JavaSwing中的重繪

1.重繪概念

　　　　如果未重繪，當界面發生形狀大小改變的時候，界面上面已經畫的圖形會消失。重繪后，會將之前畫的圖形還原。

2.重繪調用的方法

　　當界面大小發生改變的時候，會自動回調paint方法。顯示調用repaint方法會自動調用paint方法。

3.具體用法

　　每個組件或者窗體都有paint方法，想重繪哪個組件的paint方法，就重寫哪個組件的paint。

4.關於repaint方法

　　由於自己類本身沒有repaint方法，調用repaint方法會調用父類的repaint方法。父類的repaint方法會調用子類的paint方法。

5.匿名內部類

　　MouseAdapter mouseListener = new MouseAdapter(){

　　　　

　　};

　　匿名內部類，實際上已經發生了繼承，並且已經發生了向上轉型，寫在里面的方法相當於重寫。

6.注意事項

　　不要創建多個窗體，使用同一個窗體。

7.總結

　　一切方法都是由對象調用的，直接寫repait()方法，也是直接由該類的this對象調用的。同理，一切屬性都是由對象調用的。

　　探索能力有待提升。

8.代碼

DrawUI.java

import java.awt.FlowLayout;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;

import javax.swing.JButton;
import javax.swing.JFrame;

public class DrawUI extends JFrame{
    Graphics g;
    Shape[] shapes = new Shape[500];
    int count = 0;
    String type;
    
    ActionListener actionLisener = new ActionListener() {

        @Override
        public void actionPerformed(ActionEvent e) {
            // TODO Auto-generated method stub
            type = e.getActionCommand();
            System.out.println("type    "+type);
            if("清屏".equals(type)) {
                shapes = new Shape[500];
                count = 0;
                System.out.println("清屏"+count);
                repaint();
            }
        }
        
    };
    
    MouseAdapter mouseListener = new MouseAdapter(){
        int x1,y1,x2,y2;
        public void mousePressed(MouseEvent e) {
            x1 = e.getX();
            y1 = e.getY();
        }
        
        public void mouseReleased(MouseEvent e) {
            x2 = e.getX();
            y2 = e.getY();
            
            if("畫直線".equals(type)) {
                g.drawLine(x1, y1, x2, y2);
                shapes[count] = new Shape(x1,y1,type);
                shapes[count].x2 = x2;
                shapes[count].y2 = y2;
                System.out.println("count    "+count);
                count++;
            }else if("畫圓".equals(type)) {
                g.drawOval(x2, y2, 40, 40);
                shapes[count] = new Shape(x2,y2,type);
                shapes[count].width = 40;
                shapes[count].height = 40;
                System.out.println("count    "+count);
                count++;
            }
            
        }
    };
    
    
    
    public void init() {
        JFrame jf = this;
        jf.setSize(1500,1000);
        jf.setLocationRelativeTo(null);
        jf.setDefaultCloseOperation(3);
        jf.setLayout(new FlowLayout());
        JButton btn1 = new JButton("畫直線");
        JButton btn2 = new JButton("畫圓");
        JButton btn3 = new JButton("清屏");
        JButton btn4 = new JButton("按鈕重繪") {
            public void paint(Graphics g) {
                super.paint(g);
                g.drawLine(0, 0, 10, 20);
                if(count>2)
                    g.drawOval(0, 0, 30, 40);
            }
        };
        jf.add(btn1);
        jf.add(btn2);
        jf.add(btn3);
        jf.add(btn4);
        
        jf.setVisible(true);
        
        g = jf.getGraphics();
        
        jf.addMouseListener(mouseListener);
        btn1.addActionListener(actionLisener);
        btn2.addActionListener(actionLisener);
        btn3.addActionListener(actionLisener);
    }
    
    
    public void paint(Graphics g) {
        super.paint(g);
        for(int i=0;i<count;i++) {
            Shape shape = shapes[i];
            if(shape.type.equals("畫直線")) {
                g.drawLine(shape.x1, shape.y1,shape.x2, shape.y2);
            //    System.out.println("畫直線");
            }else if(shape.type.equals("畫圓")){
                g.drawOval(shape.x1, shape.y1, shape.width, shape.height);
            //    System.out.println("畫圓");
            }
        }
    }
    
    
    
    public static void main(String[] args) {
        new DrawUI().init();
    }

}

 Shape.java

public class Shape {
    int x1,y1,x2,y2;
    String type;
    int width;
    int height;

    public Shape(int x1, int y1,String type) {
        super();
        this.x1 = x1;
        this.y1 = y1;
        this.type = type;
    }

}

 

 

 

9.附錄

A.java

package p;

public class A {
    public void repaint() {
        System.out.println("Arepaint");
        paint();
    }
    
    public void paint() {
        System.out.println("Apaint");
    }
}

 

B.java

package p;

public class B extends A{

    public void paint() {
        System.out.println("Bpaint");
    }
}

 

 

Test.java

package p;

public class Test {

    public static void main(String[] args){
        A a = new B();
        a.repaint();   //輸出   Arepaint    Bpaint

 } 10 
}