtilities.invokeLater(new Runnable()
    {
      public void run()
      {
        createAndShowGUI();
      }
    });
  }
}

根據我對 SpringLayout 要求的理解，我撰寫了以下內容：

import java.awt.Component;
import java.awt.LayoutManager;
import java.util.ArrayList;

import javax.swing.JPanel;
import javax.swing.SpringLayout;

import static javax.swing.SpringLayout.NORTH;
import static javax.swing.SpringLayout.EAST;
import static javax.swing.SpringLayout.SOUTH;
import static javax.swing.SpringLayout.WEST;

public class OneWidthPanel extends JPanel
{
  private static final long serialVersionUID = 1L;
  
  private int padding = 5;
  SpringLayout springLayout = new SpringLayout();
  
  public OneWidthPanel() { super(); setLayout(springLayout); }
  public OneWidthPanel(boolean isDoubleBuffered) { super(isDoubleBuffered); }
  public OneWidthPanel(LayoutManager layout) { throw new IllegalArgumentException("Cannot set a layout manager on the OneWidthPanel class"); }
  public OneWidthPanel(LayoutManager l, boolean isDoubleBuffered) { throw new IllegalArgumentException("Cannot set a layout manager on the OneWidthPanel class"); }
  
  private ArrayList<Component> componentList = new ArrayList<>();
  
  @Override
  public Component add(Component comp)
  {
    super.add(comp);
    
    componentList.add(comp);
    int listSize = componentList.size();
    
    String topConstraint;
    Component northComponent;
    if (listSize == 1)
    {
      topConstraint = NORTH;
      northComponent = this;
    }
    else
    {
      topConstraint = SOUTH;
      northComponent = componentList.get(listSize - 2);
    }

    springLayout.putConstraint(topConstraint, northComponent, padding, SpringLayout.NORTH, comp);
    springLayout.putConstraint(WEST, this, padding, WEST, comp);
    springLayout.putConstraint(EAST, this, padding, EAST, comp);
    
    return comp;
  }
  
  public void finishedAdding()
  {
    Component lastComponent = componentList.get(componentList.size()-1);
    springLayout.putConstraint(EAST,   this, padding, EAST,  lastComponent);
    springLayout.putConstraint(SOUTH,  this, padding, SOUTH, lastComponent);
  }
}

這是一個測驗它的小程式：

import java.awt.BorderLayout;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JRadioButton;

import rcutil.layout.OneWidthPanel;

public class OneWidthPanelTester extends JFrame
{
  private static final long serialVersionUID = 1L;

  public static void main(String[] args)
  {
    OneWidthPanelTester tester = new OneWidthPanelTester();
    tester.go();
  }
  
  public void go()
  {
    OneWidthPanel panel = new OneWidthPanel();
    JButton button1 = new JButton("ONE new button");
    JButton button2 = new JButton("second b");
    JRadioButton rButton = new JRadioButton("choose me");
    
    panel.add(button1);
    panel.add(button2);
    panel.add(rButton);
    panel.finishedAdding();
    
    add(panel, BorderLayout.WEST);
    pack();
    setVisible(true);
  }

}

組件在面板頂部彼此重疊顯示。我想設定每個約束，當我添加它時，將每個組件的北端連接到前一個組件的南邊緣，將它們按照添加的順序垂直排列。正如https://docs.oracle.com/javase/tutorial/uiswing/layout/springfinishedAdding()上的“如何使用 SpringLayout”教程中所述，我有方法可以將最后一個組件與其容器的連接封裝起來。 html，并在我復制的演示程式中完成。

我不明白為什么我的組件相互重疊，但（兩個）演示組件垂直相鄰。我是否能夠滿足我最初的愿望，即讓垂直組件在面板中拉伸成相同的大小？

uj5u.com熱心網友回復：

你需要改變

springLayout.putConstraint(topConstraint, comp, padding, SpringLayout.NORTH, northComponent);

到

springLayout.putConstraint(NORTH, comp, padding, topConstraint, northComponent);

uj5u.com熱心網友回復：

正如 Hitesh 指出的那樣，您在add方法中將引數交換為 SpringLayout.putConstraints 。該檔案指出：

 public void putConstraint(String e1,
                           Component c1,
                           int pad,
                           String e2,
                           Component c2)
…

引數：
e1 - 依賴的邊緣 - 依賴
c1的組件
pad- 依賴和錨點之間的固定距離
e2- 錨點的邊緣 - 錨點
c2的組件

前兩個引數是“從屬”，即您要定位的組件。最后兩個引數是“anchor”——即被定位的組件將依賴的另一個組件（或容器）。

但這不是問題的全部。要使所有組件具有相同的寬度，您需要使用使用Spring.max構建的Spring聚合它們的所有高度。

基于組件的Spring是一個“活動”物件：確切的最小值、首選值和最大值在相應組件中發生變化時都會發生變化。因此，所有這些基于組件的 Spring 物件的最大值將是您要應用于所有這些物件的寬度。

首先將組件的寬度保持在私有欄位中：

private Spring width = Spring.constant(0);

然后，在您的add方法中，您只需要一次呼叫putConstraints. 暫時不要附加組件的水平尺寸：

springLayout.putConstraint(NORTH, comp, padding, topConstraint, northComponent );
width = Spring.max(width, Spring.width(comp));

最后，在中finishedAdding，使用那個“智能”Spring 作為容器的寬度和每個組件的寬度。

public void finishedAdding()
{
  Component lastComponent = componentList.get(componentList.size()-1);
  springLayout.putConstraint(EAST,   this, width,   WEST,  this);
  springLayout.putConstraint(SOUTH,  this, padding, SOUTH, lastComponent);

  // Make every component's width fill this container.
  for (Component comp : componentList) {
    springLayout.putConstraint(WEST, comp, 0, WEST, this);
    springLayout.putConstraint(EAST, comp, width, WEST, this);
  }
}

首先，我們將容器的寬度系結到所有組件的最大寬度（并將其高度系結到最后一個組件）。然后，為了確保每個組件都拉伸以填充容器的寬度，我們將其東側和西側都附加到容器上。

對于它的價值，您實際上并不需要 SpringLayout 。 Box可以做你想做的事，而不需要專門的課程：

JButton button1 = new JButton("ONE new button");
JButton button2 = new JButton("second b");
JRadioButton rButton = new JRadioButton("choose me");

int padding = 5;

Box panel = Box.createVerticalBox();
panel.add(button1);
panel.add(Box.createVerticalStrut(padding));
panel.add(button2);
panel.add(Box.createVerticalStrut(padding));
panel.add(rButton);

for (Component comp : panel.getComponents()) {
    Dimension size = comp.getMaximumSize();
    size.width = Integer.MAX_VALUE;
    comp.setMaximumSize(size);
}

uj5u.com熱心網友回復：

這是我最終想到的：

import static javax.swing.SpringLayout.EAST;
import static javax.swing.SpringLayout.NORTH;
import static javax.swing.SpringLayout.SOUTH;
import static javax.swing.SpringLayout.WEST;

import java.awt.Component;
import java.awt.Dimension;
import java.awt.LayoutManager;
import java.util.ArrayList;

import javax.swing.BoxLayout;
import javax.swing.JPanel;
import javax.swing.SpringLayout;

public class OneWidthPanel extends JPanel
{
  private static final long serialVersionUID = 1L;
  
  private int padding = 5;
  SpringLayout springLayout = new SpringLayout();
  BoxLayout boxLayout = new BoxLayout(this, BoxLayout.PAGE_AXIS);
  
  public OneWidthPanel() 
  { 
    super();
    setLayout(springLayout);
  }
  public OneWidthPanel(boolean isDoubleBuffered) { super(isDoubleBuffered); }
  public OneWidthPanel(LayoutManager layout) { throw new IllegalArgumentException("Cannot set a layout manager on the OneWidthPanel class"); }
  public OneWidthPanel(LayoutManager l, boolean isDoubleBuffered) { throw new IllegalArgumentException("Cannot set a layout manager on the OneWidthPanel class"); }
  
  private ArrayList<Component> componentList = new ArrayList<>();
  
  @Override
  public Component add(Component comp)
  {
    super.add(comp);
    
    componentList.add(comp);
    int listSize = componentList.size();

    String topConstraint;
    Component northComponent;
    if (listSize == 1)
    {
      topConstraint = NORTH;
      northComponent = this;
    }
    else
    {
      topConstraint = SOUTH;
      northComponent = componentList.get(listSize - 2);
    }

    springLayout.putConstraint(NORTH, comp, padding, topConstraint, northComponent);
    springLayout.putConstraint(WEST, comp, padding, WEST, this);
//    springLayout.putConstraint(EAST, comp, padding, EAST, this);
    
    return comp;
  }
  
  public void finishedAdding()
  {
    Component lastComponent = componentList.get(componentList.size()-1);
//    springLayout.putConstraint(EAST,   this, padding, EAST,  lastComponent);
    springLayout.putConstraint(SOUTH,  this, padding, SOUTH, lastComponent);
    springLayout.putConstraint(WEST,   this, padding, WEST,  lastComponent);

    int maxComponentWidth = 0;
    int panelHeight = padding;
    
    // calculate overall height and maximum width
    for (Component component: componentList)
    {
      Dimension componentDimension = component.getPreferredSize();
      maxComponentWidth = Math.max(maxComponentWidth, componentDimension.width);
      panelHeight = panelHeight   componentDimension.height   padding;
    }
    
    // for each component, set the component width and preferred height,
    //    and set maximum width to MAX_VALUE; I was trying to get the components
    //    to stretch, but that doesn't work.
    for (Component component: componentList)
    {
      Dimension componentDimension = component.getPreferredSize();
      Dimension newD = new Dimension(maxComponentWidth, componentDimension.height);
//      Dimension maxD = new Dimension(Integer.MAX_VALUE, componentDimension.height);
      component.setPreferredSize(newD);
      component.setMinimumSize(newD);
      component.setMaximumSize(newD);
    }
    
    // set panel dimensions
    Dimension newD = new Dimension(maxComponentWidth   (padding*2), panelHeight);
    this.setPreferredSize(newD);
    this.setMinimumSize(newD);
  }
}

和當前的測驗人員：

import java.awt.BorderLayout;
import java.awt.Color;

import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JRadioButton;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;

import rcutil.layout.OneWidthPanel;

public class OneWidthPanelTester extends JFrame implements Runnable
{
  private static final long serialVersionUID = 1L;

  public static void main(String[] args)
  {
    OneWidthPanelTester tester = new OneWidthPanelTester();
    SwingUtilities.invokeLater(tester);
  }
  
  public void run()
  {
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    
    JButton button1 = new JButton("ONE new button");
    JButton button2 = new JButton("second b");
    JRadioButton rButton = new JRadioButton("choose me");
    JLabel label = new JLabel("I'm last");
    label.setBorder(BorderFactory.createLineBorder(Color.black));
    JTextField textField = new JTextField(25);
    
    OneWidthPanel panel = new OneWidthPanel();
    panel.add(button1);
    panel.add(button2);
    panel.add(rButton);
    panel.add(label);
    panel.add(textField);
    panel.finishedAdding();
    
    add(panel, BorderLayout.CENTER);
    pack();
    setVisible(true);
  }

}

這些組件以添加到面板的最寬組件的寬度（按首選大小）顯示。按鈕不會隨面板拉伸，但文本欄位會 - 我曾認為設定按鈕的最大大小并添加和 EAST 方向約束會拉伸它們，但似乎沒有，而且我不需要這就是我現在正在做的事情。

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