如何使用SpringLayout垂直排列组件

Question

显然，关于SpringLayout，我有些东西不太明白。我正在尝试创建一个类，它是JPanel的一个扩展，它允许我添加组件并让它们垂直显示，所有宽度都一样。

我对JPanel的扩展将其LayoutManager设置为使用SpringLayout，每次添加组件时，它都会在SpringLayout约束中将其附加到第一个组件的面板上，然后将每个组件添加到前一个组件。

首先，下面是一个使用SpringLayout的Oracle编写的示例，我修改了该示例将组件垂直放置，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();
      }
    });
  }
}

基于我对SpringLayout要求的理解，我编写了以下内容：

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);
  }
}

下面是一个测试它的小程序：

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);
  }

}

组件在面板顶部出现在彼此的顶部。我认为设置每个组件的约束条件，就像我添加的那样，将每个组件的北端连接到前一个组件的南边，将它们垂直地按添加的顺序排列。我有finishedAdding()方法，这样我就可以结束最后一个组件到它的容器的连接，就像在https://docs.oracle.com/javase/tutorial/uiswing/layout/spring.html的“如何使用SpringLayout”教程中告诉的那样，以及在我复制的演示程序中所做的那样。

我不明白为什么我的组件相互重叠，但是(两个)演示组件是垂直相邻的。我是否能够满足我最初的愿望，也就是让垂直组件在面板中伸展成相同的尺寸？

Answer 1

你需要改变

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

至

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

Answer 2

正如Hitesh所指出的，您在SpringLayout.putConstraints方法中将参数交换给了add。文献资料声明：

公共无效putConstraint(String e1，Component c1，int pad，String e2，Component c2) … 参数： e1 -依赖方的边缘 c1 -依赖项的组件 pad -相依与锚之间的固定距离 e2 -锚的边缘 c2 -锚的组件

前两个参数是“依赖的”-that，您想要定位的组件。最后两个参数是“锚”-that，是要定位的组件所依赖的另一个组件(或容器)。

但这不是问题的全部。要使所有组件都具有相同的宽度，您需要使用使用春天构建的Spring.max来聚合它们的所有高度。

基于组件的弹簧是一个“活动”对象:当它们在各自的组件中发生变化时，精确的最小值、首选值和最大值都会发生变化。因此，所有基于组件的Spring对象的最大值将是您希望应用于所有这些对象的宽度。

首先，将组件的宽度保留在私有字段中：

private Spring width = Spring.constant(0);

然后，在add方法中，只需要调用一个putConstraints。暂时不要附加组件的水平尺寸：

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

最后，在finishedAdding中，使用“智能”Spring作为容器的宽度和每个组件的宽度。

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，我们将容器的宽度绑定到所有组件的最大宽度(并将其高度绑定到最后一个组件)。然后，为了确保每个组件伸展以填充容器的宽度，我们将其东侧和西侧连接到容器上。

不管它的价值是什么，您实际上并不需要SpringLayout。盒可以做您想做的事情，而不需要一个专门的类：

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);
}

Answer 3

我终于想出了如下结论：

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);
  }
}

而目前的测试人员：

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);
  }

}

这些组件显示在添加到面板的最宽组件的宽度(按首选大小)。按钮不会与面板一起拉伸，但是文本字段可以--我曾经想过设置按钮的最大大小并添加和东方方向约束会拉伸它们，但它似乎没有，我现在做的事情不需要这样做。