Java AWT | SpringLayout 类

AWT(Abstract Window Toolkit) 中的 SpringLayout 类根据一组布局约束将子级布局到其关联的容器中。每个约束都由一个 Spring 对象表示，该对象控制两个组件边缘之间的垂直或水平距离。边缘可以属于容器的任何子容器，也可以属于容器本身。默认情况下， SpringLayout创建约束，使其关联的组件具有最小值、首选、最大值和实际值。

构造函数：

• SpringLayout()：用于构造一个新的 SpringLayout 类。

常用方法：

• void addLayoutComponent(Component com, Object cons)：如果约束是SpringLayout.Constraints的一个实例，则将约束与指定的组件相关联。
• getLayoutAlignmentX(Container c)：用于返回 0.5f（居中）。
• getLayoutAlignmentY(Container c)：用于返回 0.5f（居中）。
• getConstraint((String edgeName, Component c)：返回控制组件指定边缘与其父对象上边缘或左边缘之间距离的弹簧。
• getConstraint(Component c)：返回指定组件的约束。
• layoutContainer(Container parent)：用于对指定容器进行布局。

下面的程序说明了 SpringLayout 类：

• 程序1：下面的程序将组件排列在一个JFrame中。我们创建了 1 个名为“ label ”的JLabel组件，并创建了一个名为“ textfield ”的JTextField ，并创建了 2 个类，一个是JFrame 类，另一个是SpringLayout 类，然后通过add()方法将它们添加到JFrame中。我们使用setvisible()方法设置框架的可见性。使用setLayout()方法设置布局。

  // Java program to show Example of SpringLayout.
  // in java. Importing different Package.
  import java.awt.Container;
  import javax.swing.JFrame;
  import javax.swing.JLabel;
  import javax.swing.JTextField;
  import javax.swing.SpringLayout;
    
  // construct a class springdemo
  public class Springdemo {
    
      // It is used to create and show GUI
      private static void createAndShowGUI()
      {
    
          // Creating Object of "JFrame" class
          JFrame frame = new JFrame("MySpringDemp");
    
          // Function to set default 
          // close operation of JFrame.
          frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    
          // to get content pane
          Container contentPane = frame.getContentPane();
    
          // Creating Object of "Springlayout" class
          SpringLayout layout = new SpringLayout();
    
          // to set content pane
          contentPane.setLayout(layout);
    
          // Initialization of object 
          // "label" of JLabel class.
          JLabel label = new JLabel("Label: ");
    
          // Initialization of object 
          // "label" of JLabel class.
          JTextField textField = new JTextField("Enter the text ", 15);
    
          // to add content pane of JLabel
          contentPane.add(label);
    
          // to add content pane of JTextField
          contentPane.add(textField);
    
          // It is used to put the layout
          // constraint in JFrame using springLayout class
          layout.putConstraint(SpringLayout.WEST, label, 
                     6, SpringLayout.WEST, contentPane);
                       
          layout.putConstraint(SpringLayout.NORTH, label, 
                     6, SpringLayout.NORTH, contentPane);
                       
          layout.putConstraint(SpringLayout.WEST, textField,
                               6, SpringLayout.EAST, label);
                                 
          layout.putConstraint(SpringLayout.NORTH, textField, 
                         6, SpringLayout.NORTH, contentPane);
                           
          layout.putConstraint(SpringLayout.EAST, contentPane, 
                             6, SpringLayout.EAST, textField);
                               
          layout.putConstraint(SpringLayout.SOUTH, contentPane, 
                             6, SpringLayout.SOUTH, textField);
    
          // Function to pack the JFrame.
          frame.pack();
    
          // Function to set visible status of JFrame.
          frame.setVisible(true);
      }
        
      // Main Method
      public static void main(String[] args)
      {
          javax.swing.SwingUtilities.invokeLater(new Runnable() 
          {
                
              // create a class
              public void run()
              {
                  // to create and show GUI
                  createAndShowGUI();
              }
          });
      }
  }
  

  输出：

• 程序 2：下面的程序将组件排列在一个JFrame中。我们创建了 1 个名为“ springlayout class”的类，并创建了一个名为“ b1”、“b2”、“b3”、“b4”、“b5 ”的 4 个JButton组件，然后通过add()方法将它们添加到JFrame中。我们使用setvisible()方法设置框架的可见性。布局由setLayout()方法设置。

  // Java program to show Example of SpringLayout.
  // in java. Importing different Package.
  import java.awt.*;
  import javax.swing.*;
    
  // construct a class Springclassdemo
  public class Springclassdemo {
        
      // Main Method
      public static void main(String[] arguments)
      {
    
          // main window
          // Function to set the default look 
          // and feel decorated status of JFrame.
          JFrame.setDefaultLookAndFeelDecorated(true);
    
          // Creating Object of "JFrame" class
          JFrame frame = new JFrame("SpringLayoutExample Example");
    
          // Function to set the default 
          // close operation status of JFrame
          frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    
          // Function to set the 
          // size status of JFrame
          frame.setSize(300, 200);
    
          // to get the content pane
          Container content = frame.getContentPane();
    
          // Creating Object of "SpringLayout" class
          SpringLayout layout = new SpringLayout();
    
          // to set the layout class
          frame.setLayout(layout);
    
          // Initialization of object 
          // "b1" of JButton class.
          Component b1 = new JButton("GEEKS");
    
          // Initialization of object 
          // "b2" of JButton class.
          Component b2 = new JButton("GFG");
    
          // Initialization of object
          // "b3" of JButton class.
          Component b3 = new JButton("JAVA");
    
          // Initialization of object
          // "b4" of JButton class.
          Component b4 = new JButton("Sudo Placement");
    
          // Adding the JButton "b1" on frame
          frame.add(b1);
    
          // Adding the JButton "b2" on frame
          frame.add(b2);
    
          // Adding the JButton "b3" on frame
          frame.add(b3);
    
          // Adding the JButton "b4" on frame
          frame.add(b4);
    
          // It is used to put the layout
          // constraint in JFrame using 
          // springLayout class on b1 JButton
          layout.putConstraint(SpringLayout.WEST, b1, 
                     25, SpringLayout.WEST, content);
                       
          layout.putConstraint(SpringLayout.NORTH, b1, 
                      10, SpringLayout.NORTH, content);
    
          // It is used to put the layout
          // constraint in JFrame using 
          // springLayout class on b2 JButton
          layout.putConstraint(SpringLayout.WEST, b2, 
                     50, SpringLayout.WEST, content);
                       
          layout.putConstraint(SpringLayout.NORTH, b2,
                          10, SpringLayout.SOUTH, b1);
    
          // It is used to put the layout
          // constraint in JFrame using 
          // springLayout class on b3 JButton
          layout.putConstraint(SpringLayout.WEST, b3, 
                     75, SpringLayout.WEST, content);
                       
          layout.putConstraint(SpringLayout.NORTH, b3, 
                          10, SpringLayout.SOUTH, b2);
    
          // It is used to put the layout
          // constraint in JFrame using 
          // springLayout class on b4 JButton
          layout.putConstraint(SpringLayout.WEST, b4, 
                          15, SpringLayout.EAST, b1);
                            
          layout.putConstraint(SpringLayout.NORTH, b4,
                      10, SpringLayout.NORTH, content);
    
          // Function to set the
          // visible status of JFrame
          frame.setVisible(true);
      }
  }
  

  输出：
  

注意：上述程序可能无法在在线 IDE 中运行。请使用离线编译器。

参考： https://docs.oracle.com/javase/7/docs/api/javax/swing/SpringLayout.html