GUI basic application

1.GUI summary
at present , The programs we write are all console based programs

GUI（Graphical User Interface） Graphical user interface , It can make the application look more friendly

2.Swing Concept
be located javax.swing

Swing Is pure java Components , Make applications have the same appearance and behavior in different platforms

3. What is a component , Containers ?
java The basic composition of the graphical user interface is components , Component is a graphic display on the screen , Objects that can interact with users

Components cannot be displayed separately , So it must be placed in a certain container (container) in , To show that

Containers can add multiple components , You can call the container's add() Method , Add different components to the container

4 Classification of components :
window (Frame) And panel (Panel) Called container component

Text input box (JTextField), Button (Button) Called functional components

5. Programming steps of graphical user interface :
When we create a graphical user interface, we first need to create a window , Usually use JFrame stay Swing Create a window in the program

You can add panels in the window , Usually use Jpanel Create a panel in the created window , Multiple panels can be created in one window

Different components can be added to the panel , You can also set the layout , We usually use nested method to realize layout

Create a demo of the window , And common methods :
import javax.swing.*;

public class JFrameDemo1 extends JFrame {

public JFrameDemo1(){

    this.setSize(500,300);   // Set the size of the window 
    this.setLocationRelativeTo(null);  // Set window center 
    this.setTitle(" Login screen ");   // Set the window title 
    this.setIconImage(new ImageIcon(" Wechat pictures _20211117191028.jpg").getImage());   // Set window icons , You need to copy the picture directly under the project , Can't put it in the bag 
    
}
public static void main(String[] args) {

   JFrame jFrame = new JFrameDemo1();   // Use JFrame Create a window object 
}

}

There are four layouts

The way :
FlowLayout
// Fluid layout , That is, a horizontal layout , Based on behavior , Arrange the components one by one , When a row is full , Automatically arrange to the next line
Flow layout example :

package javaGUI;

import javax.swing.;
import java.awt.;

public class JFrameDemo2_1 extends JFrame {

public JFrameDemo2_1(){

    this.setSize(500,300);
    this.setLocationRelativeTo(null);
    this.setTitle(" Login screen ");
    this.setIconImage(new ImageIcon(" Wechat pictures _20211117191028.jpg").getImage());
    this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    this.setResizable(false);

    JPanel jp = new JPanel();   // Use JPanel Create a panel 

    jp.setLayout(new FlowLayout(FlowLayout.LEFT));  // Create an anonymous flow layout object 
    JButton jButton1 = new JButton(" Button 1");   // Use JButton Create a button object 
    JButton jButton2 = new JButton(" Button 2");
    JButton jButton3 = new JButton(" Button 3");
    JButton jButton4 = new JButton(" Button 4");
    jp.add(jButton1);
    jp.add(jButton2);
    jp.add(jButton3);
    jp.add(jButton4);
    this.add(jp);
    this.setVisible(true);

}
public static void main(String[] args) {

   JFrame jFrame = new JFrameDemo2_1();
   
}

}

BorderLayout // Boundary layout , A way of layout with southeast, northwest and middle
Example of boundary layout :

package javaGUI;

import javax.swing.;
import javax.swing.border.Border;
import java.awt.;

public class JFrameDemo2_2 extends JFrame {

public JFrameDemo2_2(){

    this.setSize(500,300);
    this.setLocationRelativeTo(null);
    this.setTitle(" Login screen ");
    this.setIconImage(new ImageIcon(" Wechat pictures _20211117191028.jpg").getImage());
    this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    this.setResizable(false);

    JPanel jp = new JPanel();
    jp.setLayout(new BorderLayout());   // Use BorderLayout() Create an anonymous object with boundary layout 
    JButton jButton1 = new JButton(" Button 1");
    JButton jButton2 = new JButton(" Button 2");
    JButton jButton3 = new JButton(" Button 3");
    JButton jButton4 = new JButton(" Button 4");
    JButton jButton5 = new JButton(" Button 5");
    jp.add(jButton1, BorderLayout.NORTH);   // Set the position of each button separately 
    jp.add(jButton2, BorderLayout.EAST);
    jp.add(jButton3, BorderLayout.SOUTH);
    jp.add(jButton4, BorderLayout.WEST);
    jp.add(jButton5, BorderLayout.CENTER);

    this.add(jp);
    this.setVisible(true);
}
public static void main(String[] args) {

   JFrame jFrame = new JFrameDemo2_2();
}

}

GridLayout // Grid layout , A way of layout in grid form
Grid layout example :

package javaGUI;

import javax.swing.;
import java.awt.;

public class JFrameDemo2_3 extends JFrame {

public JFrameDemo2_3(){

    this.setSize(500,300);
    this.setLocationRelativeTo(null);
    this.setTitle(" Login screen ");
    this.setIconImage(new ImageIcon(" Wechat pictures _20211117191028.jpg").getImage());
    this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    this.setResizable(false);

    JPanel jp = new JPanel(new GridLayout(2,2));   // Use GridLayout(), How to create a grid layout , The number of rows and columns required is in brackets 
    JButton jButton1 = new JButton(" Button 1");
    JButton jButton2 = new JButton(" Button 2");
    JButton jButton3 = new JButton(" Button 3");
    JButton jButton4 = new JButton(" Button 4");
    jp.add(jButton1);
    jp.add(jButton2);
    jp.add(jButton3);
    jp.add(jButton4);
    this.add(jp);
    this.setVisible(true);
}
public static void main(String[] args) {

   JFrame jFrame = new JFrameDemo2_3();
}

}

setLayout(null); // Custom location , That is, define the location of the component by yourself
Custom layout example :

package javaGUI;

import javax.swing.;
import java.awt.;

public class JFrameDemo2_4 extends JFrame {

public JFrameDemo2_4(){

    this.setSize(500,300);
    this.setLocationRelativeTo(null);
    this.setTitle(" Login screen ");
    this.setIconImage(new ImageIcon(" Wechat pictures _20211117191028.jpg").getImage());
    this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    this.setResizable(false);
    this.setLayout(null);
    
    // Custom layout , You need to use the original window for layout 
    Container container = this.getContentPane();
    JButton jButton2 = new JButton(" Button 2");
    // Two sides and two lines are the way to create the original window 
    jButton2.setLocation(100,50);
    jButton2.setSize(80,50);
    container.add(jButton2);
    this.setVisible(true);
}
public static void main(String[] args) {

   JFrame jFrame = new JFrameDemo2_4();
}

}

Java GUI Introduction to common components

Be careful :

 After all components are created and set, you must use add() Method to the window , Otherwise, it will not show 

   jp.add(jButton4);   // Add the set button to the window 
    this.add(jp);

JLable( label ) // Used to display text or pictures
JPanel jp = new JPanel();

    jp.setLayout(new FlowLayout(FlowLayout.CENTER));
    JLabel accountLabel = new JLabel(" account number ");
           accountLabel.setFont(new Font(" Song style ",Font.BOLD,20));
          // accountLabel.setIcon(new ImageIcon(" Wechat pictures _20211117191028.jpg"));
    jp.add(accountLabel);

The renderings are as follows :

JtextField( The text box ) // Used to enter text
JTextField accountText = new JTextField(20);
jp.add(accountText);
The renderings are as follows :

JPasswordField( Password box ) // Used to enter the password
JLabel passwordLabel = new JLabel(“ password ”);
passwordLabel.setFont(new Font(“ Song style ”,Font.BOLD,20));
jp.add(passwordLabel);
JPasswordField jPasswordField = new JPasswordField(20);
jp.add(jPasswordField);
The renderings are as follows :

JTextArea( Multi-line text box ) / Used to input multiline text
JTextArea jTextArea = new JTextArea(5,20);
// Scroll panel , Scroll bars appear , Keep the size of the multiline text box unchanged
JScrollPane jScrollPane = new JScrollPane(jTextArea);
jp.add(jScrollPane);
The renderings are as follows :

JMenuBar( menu bar ) // Used to create a menu bar
JMenuBar jMenuBar = new JMenuBar();
JMenu( menu ) // Used to create a menu
JMenu jMenu1 = new JMenu(“ file ”);
JMenu jMenu2 = new JMenu(“ edit ”);
jMenuBar.add(jMenu1);
jMenuBar.add(jMenu2);
JMenuItem( A menu item ) // Used to create menu items
JMenuItem jMenuItem = new JMenuItem(“ newly build ”);
jMenu1.add(jMenuItem);

Java GUI Event handling

So far, what we have written is only a graphical user interface , There is no special function , In order to realize certain functions, event processing must be carried out
When users and GUI Components interact , Events will occur , such as : Press a button , Click the mouse, etc
One . Event handling ideas :
A source （ Event source ） Produce an event （ Event object ） And send it to the monitor , The listener simply waits , Until it receives an event , Once the event is accepted , The listener will handle these events

An event source must register a listener so that the listener can receive notifications about a particular event

Two . Common event handling methods :
Add event listeners for buttons
jButton1.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
String account = jButton1.getText();
String password = new String(jPasswordField.getPassword());
System.out.println(account);
System.out.println(password);
}
});
Add event monitoring for the mouse
// Add mouse event
jButton1.addMouseListener(new MouseAdapter() { //Adapter For adapter you , Use this method , You can choose the event type that needs to be rewritten , Instead of rewriting all the methods
@Override
public void mouseClicked(MouseEvent e) {
System.out.println(“ Mouse click ”);
}

        @Override
        public void mousePressed(MouseEvent e) {
            System.out.println(" The mouse click ");
        }

        @Override
        public void mouseReleased(MouseEvent e) {
            System.out.println(" Mouse release ");
        }

        @Override
        public void mouseEntered(MouseEvent e) {
            System.out.println(" Mouse migration ");
        }

        @Override
        public void mouseExited(MouseEvent e) {
            System.out.println(" Mouse removal ");
        }
    });

Add event monitoring for keyboard
// Add keyboard events
jTextField.addKeyListener(new KeyAdapter() {
@Override
public void keyTyped(KeyEvent e) {
System.out.println(“ Keyboard entry ”+e.getKeyCode());
}

        @Override
        public void keyPressed(KeyEvent e) {
            System.out.println(" Press the keyboard ");
        }

        @Override
        public void keyReleased(KeyEvent e) {
            System.out.println(" Keyboard release ");
        }
    });

Add event listening for the reset button
// Add event listening for the reset button
jButton2.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
jTextField.setText(“”);
jPasswordField.setText(“”);
}
})