蘭州大學 java實驗11 設計實驗

設計一個動畫程序，在圖片移動的同時變換不同的圖片，同時垂直線和水平線不斷延長，必須使用多線程的方式實現。

實現代碼：

import java.awt.*;
import java.io.*;
import javax.imageio.ImageIO;
import javax.swing.*;

class MainClass extends JPanel implements Runnable{
	private Image[] im=new Image[3];
	private int i=0;
	private int X=100,Y=90;
	Thread thread1;
	
	public MainClass() {
		try{
			for(int j=0;j<3;j++)
				im[j]=ImageIO.read(new File("image/"+j+".png"));
			}catch(Exception e){
			System.out.println("error");
		}
		this.start();
	}
	public void random(){
		X=(int)(Math.random()*600);
		Y=(int)(Math.random()*400);
	}
	public void start(){
		thread1=new Thread(this);
		thread1.start();
	}
	public void run(){		
		while(true){
			try{
				Thread.sleep((int)(Math.random()*2000));
			}catch(InterruptedException e){}
			this.random();
			repaint();		
		}
	}
	public void paint(Graphics g) {
		super.paint(g);
		if(i==3)i=0;
		g.drawImage(im[i],X,Y,44,44,this);//圖片錕斤拷錕斤拷錕斤拷爲44*44 錕斤拷錕斤拷一錕斤拷錕斤拷錕轎匡拷爲44*44錕斤拷錕斤拷錕斤拷錕斤拷錕斤拷示 					
		g.drawLine(X+22,0,X+22,Y);
		g.drawLine(0,Y+22,X,Y+22);
		i++;
	}
}
public class myFrame extends JFrame{
	public static void main(String[] args){
		myFrame myframe=new myFrame();
		MainClass mypanel=new MainClass();
		myframe.add(mypanel);
		myframe.setSize(700,500);
		myframe.setVisible(true);
		myframe.setDefaultCloseOperation(EXIT_ON_CLOSE);
	}

 

}

 

其中，public void paint(Graphics g)必須調用super.paint(),否則將會出現下面所示的情況：

 

從java JDK1.8.0_73的源碼javax\swing\JComponent.java 中找到public void paint(Graphcis g)的實現代碼如下：

    public void paint(Graphics g) {
        boolean shouldClearPaintFlags = false;

        if ((getWidth() <= 0) || (getHeight() <= 0)) {
            return;
        }

        Graphics componentGraphics = getComponentGraphics(g);
        Graphics co = componentGraphics.create();
        try {
            RepaintManager repaintManager = RepaintManager.currentManager(this);
            Rectangle clipRect = co.getClipBounds();
            int clipX;
            int clipY;
            int clipW;
            int clipH;
            if (clipRect == null) {
                clipX = clipY = 0;
                clipW = getWidth();
                clipH = getHeight();
            }
            else {
                clipX = clipRect.x;
                clipY = clipRect.y;
                clipW = clipRect.width;
                clipH = clipRect.height;
            }

            if(clipW > getWidth()) {
                clipW = getWidth();
            }
            if(clipH > getHeight()) {
                clipH = getHeight();
            }

            if(getParent() != null && !(getParent() instanceof JComponent)) {
                adjustPaintFlags();
                shouldClearPaintFlags = true;
            }

            int bw,bh;
            boolean printing = getFlag(IS_PRINTING);
            if (!printing && repaintManager.isDoubleBufferingEnabled() &&
                !getFlag(ANCESTOR_USING_BUFFER) && isDoubleBuffered() &&
                (getFlag(IS_REPAINTING) || repaintManager.isPainting()))
            {
                repaintManager.beginPaint();
                try {
                    repaintManager.paint(this, this, co, clipX, clipY, clipW,
                                         clipH);
                } finally {
                    repaintManager.endPaint();
                }
            }
            else {
                // Will ocassionaly happen in 1.2, especially when printing.
                if (clipRect == null) {
                    co.setClip(clipX, clipY, clipW, clipH);
                }

                if (!rectangleIsObscured(clipX,clipY,clipW,clipH)) {
                    if (!printing) {
                        paintComponent(co);
                        paintBorder(co);
                    }
                    else {
                        printComponent(co);
                        printBorder(co);
                    }
                }
                if (!printing) {
                    paintChildren(co);
                }
                else {
                    printChildren(co);
                }
            }
        } finally {
            co.dispose();
            if(shouldClearPaintFlags) {
                setFlag(ANCESTOR_USING_BUFFER,false);
                setFlag(IS_PAINTING_TILE,false);
                setFlag(IS_PRINTING,false);
                setFlag(IS_PRINTING_ALL,false);
            }
        }
    }