Java學習筆記（9）：圖形介面

一：第一個圖形——按鈕

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class tx implements ActionListener {//實作ActionListener介面
    JButton button;//創建按鈕

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

    public void go()
    {
        JFrame frame = new JFrame();
       button = new JButton("click me");//按鈕上的文本顯示

        button.addActionListener(this);//向按鈕注冊

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);//在視窗關閉時結束程式

        frame.getContentPane().add(BorderLayout.CENTER,button);//將按鈕放在中心
        
        frame.setSize(300,300);//設定出現在你螢屏的那個視窗多大

        frame.setVisible(true);
    }
    public void actionPerformed(ActionEvent event)//actionPerformed不能改喔
    {
        button.setText("ywq i love you");
    }
}

二：第二個圖形——雙重按鈕加變色變文本內容

/*目標： 設定兩個獨立按鈕：需要分別創建不同的指令接受類 class 類名 implements ActionListener{}
 //實作label的按鈕接受資訊
    class LabelListener implements ActionListener
    {
        public void actionPerformed(ActionEvent event)
        {
        }
    }
    //實作改變顏色的按鈕接受資訊
    class ColorListener implements ActionListener
    {
        public void actionPerformed(ActionEvent event)
        {
        }
    } 
*/

//圖形設定及列印，ht類
import javax.swing.*;
import java.awt.*;

public class ht extends JPanel{  //注意要繼承JPanel
    public void paintComponent(Graphics g){
        Graphics2D g2d = (Graphics2D) g;

        //設定隨機顏色
        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);

        //設定隨機顏色
        red = (int) (Math.random()*255);
        green = (int) (Math.random()*255);
        blue = (int) (Math.random()*255);
        Color endColor = new Color(red,green,blue);

        //設定漸變
        GradientPaint gradient = new GradientPaint(70,70,startColor,150,150,endColor);
        g2d.setPaint(gradient);
        //畫出圖形
        g2d.fillOval(70,70,100,100);
    }
}

//主類
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class gui3c{
    public static int i = 1;

    public static int getI() {
        return i;
    }

    public static void setI(int i) {
        gui3c.i = i+1;
    }

    JFrame frame;
    JLabel label;
    public static void main(String[] args) {
        gui3c gui = new gui3c();
        gui.go();
    }

    public void go()
    {
        //常規設定
        frame =new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        //創建color按鈕
        JButton colorButton = new JButton("change color");
        colorButton.addActionListener(new ColorListener());

        //創建label按鈕
        JButton labelButton = new JButton("change label");
        labelButton.addActionListener(new LabelListener());

        //設定label
        ht draw =new ht();
        label = new JLabel("i am a label");

        //將label，label按鈕，color按鈕和ht中的圖形加入frame
        frame.getContentPane().add(BorderLayout.SOUTH,colorButton);
        frame.getContentPane().add(BorderLayout.EAST,labelButton);
        frame.getContentPane().add(BorderLayout.CENTER,draw);
        frame.getContentPane().add(BorderLayout.WEST,label);

        //設定圖形的大小
        frame.setSize(300,300);
        frame.setVisible(true);
    }

    //實作label的按鈕
    class LabelListener implements ActionListener
    {
        public void actionPerformed(ActionEvent event)
        {
            //改變文本內容
            label.setText("于文晴小寶貝我愛你"+"*"+i);
            setI(i);
        }
    }
    //實作改變顏色的按鈕
    class ColorListener implements ActionListener
    {
        public void actionPerformed(ActionEvent event)
        {
            //每次repaint（）都會執行paintComponent里面的指令
            frame.repaint();
        }
    }
}

值得注意的是：
1.JFrame的用法
2.按鈕創建JButton，文本創建JLabel
單個按鈕與多個按鈕ActionListener的寫法不同