作者：叄念

1.如何建立GUI（由小元件進行演示講解）

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;

public class Demo01 {
    public static void main(String[] args) {
        // 1.建立jFrame
        JFrame jFrame = new JFrame();
        /** 下面這一行程式碼的效果是：在使用者關閉視窗是把程式結束掉 */
 

        jFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        // 2.建立一個元件（widget）—— 按鈕
        JButton jButton = new JButton("按鈕名稱");
        // 3.將元件（按鈕）新增到到jFrame(裡面的Pane)上
        jFrame.getContentPane().add(jButton);
        // 4.設定尺寸並 顯示
        jFrame.setSize(300, 300);
        jFrame.setVisible(true
 
);
    }
}

執行後效果展示 ：

2.實現監聽事件

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;

public class Demo02 implements ActionListener {// 1.實現時間監聽 需要實現該介面（事件只會通知所有實現ActionListener介面的類）
    JButton jButton;

    public static
 
 void main(String[] args) {
        Demo02 gui = new Demo02();
        gui.go();
    }

    public void go() {
        JFrame jFrame = new JFrame();
        jButton = new JButton("按鈕名稱");
        // 3.為按鈕進行註冊
        jButton.addActionListener(this);

        jFrame.getContentPane().add(jButton);
        jFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        jFrame.setSize(300, 300);
        jFrame.setVisible(true);
    }

    // 2.實現介面後需要重寫該方法（你希望要執行的事件）
    @Override
    public void actionPerformed(ActionEvent e) {
        //4.按鈕需要做的操作
        jButton.setText("事件監聽，有使用者點選");
    }
}

點選後效果展示 ：

2.GUI簡單圖形繪製案例

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.GradientPaint;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class Demo03{
    public static void main(String[] args) {
        JFrame jFrame = new JFrame();
        /**繪製一個2D圖形(圓形)*/
//      jFrame.add(new JPanel() {
//          @Override
//          protected void paintComponent(Graphics g) {
//              g.setColor(Color.red);
//              g.fillOval(70, 70, 100, 100);
//          }
//      });

        /**繪製一個漸變色圓,拖動視窗可變色*/
        jFrame.add(new JPanel() {
            @Override
            protected void paintComponent(Graphics g) {
                Graphics2D g2d = (Graphics2D) g;

                //1.獲取隨機RGB三個引數，並製作顏色
                int red  = (int)(Math.random()*255);
                int green  = (int)(Math.random()*255);
                int blue  = (int)(Math.random()*255);
                Color startColor = new Color(red, green, blue);

                //2.再次獲取隨機RGB三個引數，並製作顏色
                red  = (int)(Math.random()*255);
                green  = (int)(Math.random()*255);
                blue  = (int)(Math.random()*255);
                Color endColor = new Color(red, green, blue);

                //3.製作漸變色
                GradientPaint gradientPaint = new GradientPaint(70, 70, startColor, 150,150,endColor);
                g2d.setPaint(gradientPaint);
                //4.畫圓
                g2d.fillOval(70, 70, 100, 100);
            }
        });

        jFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        jFrame.setSize(300, 300);
        jFrame.setVisible(true);
    }


}

效果展示 ：

3.GUI的佈局

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.GradientPaint;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;

public class Demo04 {
    JFrame jFrame;
    JLabel jLabel;

    public static void main(String[] args) {
        Demo04 event = new Demo04();
        event.go();
    }

    public void go() {
        jFrame = new JFrame();

        //1.建立若干元件
        JButton colorButton = new JButton("改變顏色");
        JButton lableButton = new JButton("改變lable文字");
        jLabel = new JLabel("這是一個JLabel");

        //2.為Button元件進行監聽註冊
        colorButton.addActionListener(new ColorListenner());
        lableButton.addActionListener(new LabelListenner());

        //3.將元件新增到jFrame上，並佈局顯示
        jFrame.add(BorderLayout.WEST,jLabel);
        jFrame.add(BorderLayout.EAST,lableButton);
        jFrame.add(BorderLayout.SOUTH, colorButton);
        jFrame.add(BorderLayout.CENTER, new JPanel() {
            @Override
            protected void paintComponent(Graphics g) {
                Graphics2D g2d = (Graphics2D) g;

                int red = (int) (Math.random() * 255);
                int green = (int) (Math.random() * 255);
                int blue = (int) (Math.random() * 255);
                Color startColor = new Color(red, green, blue);

                red = (int) (Math.random() * 255);
                green = (int) (Math.random() * 255);
                blue = (int) (Math.random() * 255);
                Color endColor = new Color(red, green, blue);

                GradientPaint gradientPaint = new GradientPaint(70, 70, startColor, 150, 150, endColor);
                g2d.setPaint(gradientPaint);
                g2d.fillOval(70, 70, 100, 100);
            }
        });

        jFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        jFrame.setSize(500,500);
        jFrame.setVisible(true);
    }
    /**
     *內部類  LabelListenner,按鈕lableButton的事件
     */
    class LabelListenner implements ActionListener {

        @Override
        public void actionPerformed(ActionEvent e) {
            jLabel.setText("奧，點選！！！");
        }

    }
    /**
     *內部類  ColorListenner,按鈕colorButton的事件
     */
    class ColorListenner implements ActionListener {

        @Override
        public void actionPerformed(ActionEvent e) {
            jFrame.repaint();
        }

    }
}

效果展示 ：