GUI programming

I. Introduction

Core technology of GUI: AWT, Swing

Reasons for not being popular:

1. Because the interface is not beautiful

2. Need jre environment

Why should we study?

1. You can write some gadgets, plug-ins and so on you want
2. When working, you may also need to maintain the swing interface, which is very unlikely
3. Understand MVC architecture and monitoring

II. AWT

2.1 - AWT introduction

1. It contains many classes and interfaces! GUI: graphical user interface programming, Eclipse ➡ Java writing

2. Elements: window, button, text box

3. java.awt

   

2.2 - Components and containers

• Frame

  package com.gui;
  import java.awt.*;
  //The first interface of GUI
  public class GuiFrame {
      public static void main(String[] args) {
          //Frame, JDK, look at the source code
          Frame frame = new Frame("My first java Graphical interface window");
          //Set Visible 
          frame.setVisible(true);
          //Set window size
          frame.setSize(500,500);
          //Set background Color
          frame.setBackground(new Color(32,92,9));
          //Set initial position
          frame.setLocation(300,300);
          //Set fixed size
          frame.setResizable(false);
      }
  }
  

  

  • Problem: if the installation port cannot be closed, stop Java operation!
  • Review packaging:

  public class GuiFrame {
      public static void main(String[] args) {
          //Show multiple windows
          new MyFrame(100,100,200,200,Color.darkGray);
          new MyFrame(300,100,200,200,Color.blue);
          new MyFrame(100,300,200,200,Color.red);
          new MyFrame(300,300,200,200,Color.magenta);
      }
  }
  class MyFrame extends Frame{
      static int id = 0;//There may be multiple windows, we need a counter
      public MyFrame(int x,int y,int w,int h,Color color){
          super("MyFrame+ " + (++id));//Frame
          setVisible(true);  //Set Visible 
          setBounds(x,y,w,h);//Set window size and initial position
          setBackground(color);//Set background color
  
      }
  }
  

  

• Panel panel

  • Closed event resolved

  //The Panel can be regarded as a space, but it cannot exist alone and needs to be placed in the Frame
  public class GuiPanel {
      public static void main(String[] args) {
          Frame frame = new Frame();
          //Concept of layout
          Panel panel = new Panel();
          //Set layout
          frame.setLayout(null);
          //coordinate
          frame.setBounds(300,300,500,500);
          frame.setBackground(new Color(128, 173, 64));
          //Panel setting coordinates, relative to frame
          panel.setBounds(50,50,400,400);
          panel.setBackground(new Color(179, 65, 65));
          //panel join frame
          frame.add(panel);
          frame.setVisible(true);
          //Listen to the event. Listen to the window closing event system exit(0)
          /*
          Adapter mode
              23 A kind of design pattern
           */
          frame.addWindowListener(new WindowAdapter() {
              //What to do when clicking close
              @Override
              public void windowClosing(WindowEvent e) {
  //                super.windowClosing(e);
                  //End program
                  System.exit(0);
              }
          });
      }
  }
  

2.3 - Layout Manager

• Streaming layout

  public class GuiFlowLayout {
      public static void main(String[] args) {
          Frame frame = new Frame();
          //assembly ➡ Button
          Button button1 = new Button("button1");
          Button button2 = new Button("button2");
          Button button3 = new Button("button3");
          //Set as streaming layout
  //        frame.setLayout(new FlowLayout());  Center
          frame.setLayout(new FlowLayout(FlowLayout.LEFT));//Keep to the left
          frame.setSize(200,200);
          //Add the button
          frame.add(button1);
          frame.add(button2);
          frame.add(button3);
          //display
          frame.setVisible(true);
      }
  }
  

• East, West, North and South

  public class GuiBorderLayOut {
      public static void main(String[] args) {
          Frame frame = new Frame("BorderLayout");
          //Set button
          Button east = new Button("East");
          Button west = new Button("West");
          Button south = new Button("South");
          Button north = new Button("North");
          Button center = new Button("Center");
          //Join frame
          frame.add(east,BorderLayout.EAST);
          frame.add(west,BorderLayout.WEST);
          frame.add(south,BorderLayout.SOUTH);
          frame.add(north,BorderLayout.NORTH);
          frame.add(center,BorderLayout.CENTER);
          //Set frame
          frame.setSize(200,200);
          frame.setVisible(true);
      }
  }
  

• Table layout

  public class GuiGridLayout {
      public static void main(String[] args) {
          //Set btn
          Frame frame = new Frame();
          Button btn1 = new Button("btn1");
          Button btn2 = new Button("btn2");
          Button btn3 = new Button("btn3");
          Button btn4 = new Button("btn4");
          Button btn5 = new Button("btn5");
          Button btn6 = new Button("btn6");
          //Join frame
          frame.setLayout(new GridLayout(3,2));
          frame.add(btn1);
          frame.add(btn2);
          frame.add(btn3);
          frame.add(btn4);
          frame.add(btn5);
          frame.add(btn6);
          //frame settings
          frame.pack();//Java function! The function is to optimize the layout
          frame.setVisible(true);
      }
  }
  

• Interface practice (Frame + Panel + Button)

  

  public class GuiLayoutTest {
      public static void main(String[] args) {
          Frame frame = new Frame("Interface practice");
          frame.setSize(400,300);
          frame.setLocation(300,400);
          frame.setBackground(Color.GRAY);
          frame.setVisible(true);
          //Upper and lower parts (table layout upper and lower - two rows and one column)
          frame.setLayout(new GridLayout(2,1));
          //Four panels
          //above
          Panel p1 = new Panel(new BorderLayout());
          Panel p2 = new Panel(new GridLayout(2,1));
          p1.add(new Button("East1"),BorderLayout.EAST);
          p1.add(new Button("West1"),BorderLayout.WEST);
          p2.add(new Button("p2-btn-1"));
          p2.add(new Button("p2-btn-2"));
          p1.add(p2,BorderLayout.CENTER);
          frame.add(p1);
          //below
          Panel p3 = new Panel(new BorderLayout());
          Panel p4 = new Panel(new GridLayout(2,2));
          p3.add(new Button("East2"),BorderLayout.EAST);
          p3.add(new Button("West2"),BorderLayout.WEST);
          for (int i = 1; i <= 4; i++) {
              p4.add(new Button("p4-btn-"+i));
          }
          p3.add(p4);
          frame.add(p3);
          //lsnrctl stop 
          frame.addWindowListener(new WindowAdapter() {
              @Override
              public void windowClosing(WindowEvent e) {
                  System.exit(0);
              }
          });
      }
  }
  

2.4 - event monitoring

• Button monitoring

  public class GuiActionEvent {
      public static void main(String[] args) {
          //Press the button to start some events
          Frame frame = new Frame();
          Button button = new Button();
          //Because addActionListener() needs an ActionListener, we construct a MyActionListener implements ActionListener
          MyActionListener myActionListener = new MyActionListener();
          button.addActionListener(myActionListener);
          frame.add(button,BorderLayout.CENTER);
          frame.pack();
          frame.setVisible(true);
          windowClosing(frame);
      }
      //Turn off form event listening
      public static void windowClosing(Frame frame){
          frame.addWindowListener(new WindowAdapter() {
              @Override
              public void windowClosing(WindowEvent e) {
                  System.exit(0);
              }
          });
      }
  }
  //event listeners 
  class MyActionListener implements ActionListener{
      @Override
      public void actionPerformed(ActionEvent e) {
          System.out.println("AAA");
      }
  }
  

• Multiple buttons share a listening event

  public class GuiActionEvent {
      public static void main(String[] args) {
          /*
          Two buttons realize the same monitoring
          Start, stop
           */
          Frame frame = new Frame("start-stop it");
          Button startBtn = new Button("start");
          Button stopBtn = new Button("stop");
          /*
          The displayed definition will return the command. If the definition is not displayed, the default value will be taken
          You can write only one listening class for multiple buttons, which can be shared by listening classes.
           */
          startBtn.setActionCommand("startBtn-start");
          stopBtn.setActionCommand("stopBtn-stop");
  
          MyMonitor myMonitor = new MyMonitor();
          startBtn.addActionListener(myMonitor);
          stopBtn.addActionListener(myMonitor);
  
          frame.add(startBtn,BorderLayout.NORTH);
          frame.add(stopBtn,BorderLayout.SOUTH);
          frame.pack();
          frame.setVisible(true);
          windowClosing(frame);
  
      }
      //Turn off form event listening
      public static void windowClosing(Frame frame){
          frame.addWindowListener(new WindowAdapter() {
              @Override
              public void windowClosing(WindowEvent e) {
                  System.exit(0);
              }
          });
      }
  }
  //event listeners 
  class MyMonitor implements ActionListener{
      @Override
      public void actionPerformed(ActionEvent e) {
          //e.getActionCommand() gets the information of the button
          System.out.println("Button clicked: msg ➡ "+ e.getActionCommand());
          if(e.getActionCommand().equals("startBtn-start")){
              System.out.println("Start playing");//Depending on the return value of e.getActionCommand(), there will be different operations
          }
          if(e.getActionCommand().equals("stopBtn-stop")){
              System.out.println("stop playing");
          }
      }
  }
  

2.5 - input box TextField monitor

• Listen for text in text box

  public class GuiTextField {
      public static void main(String[] args) {
          //start-up
          new MyFrame();
      }
  }
  class MyFrame extends Frame{
      public MyFrame(){
          TextField textField = new TextField();
          add(textField);
          //Press Enter to trigger the text input in the listening text box
          textField.addActionListener(new MyActionListener());
          //Set code
          textField.setEchoChar('*');
          pack();
          setVisible(true);
      }
  }
  class MyActionListener implements ActionListener{
      @Override
      public void actionPerformed(ActionEvent e) {
          TextField field = (TextField) e.getSource();//Get some resources and return an object
          System.out.println(field.getText());//Gets the text of the input box
          field.setText("");//Press enter to clear. null is the object and "" is the string
      }
  }
  

2.6 - simple calculator, combination + internal class review

• oop principle, composition > inheritance

  class A extends B{
      //inherit
  }
  class A{
      public B b;//Combination to reduce coupling
  }
  

• Current calculator

  public class GuiCalc {
      public static void main(String[] args) {
          new Calculator();
      }
  }
  //Calculator class
  class Calculator extends Frame{
      public Calculator(){
          //3 text boxes
          TextField num1 = new TextField(10);
          TextField num2 = new TextField(10);
          TextField num3 = new TextField(20);
          //A label
          Label label = new Label("+");
          //A button
          Button button = new Button("=");
          button.addActionListener(new CalculatorListener(num1,num2,num3));
          //layout
          setLayout(new FlowLayout());
          add(num1);
          add(label);
          add(num2);
          add(button);
          add(num3);
          pack();
          setVisible(true);
      }
  }
  //Listener class
  class CalculatorListener implements ActionListener{
      //Get three variables
      private TextField num1,num2,num3;
      public CalculatorListener(TextField num1,TextField num2,TextField num3 ){
          this.num1 = num1;
          this.num2 = num2;
          this.num3 = num3;
      }
      @Override
      public void actionPerformed(ActionEvent e) {
          //1. Get num1 num2
          int n1 = Integer.parseInt(num1.getText());
          int n2 = Integer.parseInt(num2.getText());
          //2. Put this value into the third box after operation
          num3.setText(""+(n1+n2));
          //3. Clear the first two boxes
          num1.setText("");
          num2.setText("");
      }
  }
  

• The combination mode is completely transformed into oop

  public class GuiCalc {
      public static void main(String[] args) {
          new Calculator().loadFrame();
      }
  }
  //Calculator class
  class Calculator extends Frame{
      //attribute
      TextField num1,num2,num3;
      //method
      public void loadFrame(){
          //assembly
          num1 = new TextField(10);//Number of characters
          num2 = new TextField(10);
          num3 = new TextField(20);
          Label label = new Label("+");
          Button button = new Button("=");
          //monitor
          button.addActionListener(new CalculatorListener(this));
          //layout
          setLayout(new FlowLayout());
          add(num1);
          add(label);
          add(num2);
          add(button);
          add(num3);
          pack();
          setVisible(true);
      }
  }
  //Listener class
  class CalculatorListener implements ActionListener{
      //Get the calculator object and combine another class in one class
      Calculator calculator = null;
      public CalculatorListener(Calculator calculator){
          this.calculator = calculator;
      }
      @Override
      public void actionPerformed(ActionEvent e) {
          //1. Get num1 num2
          int n1 = Integer.parseInt(calculator.num1.getText());
          int n2 = Integer.parseInt(calculator.num2.getText());
          //2. Put this value into the third box after operation
          calculator.num3.setText(""+(n1+n2));
          //3. Clear the first two boxes
          calculator.num1.setText("");
          calculator.num2.setText("");
      }
  }
  

• Inner class

  • Better packaging

  public class GuiCalc {
      public static void main(String[] args) {
          Calculator calculator = new Calculator();
          calculator.loadFrame();
          closing(calculator);
      }
      public static void closing(Frame frame){
          frame.addWindowListener(new WindowAdapter() {
              @Override
              public void windowClosing(WindowEvent e) {
                  System.exit(0);
              }
          });
      }
  }
  //Calculator class
  class Calculator extends Frame{
      //attribute
      TextField num1,num2,num3;
      //method
      public void loadFrame(){
          //assembly
          num1 = new TextField(10);//Number of characters
          num2 = new TextField(10);
          num3 = new TextField(20);
          Label label = new Label("+");
          Button button = new Button("=");
          //monitor
          button.addActionListener(new CalculatorListener());
          //layout
          setLayout(new FlowLayout());
          add(num1);
          add(label);
          add(num2);
          add(button);
          add(num3);
          pack();
          setVisible(true);
      }
      //Listener class
      //The biggest advantage of internal classes is that they can access the properties and methods of external classes unimpeded!
      private class CalculatorListener implements ActionListener{
          @Override
          public void actionPerformed(ActionEvent e) {
              //1. Get num1 num2
              int n1 = Integer.parseInt(num1.getText());
              int n2 = Integer.parseInt(num2.getText());
              //2. Put this value into the third box after operation
              num3.setText(""+(n1+n2));
              //3. Clear the first two boxes
              num1.setText("");
              num2.setText("");
          }
      }
  }
  

2.7 - brush

• Simple operation

  public class GuiPaint {
      public static void main(String[] args) {
          new MyPaint().loadFrame();
      }
  }
  class MyPaint extends Frame{
      public void loadFrame(){
          setBounds(200,200,600,400);
          setVisible(true);
      }
      @Override
      public void paint(Graphics g) {
          //The brush needs to have color to draw
          g.setColor(Color.RED);
  //        g.drawOval(100,100,100,100);// Hollow circle ⚪
          g.fillOval(100,100,100,100);//disc 
          g.setColor(Color.GREEN);
          g.fillRect(150,200,200,200);//Solid rectangle
          //Make it a habit to use up the brush and restore it to its original color
      }
  }
  

2.8 - mouse monitoring

• Purpose: to achieve mouse painting!

  

  //Mouse monitoring events
  public class GuiMouseListener {
      public static void main(String[] args) {
          new MyPaintFrame("Draw a picture");
      }
  }
  //Own Frame
  class MyPaintFrame extends Frame{
      //You need a brush to draw, you need to monitor the current position of the mouse, and you need a collection to store this point
      ArrayList points;
      public MyPaintFrame(String title){
          super(title);
          setBounds(200,200,400,300);
          //Save mouse points
          points = new ArrayList<>();
          setVisible(true);
          //Mouse listener, facing this window
          this.addMouseListener(new MyMouseListener());
      }
      @Override
      public void paint(Graphics g) {
          //Draw and monitor mouse events
          Iterator iterator = points.iterator();
          while (iterator.hasNext()){
              Point point = (Point) iterator.next();
              g.setColor(Color.BLUE);
              g.fillOval(point.x,point.y,10,10);
          }
      }
      //Add a point to the interface
      public void addPaint(Point point){
          points.add(point);
      }
      //Adapter mode
      private class MyMouseListener extends MouseAdapter {
          //Mouse: Press, pop up, hold down
          @Override//Press
          public void mousePressed(MouseEvent e) {
              MyPaintFrame myPaintFrame = (MyPaintFrame) e.getSource();
              //When you click here, a point will be generated in the interface!
              //This point is the point of the mouse
              myPaintFrame.addPaint(new Point(e.getX(),e.getY()));
  
              //You need to redraw every time you click the mouse
              myPaintFrame.repaint();//Refresh
          }
      }
  }
  

2.9 - window monitoring

• The most commonly used windows are closing and activating

  public class GuiWindowListener {
      public static void main(String[] args) {
          new WindowFrame();
      }
  }
  class WindowFrame extends Frame{
      public WindowFrame(){
          setBackground(Color.BLUE);
          setBounds(100,100,200,200);
          setVisible(true);
          this.addWindowListener(new WindowAdapter() {
              //close window
              @Override
              public void windowClosing(WindowEvent e) {
                  System.out.println("windowClosing");
                  System.exit(0);
              }
              //activation
              @Override
              public void windowActivated(WindowEvent e) {
                  WindowFrame source = (WindowFrame) e.getSource();
                  source.setTitle("Activated");
                  System.out.println("windowActivated");
              }
          });
      }
  }
  

2.10 - keyboard monitoring

• Different results will be produced according to different operations

  public class GuiKeyListener {
      public static void main(String[] args) {
          new KeyFrame();
      }
  }
  class KeyFrame extends Frame{
      public KeyFrame(){
          setBounds(100,200,300,400);
          setVisible(true);
          this.addKeyListener(new KeyAdapter() {
              @Override
              public void keyPressed(KeyEvent e) {
                  //Which key is the current key
                  int keyCode = e.getKeyCode();//You do not need to record this hexadecimal value, but use the static attribute VK directly_ xxx
                  System.out.println(keyCode);
                  if(keyCode == KeyEvent.VK_UP){
                      System.out.println("You pressed the up button!");
                  }
              }
          });
      }
  }
  

Three Swing

3.1 - Windows, panels

• The first case (JFrame, JLabel)

  public class JFrameDemo {
      public static void main(String[] args) {
          //Create a window
          new MyJFrame().init();
      }
  }
  class MyJFrame extends JFrame{
      public void init(){
          this.setBounds(10,10,200,300);
          this.setVisible(true);
          JLabel label = new JLabel("Welcome to java world");
          this.add(label);
          //Center the text label and set the horizontal alignment
          label.setHorizontalAlignment(SwingConstants.CENTER);
          //Get a container
          Container container = this.getContentPane();
          container.setBackground(Color.CYAN);
      }
  }
  

3.2 - pop up window

• JDialog, binding JButton event

  //main window
  public class DialogDemo extends JFrame {
      public static void main(String[] args) {
          new DialogDemo();
      }
      public DialogDemo() {
          this.setVisible(true);
          this.setSize(700,500);
          this.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
          //Put things in JFrame ➡  container
          Container container = this.getContentPane();
          //Absolute layout
          container.setLayout(null);
          //Button
          JButton button = new JButton("Click to pop up a dialog box");//establish
          button.setBounds(30,30,200,50);
          container.add(button);
          //When you click the button, a pop-up window pops up
          button.addActionListener(new ActionListener() {//monitor
              @Override
              public void actionPerformed(ActionEvent e) {
                  //Spring frame
                  new MyDialog();
              }
          });
      }
  }
  //Pop up window
  class MyDialog extends JDialog{
      public MyDialog(){
          this.setVisible(true);
          this.setBounds(100,100,500,500);
          Container container = this.getContentPane();
          container.setLayout(null);
          container.add(new Label("Welcome to the Java world"));
      }
  }
  

3.3 - Labels

• Label

  new JLabel("xxx");
  

• Icon icon

  //Icon, need to implement class, Frame inheritance
  public class IconDemo extends JFrame implements Icon {
      private int width;
      private int height;
      /*
      Structure without / with parameters
       */
      public IconDemo(){}
      public IconDemo(int width,int height){
          this.width = width;
          this.height = height;
      }
      public void init(){
          IconDemo icon = new IconDemo(15, 15);
          //Icons can be placed on labels or buttons!
          JLabel label = new JLabel("icon test", icon, SwingConstants.CENTER);
          Container container = getContentPane();
          container.add(label);
          this.setVisible(true);
          this.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
  
      }
      public static void main(String[] args) {
          new IconDemo().init();
      }
      @Override
      public void paintIcon(Component c, Graphics g, int x, int y) {
          g.fillOval(x,y,width,height);
      }
      @Override
      public int getIconWidth() {
          return this.width;
      }
      @Override
      public int getIconHeight() {
          return this.height;
      }
  }
  

• Picture Icon (logo)

  //Picture (logo)
  public class ImageIconDemo extends JFrame {
      public ImageIconDemo() {
          JLabel label = new JLabel("ImageIcon");
          //Get the address of the picture
          URL url = ImageIconDemo.class.getResource("tree.png");
          ImageIcon imageIcon = new ImageIcon(url);//Do not conflict in naming
          label.setIcon(imageIcon);
          label.setHorizontalAlignment(SwingConstants.CENTER);
          Container container = getContentPane();
          container.add(label);
          setVisible(true);
          setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
          setBounds(100,200,400,400);
      }
      public static void main(String[] args) {
          new ImageIconDemo();
      }
  }
  

3.4 - panel

• JPanel

  public class JPanelDemo extends JFrame {
      public static void main(String[] args) {
          new JPanelDemo();
      }
      public JPanelDemo() {
          Container container = this.getContentPane();
          container.setLayout(new GridLayout(2,1,10,10));//The following parameters mean spacing
          JPanel panel1 = new JPanel(new GridLayout(1, 3));
          JPanel panel2 = new JPanel(new GridLayout(1, 2));
          JPanel panel3 = new JPanel(new GridLayout(2, 1));
          JPanel panel4 = new JPanel(new GridLayout(3, 2));
          panel1.add(new JButton("1"));
          panel1.add(new JButton("1"));
          panel1.add(new JButton("1"));
          panel2.add(new JButton("2"));
          panel2.add(new JButton("2"));
          panel3.add(new JButton("3"));
          panel3.add(new JButton("3"));
          panel4.add(new JButton("4"));
          panel4.add(new JButton("4"));
          panel4.add(new JButton("4"));
          panel4.add(new JButton("4"));
          panel4.add(new JButton("4"));
          panel4.add(new JButton("4"));
          container.add(panel1);
          container.add(panel2);
          container.add(panel3);
          container.add(panel4);
          this.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
          this.setVisible(true);
          this.setSize(500,500);
      }
  }
  

• JscrollPanel

  public class JScrollDemo extends JFrame {
      public JScrollDemo(){
          Container container = this.getContentPane();
          //Text field
          JTextArea textArea = new JTextArea(20,50);
          textArea.setText("Welcome to study Java");
          //Scroll panel
          JScrollPane scrollPane = new JScrollPane(textArea);
          container.add(scrollPane);
          this.setVisible(true);
          this.setBounds(100,100,300,350);
          this.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
      }
      public static void main(String[] args) {
          new JScrollDemo();
      }
  }
  

3.5 - buttons

• Picture button

  public class JButtonDemo extends JFrame {
      public JButtonDemo(){
          Container container = this.getContentPane();
          //Program picture Icon
          URL resource = JButtonDemo.class.getResource("tree.png");
          Icon icon = new ImageIcon(resource);
          //Put the icon on the button
          JButton button = new JButton();
          button.setIcon(icon);
          button.setToolTipText("Button picture!");
          //Add container
          container.add(button);
  
          this.setVisible(true);
          this.setSize(500,300);
          this.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
      }
      public static void main(String[] args) {
          new JButtonDemo();
      }
  }
  

• Radio box, round

  public class JButtonDemo extends JFrame {
      public JButtonDemo(){
          Container container = this.getContentPane();
          //Program picture Icon
          URL resource = JButtonDemo.class.getResource("tree.png");
          Icon icon = new ImageIcon(resource);
          //Radio 
          JRadioButton radioButton01 = new JRadioButton("JRadioButton01");
          JRadioButton radioButton02 = new JRadioButton("JRadioButton02");
          JRadioButton radioButton03 = new JRadioButton("JRadioButton03");
          //Since only one radio box can be selected, it is generally divided into one group.
          ButtonGroup group = new ButtonGroup();
          group.add(radioButton01);
          group.add(radioButton02);
          group.add(radioButton03);
          //Upper, middle and lower
          container.add(radioButton01,BorderLayout.CENTER);
          container.add(radioButton02,BorderLayout.SOUTH);
          container.add(radioButton03,BorderLayout.NORTH);
          this.setVisible(true);
          this.setSize(500,300);
          this.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
      }
      public static void main(String[] args) {
          new JButtonDemo();
      }
  }
  

• Multiple selection box, box

  public class JButtonDemo extends JFrame {
      public JButtonDemo(){
          Container container = this.getContentPane();
          //Program picture Icon
          URL resource = JButtonDemo.class.getResource("tree.png");
          Icon icon = new ImageIcon(resource);
          //Radio 
          JCheckBox checkBox01 = new JCheckBox("checkBox01");
          JCheckBox checkBox02 = new JCheckBox("checkBox02");
          JCheckBox checkBox03 = new JCheckBox("checkBox03");
          //Multiple selections do not need grouping
          //Upper, middle and lower
          container.add(checkBox01,BorderLayout.CENTER);
          container.add(checkBox02,BorderLayout.SOUTH);
          container.add(checkBox03,BorderLayout.NORTH);
          this.setVisible(true);
          this.setSize(500,300);
          this.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
      }
      public static void main(String[] args) {
          new JButtonDemo();
      }
  }
  

3.6 - List

• Drop down box

  public class ComboboxDemo extends JFrame {
      public ComboboxDemo(){
          Container container = this.getContentPane();
          JComboBox status = new JComboBox();
          status.addItem(null);
          status.addItem("It's showing");
          status.addItem("Removed from the shelf");
          status.addItem("Coming soon");
          container.add(status);
          this.setVisible(true);
          this.setSize(500,300);
          this.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
      }
      public static void main(String[] args) {
          new ComboboxDemo();
      }
  }
  

• list box

  public class ComboboxDemo extends JFrame {
      public ComboboxDemo(){
          Container container = this.getContentPane();
          //Generate the contents of the list
  //        String[] contents = {"1","2","3"};
          Vector contents = new Vector();
          contents.add("Zhang San");
          contents.add("Li Si");
          contents.add("Wang Wu");
          //The list needs to be filled
          JList list = new JList(contents);
          container.add(list);
          this.setVisible(true);
          this.setSize(500,300);
          this.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
      }
      public static void main(String[] args) {
          new ComboboxDemo();
      }
  }
  

• Application scenario

  • Drop down to select region or some individual options
  • List, display information, usually dynamic capacity expansion

3.7 - text box

• Text box

  public class TextDemo extends JFrame {
      public TextDemo(){
          Container container = this.getContentPane();
          JTextField field01 = new JTextField("hello");
          JTextField field02 = new JTextField("world",20);
          container.add(field01,BorderLayout.NORTH);
          container.add(field02,BorderLayout.SOUTH);
          this.setVisible(true);
          this.setSize(500,300);
          this.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
      }
      public static void main(String[] args) {
          new TextDemo();
      }
  }
  

• Password box

  public class TextDemo extends JFrame {
      public TextDemo(){
          Container container = this.getContentPane();
          //panel
          JPasswordField field = new JPasswordField();//****
          field.setEchoChar('*');
          container.add(field);
          this.setVisible(true);
          this.setSize(500,300);
          this.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
      }
      public static void main(String[] args) {
          new TextDemo();
      }
  }
  

• Text field

  public class JScrollDemo extends JFrame {
      public JScrollDemo(){
          Container container = this.getContentPane();
          //Text field
          JTextArea textArea = new JTextArea(20,50);
          textArea.setText("Welcome to study Java");
          //Scroll panel
          JScrollPane scrollPane = new JScrollPane(textArea);
          container.add(scrollPane);
          this.setVisible(true);
          this.setBounds(100,100,300,350);
          this.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
      }
      public static void main(String[] args) {
          new JScrollDemo();
      }
  }
  

Greedy snake

• Frame, if the time slice is small enough, it is animation. 30 frames a second, 60 frames pass through the human eye, which is similar to 30 frames. Connect is animation, open is static picture!

• Keyboard monitor

• Timer timer

  //Data center
  public class Data {
      private static URL headerURL = Data.class.getResource("statics/header.png");
      public static ImageIcon header = new ImageIcon(headerURL);
      private static URL upURL = Data.class.getResource("statics/up.png");
      private static URL downURL = Data.class.getResource("statics/down.png");
      private static URL leftURL = Data.class.getResource("statics/left.png");
      private static URL rightURL = Data.class.getResource("statics/right.png");
      public static ImageIcon up = new ImageIcon(upURL);
      public static ImageIcon down = new ImageIcon(downURL);
      public static ImageIcon left = new ImageIcon(leftURL);
      public static ImageIcon right = new ImageIcon(rightURL);
      private static URL bodyURL = Data.class.getResource("statics/body.png");
      public static ImageIcon body = new ImageIcon(bodyURL);
      private static URL foodURL = Data.class.getResource("statics/food.png");
      public static ImageIcon food = new ImageIcon(foodURL);
  }
  //Main startup class of the game
  public class GameStart {
      public static void main(String[] args) {
          JFrame frame = new JFrame();
          frame.setBounds(10,10,900,720);
          frame.setResizable(false);//Window size is immutable
          frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
          //The normal game interface should be on the panel!
          frame.add(new GamePanel());
          frame.setVisible(true);
      }
  }
  //Game panel ➡ Main operation
  public class GamePanel extends JPanel implements KeyListener , ActionListener {
      //Define the data structure of the snake
      int length;//Snake length
      int[] snakeX = new int[600];//X coordinate of snake 25 * 30
      int[] snakeY = new int[500];//Y coordinate of snake 25 * 25
      String direction;//Initial direction
      //Failed
      boolean isFail = false; //Failure status
      //Coordinates of food
      int foodX;
      int foodY;
      Random random = new Random();
      //Current state of the game: start / stop
      boolean isStart = false; //Default stop
      //Timer in milliseconds 1000ms = 1s
      Timer timer = new Timer(100,this);//Execute once every 100 milliseconds
      //integral
      int score;
      public GamePanel(){
          init();
          //Get focus and keyboard events
          this.setFocusable(true);//Get focus event
          this.addKeyListener(this);//Get keyboard listening events
          timer.start();//The game starts at the beginning
          score = 0;
      }
      //Initialization method
      public void init(){
          length = 3;
          snakeX[0] = 100; snakeY[0] = 100; //Head coordinates
          snakeX[1] = 75; snakeY[1] = 100; //Coordinates of the first body
          snakeX[2] = 50; snakeY[2] = 100; //Coordinates of the second body
          direction = "R"; //Initial direction right
          //Randomly distribute the food on the interface
          foodX = 25 + 25*random.nextInt(34);
          foodY = 75 + 25*random.nextInt(24);
      }
      //Drawing panel, everything in our game, uses this brush
      @Override
      protected void paintComponent(Graphics g) {
          super.paintComponent(g);//Clear screen
          this.setBackground(Color.WHITE);//Background white, default
          //Draw static panel
          Data.header.paintIcon(this,g,25,11);//Draw the ad on the head
          g.fillRect(25,75,850,600);//Default game interface
          //Draw integral
          g.setColor(Color.WHITE);
          g.setFont(new Font("Microsoft YaHei ",Font.BOLD,18));//Set font
          g.drawString("length "+length,750,35);
          g.drawString("fraction "+score,750,50);
          //Draw food
          Data.food.paintIcon(this,g,foodX,foodY);
          //Draw the little snake
          if(direction.equals("R")){
              Data.right.paintIcon(this,g,snakeX[0],snakeY[0]); //The snakehead is initialized to the right and judged by the direction
          }else if(direction.equals("L")){
              Data.left.paintIcon(this,g,snakeX[0],snakeY[0]); //The snakehead is initialized to the right and judged by the direction
          }else if(direction.equals("U")){
              Data.up.paintIcon(this,g,snakeX[0],snakeY[0]); //The snakehead is initialized to the right and judged by the direction
          }else if(direction.equals("D")){
              Data.down.paintIcon(this,g,snakeX[0],snakeY[0]); //The snakehead is initialized to the right and judged by the direction
          }
          for (int i = 1; i < length; i++) {
              Data.body.paintIcon(this,g,snakeX[i],snakeY[i]); //Initialize the first body
          }
          //Game status
          if(isStart==false) {
              g.setColor(Color.WHITE);
              g.setFont(new Font("Microsoft YaHei ", Font.BOLD, 40));//Set font
              g.drawString("Press the space bar to start the game", 300, 300);
          }
          //Failure status
          if(isFail){
              g.setColor(Color.RED);
              g.setFont(new Font("Microsoft YaHei ",Font.BOLD,40));//Set font
              g.drawString("The game failed. Press the space to start again",300,300);
          }
      }
      //Keyboard listening events
      @Override
      public void keyPressed(KeyEvent e) {
          int keyCode = e.getKeyCode();//When getting keyboard keys
          if(keyCode == KeyEvent.VK_SPACE){//Space
              if(isFail){
                  //restart
                  isFail = false;
                  init();
              }else{
                  isStart = !isStart;//Reverse
              }
              repaint();
          }
          //Snake Movement
          if(keyCode == KeyEvent.VK_UP){
              direction = "U";
          }else if(keyCode == KeyEvent.VK_DOWN){
              direction = "D";
          }else if(keyCode == KeyEvent.VK_LEFT){
              direction = "L";
          }else if(keyCode == KeyEvent.VK_RIGHT){
              direction = "R";
          }
      }
      //Event listening ➡  Refresh through fixed events, 1s = 10 times
      @Override
      public void actionPerformed(ActionEvent e) {
          if(isStart && !isFail){//If the game starts, let the snake move
              //Eat food
              if(snakeX[0] == foodX && snakeY[0] == foodY){
                  length++;//Length + 1
                  score = score + 10;//Points + 10
                  //Random distribution of food again
                  foodX = 25 + 25*random.nextInt(34);
                  foodY = 75 + 25*random.nextInt(24);
              }
              //move
              for (int i = length - 1; i > 0; i--) {//The next section moves the position of the previous section
                  snakeX[i] = snakeX[i-1];
                  snakeY[i] = snakeY[i-1];
              }
              if(direction.equals("R")){
                  snakeX[0] = snakeX[0]+25;
                  if(snakeX[0] > 850){snakeX[0] = 25;}
              }else if(direction.equals("L")){
                  snakeX[0] = snakeX[0]-25;
                  if(snakeX[0] < 25){snakeX[0] = 850;}
              }else if(direction.equals("U")){
                  snakeY[0] = snakeY[0]-25;
                  if(snakeY[0] < 75){snakeY[0] = 650;}
              }else if(direction.equals("D")){
                  snakeY[0] = snakeY[0]+25;
                  if(snakeY[0] > 650 ){snakeY[0] = 75;}
              }
              //Failure judgment, bumping into yourself is failure
              for (int i = 1; i < length; i++) {
                  if(snakeX[0]==snakeX[i] && snakeY[0]==snakeY[i]){
                      isFail = true;
                  }
              }
              repaint();//Redraw page
          }
          timer.start();//Timer on
      }
      @Override
      public void keyReleased(KeyEvent e) { }
      @Override
      public void keyTyped(KeyEvent e) { }
  }
  

• Required accessories