java 实现图片的任意拖动

import javax.swing.*;


import java.awt.*;


import java.awt.event.*;


public class PanelTest extends JPanel


{


static int frame_width = 600;


static int frame_height = 300;





PicPanel pic = null;


private int pic_x;


private int pic_y;





//前一个位置


int begin_x = 0;


int begin_y = 0;





boolean inThePic = false;







public PanelTest()


{


pic = new PicPanel("pic.jpg");


setLayout(null);


add(pic);





pic_x = (int)((frame_width - pic.getWidth())/2);


pic_y = (int)((frame_height - pic.getHeight())/2);





pic.setLocation(pic_x, pic_y); //定位





//鼠标动作 监听器 注册


addMouseListener(


new MouseAdapter()


{


public void mousePressed(MouseEvent e)


{


//检测 落点 是否在图片上,只有落点在图片上时 才起作用


if(inPicBounds(e.getX(), e.getY()))


{


begin_x = e.getX();


begin_y = e.getY();


inThePic = true;


}


//记录当前坐标


}


//释放


public void mouseReleased(MouseEvent e)


{


inThePic = false;


}


}


);





//鼠标移动 监听器 注册


addMouseMotionListener(


new MouseMotionAdapter()


{


public void mouseDragged(MouseEvent e)


{


if(inThePic && checkPoint(e.getX(),e.getY()))


{


//边界 检查


pic_x =pic_x - (begin_x - e.getX());


pic_y =pic_y - (begin_y - e.getY());


//System.out.println("pic_x=" + pic_x);


begin_x = e.getX();


begin_y = e.getY();


pic.setLocation(pic_x, pic_y);


}


}


}


);


}


//-------------帮助方法-----------------//


//检测 点(px,py) 是否在图片上


private boolean inPicBounds(int px,int py)


{


if(px >= pic_x && px <= pic_x + pic.getWidth() &&


py >= pic_y && py <= pic_y + pic.getHeight())


return true;


else


return false;


}





//越界 检查


private boolean checkPoint(int px, int py)


{


if(px <0 || py <0)


return false;


if(px >getWidth() || py > getHeight())


return false;


return true;


}





public static void main(String[] args)


{


JPanel jpanel = new PanelTest();


JFrame jframe = new JFrame("图片拖动");


jframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);


jframe.getContentPane().add(jpanel);


jframe.setSize(frame_width, frame_height);


jframe.setVisible(true);


}


}


//图片面板,只是用来放置图片


class PicPanel extends JPanel


{


int p_width = 0;


int p_height = 0;


Image im = null;





int i = 0; //temp var


public PicPanel(String picName)


{


ImageIcon imageIcon = new ImageIcon(picName);


im = imageIcon.getImage();





p_width = imageIcon.getIconWidth();


p_height = imageIcon.getIconHeight();


setBounds(0,0,p_width, p_height);


}





public void paint(Graphics g)


{


g.drawImage(im,0,0,p_width,p_height,null);


}


}