Experiment 5: Gui

• The experiment purpose

Design related classes through graphical interfaces 、 Interfaces, etc. , Realize the development of user graphical application ; Further consolidate JDBC Connect to the database and read and write files .

• The goal of the experiment

1. Be able to master common GUI How to use the control components , adopt java.awt Packages and Javax.swing The classes and interfaces in the package realize the development of user graphical interface ;
2. Be able to use Java Event handling mechanism of , adopt JDBC Operating the database , Realize user login function ;
3. Be able to master and use I/O Stream operates on files .

• Experimental content

1 Experimental environment

java version "13.0.2" 2020-01-14

Java(TM) SE Runtime Environment (build 13.0.2+8)

Java HotSpot(TM) 64-Bit Server VM (build 13.0.2+8, mixed mode, sharing)

2 The specific content of the experiment

1. utilize GUI Design and implement a calculator program （ notes ： At least four basic operations of addition, subtraction, multiplication and division should be realized ）.
2. Design a graphic application about file operation , At least realize the following functions ：

 a) Contains a text box and add button , After entering text in the text box , Click the Add button to write the text in the text box in the file ;

  b) Contains a read button , After clicking this button , Can read file contents , And display it in the text box .

• Analysis of experimental process

1 The experimental steps

1. Calculator program , Create a window page , At the same time, add several methods of requirements to this window , To realize the methods of addition, subtraction, multiplication and division .

   The code is as follows ：

package demo;

import javax.swing.*;

import java.awt.*;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;



public class MyJfram extends JFrame implements ActionListener {

    private final JPanel upBottom = new JPanel();// Upper component 

    private final Button clearButton = new Button("clear");

    private JTextField show = new JFormattedTextField();

    private final JPanel downBottom = new JPanel();// Next set up 

    private final String string1 = "0123456789.";

    private final String string2 = "[\\+\\-*/]{1}";



    public void inti() {

        this.setBounds(500, 200, 300, 300);

        this.setTitle(" Computing machine ");

        this.setVisible(true);

        this.setDefaultCloseOperation(EXIT_ON_CLOSE);

        this.setResizable(false);

        this.upBottom();

        this.downBottom();

    }



    public void upBottom() {

        this.upBottom.setLayout(new FlowLayout());// Fluid layout 

        this.show.setPreferredSize(new Dimension(220, 30));// Set the size method in the component 

        this.upBottom.add(show);

        this.upBottom.add(clearButton);

        this.upBottom.setForeground(Color.RED);

        this.add(upBottom, BorderLayout.NORTH);

        clearButton.addActionListener(this);// Global monitoring 

    }



    public void downBottom() {

        String s = new String("123+456-789/0.*=");

        this.downBottom.setLayout(new GridLayout(4, 4));// Grid layout 

        for (int i = 0; i < 16; i++) {

            Button button = new Button();

            button.setLabel(String.valueOf(s.charAt(i)));

            button.addActionListener(this);

            downBottom.add(button);

        }

        this.add(downBottom, BorderLayout.CENTER);

    }



    public static void main(String[] args) {

        MyJfram myJfram = new MyJfram();

        myJfram.inti();

    }



    String firstNum = null;//

    String operate = null;

    String secondNum = null;



    @Override

    public void actionPerformed(ActionEvent e) {

        String command = e.getActionCommand();

        if (string1.contains(command)) {

            this.show.setText(this.show.getText() + command);

            this.show.setHorizontalAlignment(JTextField.RIGHT);

        } else if (command.matches(string2)) {

            operate = command;

            firstNum = this.show.getText();

            this.show.setText("");

        } else if ("=".equals(command)) {

            secondNum = this.show.getText();

            Double a = Double.valueOf(firstNum);

            Double b = Double.valueOf(secondNum);

            Double result = null;

            switch (operate) {

                case "+":

                    result = a + b;

                    break;

                case "-":

                    result = a - b;

                    break;

                case "*":

                    result = a * b;

                    break;

                case "/":

                    if (b != 0) {

                        result = a / b;

                    } else {

                        JOptionPane.showMessageDialog(this, " The dividend cannot be zero 0");

                    }

                    break;

                default:

                    break;

            }

            assert result != null;

            this.show.setText(result.toString());

        } else if ("clear".equals(command)) {

            this.show.setText("");

            firstNum = null;

            secondNum = null;

        }

    }

}

Calculation 12*5=60

1. Graphical applications , Create a window interface , Add two components to this window , A window for input to the system , A window is used to output to the system .

   The code is as follows ：

package demo;

import javax.swing.*;

import java.awt.*;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import java.io.*;



public class MyJfram extends JFrame implements ActionListener {

    public TextArea textArea = new TextArea();

    public Button button = new Button();

    public Button button1 = new Button();

    public StringBuffer inputString = new StringBuffer();



    public void inti() {

        this.setBounds(500, 200, 300, 300);

        this.setVisible(true);

        this.setResizable(false);

        this.setTitle(" Input and output ");

        this.setDefaultCloseOperation(EXIT_ON_CLOSE);

        this.setLayout(new FlowLayout());

        up();

        down();

    }



    private void down() {

        button.setLabel("InputText");

        button.setPreferredSize(new Dimension(300, 60));

        button.addActionListener(this);

        this.add(button, BorderLayout.SOUTH);

        button1.setLabel("OutText");

        button1.setPreferredSize(new Dimension(300, 60));

        button1.addActionListener(this);

        this.add(button1, BorderLayout.SOUTH);

    }



    public void up() {

        textArea.setPreferredSize(new Dimension(270, 100));

        textArea.setFont(new Font(" Song style ", Font.BOLD, 20));

        this.add(textArea);

    }



    public static void main(String[] args) {

        MyJfram myJfram = new MyJfram();

        myJfram.inti();

    }



    String string = "InputText";



    @Override

    public void actionPerformed(ActionEvent e) {

        String command = e.getActionCommand();

        if (string.equals(command)) {

            String text = textArea.getText();

            writerText(text);

        } else {

            readText();

        }

    }



    private void readText() {

        File file = new File("D:\\VM\\a.txt");

        try (FileReader fileReader = new FileReader(file)) {

            BufferedReader bufferedReader = new BufferedReader(fileReader);

            String len = null;

            StringBuilder result = new StringBuilder();

            while ((len = bufferedReader.readLine()) != null) {

                result.append(len);

            }

            JOptionPane.showMessageDialog(this, " Read successful ");

            textArea.setText(result.toString());

        } catch (IOException e) {

            e.printStackTrace();

        }

    }



    private void writerText(String text) {

        File file = new File("D:\\VM\\a.txt");

        try (FileWriter fileWriter = new FileWriter(file)) {

            inputString.append(text);

            fileWriter.write(inputString.toString());

            textArea.setText("");

            JOptionPane.showMessageDialog(this, " Archive success ");

        } catch (IOException e) {

            e.printStackTrace();

        }

    }

}

initialization ：

Then the output ：

4.2 error analysis

1. In this experiment , It must be considered that the data during calculation cannot exceed the range , Otherwise, data loss will occur , Also consider that the divisor cannot be 0.

2. When inputting and outputting files , If you do not consider the closure of the file stream, the file data may be garbled , You have to set it up Java structure , Set the character type to UTF8.

• Summary of the experiment

answer ：Java The basic component of GUI is component , A component is an object that is displayed graphically on the screen and can interact with users. Components cannot be displayed independently , The components must be placed in a container (container) Can be displayed in . Containers can hold multiple components , By calling the add(Component comp) Method to add a component to the container . Graphical user interface (GUI) is an interface display format for communication between people and computers , Allows users to manipulate icons or menu options on the screen using input devices such as a mouse , To select the command 、 Call file 、 Start a program or perform other routine tasks . Compared to a character interface that uses keyboard input text or character commands to perform routine tasks , GUI has many advantages . The GUI consists of windows 、 The drop-down menu 、 Dialog box and its corresponding control mechanism constitute , It's standardized in all kinds of new applications , That is, the same operation is always done in the same way , In the graphical user interface , What users see and operate are graphic objects , The application is the technology of computer graphics .