显然我对SpringLayout有些不了解。我正在尝试创建一个类，JPanel 的扩展，它允许我添加组件并让它们垂直显示，宽度都相同。
我的 JPanel 扩展会将其 LayoutManager 设置为使用 SpringLayout，每次添加组件时，它都会放入 SpringLayout 约束以将其附加到第一个组件的面板上，然后每个组件附加到前一个组件。
首先，这里有一个Oracle编写的使用SpringLayout的示例，我将其更改为垂直而不是水平放置组件：
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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的要求的理解，我写了以下内容：
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);
}
}
这里有一个小程序来测试它：
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);
}
}
组件显示在面板顶部的彼此顶部。我认为在添加时设置每个组件的约束以将每个组件的北端连接到前一个组件的南边缘，将按添加的顺序将它们垂直排列。我有finishedAdding()方法，这样我就可以包装最后一个组件与其容器的连接，如 https://docs.oracle.com/javase/tutorial/uiswing/layout/spring.html 的"如何使用 SpringLayout"教程中所述，以及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叠加，但(两个)演示组件垂直相邻。我是否能够满足我最初的愿望，即让垂直组件在面板中拉伸成相同的尺寸？
你需要改变
springLayout.putConstraint(topConstraint, comp, padding, SpringLayout.NORTH, northComponent);
自
springLayout.putConstraint(NORTH, comp, padding, topConstraint, northComponent);
正如Hitesh指出的那样，您在add方法中将参数交换为SpringLayout.putConstraint。 文档指出：
public void putConstraint(String e1, Component c1, int pad, String e2, Component c2)。
参数：e1- 从属的边缘c1- 从属的分量>pad- 从属和锚之间的固定距离e2- 锚的边缘c2- 锚的分 量
前两个参数是"依赖"，即要定位的组件。 最后两个参数是"锚点"，即所定位组件将依赖的另一个组件(或容器)。
但这并不是问题的全部。 要使所有组件的宽度相同，您需要使用使用 Spring.max 构建的 Spring 聚合它们的所有高度。
基于组件的 Spring 是一个"实时"对象：每当它们在相应组件中发生变化时，确切的最小值、首选值和最大值就会发生变化。 因此，所有这些基于组件的 Spring 对象的最大值将是您要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，在您的add方法中，您只需要调用一次即可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"弹簧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，为了确保每个组件拉伸以填充容器的宽度，我们将其东西两侧都连接到容器上。
对于它的价值，你实际上并不需要SpringLayout。 Box可以做你想做的事，不需要专门的类：
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);
}
这是我最终想到的：
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);
}
}
而电流测试仪：
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);
}
}
这些组件以添加到面板的最宽组件的宽度(按首选大小)显示。按钮不会随面板拉伸，但文本字段可以 - 我曾以为设置按钮的最大大小并添加和 EAST 方向约束会拉伸它们，但似乎没有，我现在不需要它。