當用setUndecorated(true) 後 JFrame去掉標題欄後就得自己寫拖拽和拉伸功能了。

下面是效果圖，我的截圖軟體不能夠擷取除系統預設游標外的游標，所以各個方向游標變化在圖中沒有體現

程式碼如下：

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

/**
 * 窗體拖拽和拉伸
 */
public class winReSizeDemo {
    private JFrame jf;
    public winReSizeDemo(){
        jf=new JFrame();
        jf.setUndecorated(true);//去標邊界和標題欄
        jf.setLocationRelativeTo(null);//視窗置中
        jf.setSize(400,400);
        jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        reSizeEvent dg = new reSizeEvent(jf);
        /**新增兩個監聽器**/
        jf.addMouseListener(dg);
        jf.addMouseMotionListener(dg);
        jf.setVisible(true);
    }
    public static void main(String [] args){
        new winReSizeDemo();
    }
}
 

import javax.swing.*;
import java.awt.*;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
/**
 * 實現視窗各個方向拉伸以及拖動。
 */
public class reSizeEvent extends MouseAdapter{
    public JFrame jf;
    private Point prePos,curPos,jfPos;
    private static final double BREADTH = 15.0;//邊界拉伸範圍
    private  int dragType;
    private static final int DRAG_MOVE = 1;
    private static final int DRAG_UP = 2;
    private static final int DRAG_UPLEFT = 3;
    private static final int DRAG_UPRIGHT = 4;
    private static final int DRAG_LEFT = 5;
    private static final int DRAG_RIGHT = 6;
    private static final int DRAG_BOTTOM = 7;
    private static final int DRAG_BOTTOMLEFT = 8;
    private static final int DRAG_BOTTOMRIGHT = 9;
    public reSizeEvent(JFrame jf){
        this.jf = jf;
    }
    @Override
    public void mousePressed(MouseEvent e){
        prePos = e.getLocationOnScreen();
    }
    @Override
    public void mouseMoved(MouseEvent e){
        areaCheck(e.getPoint());
    }
    @Override
    public void mouseDragged(MouseEvent e){
        curPos = e.getLocationOnScreen();
        jfPos = jf.getLocation();
        dragAction();
        prePos = curPos;
    }
    private void dragAction(){
        switch(dragType){
            case DRAG_MOVE:
                jf.setLocation(jfPos.x+curPos.x-prePos.x,
                        jfPos.y+curPos.y-prePos.y);
                break;
            case DRAG_UP://x位置不變，y位置變化，並且Height變化
                jf.setLocation(jfPos.x,
                        jfPos.y+curPos.y-prePos.y);
                jf.setSize(jf.getWidth(), jf.getHeight()-(curPos.y-prePos.y));
                break;
            case DRAG_LEFT://y位置不變，x位置變化，width變化
                jf.setLocation(jfPos.x+curPos.x-prePos.x,
                        jfPos.y);
                jf.setSize(jf.getWidth()-(curPos.x-prePos.x), jf.getHeight());
                break;
            case DRAG_RIGHT://x,y位置不變，width變化
                jf.setLocation(jfPos.x,
                        jfPos.y);
                jf.setSize(jf.getWidth()+(curPos.x-prePos.x), jf.getHeight());
                break;
            case DRAG_BOTTOM://x,y位置不變，Height變化
                jf.setLocation(jfPos.x,
                        jfPos.y);
                jf.setSize(jf.getWidth(), jf.getHeight()+(curPos.y-prePos.y));
                break;
            case DRAG_UPLEFT://x,y位置均變化，h,w均變化
                jf.setLocation(jfPos.x+curPos.x-prePos.x,
                        jfPos.y+curPos.y-prePos.y);
                jf.setSize(jf.getWidth()-(curPos.x-prePos.x), jf.getHeight()-(curPos.y-prePos.y));
                break;
            case DRAG_BOTTOMRIGHT://x,y位置均不變，h,w變化
                jf.setLocation(jfPos.x,
                        jfPos.y);
                jf.setSize(jf.getWidth()+(curPos.x-prePos.x), jf.getHeight()+(curPos.y-prePos.y));
                break;
            case DRAG_UPRIGHT://x位置不變，y,w,h變化
                jf.setLocation(jfPos.x,
                        jfPos.y+curPos.y-prePos.y);
                jf.setSize(jf.getWidth()+(curPos.x-prePos.x), jf.getHeight()-(curPos.y-prePos.y));
                break;
            case DRAG_BOTTOMLEFT://y不變，xwh變化
                jf.setLocation(jfPos.x+curPos.x-prePos.x,
                        jfPos.y);
                jf.setSize(jf.getWidth()-(curPos.x-prePos.x), jf.getHeight()+(curPos.y-prePos.y));
                break;
            default:
                break;
        }
    }
    private boolean areaCheck(Point p){
        if(p.getX()<=BREADTH && p.getY()<=BREADTH){
            dragType = DRAG_UPLEFT;
            jf.setCursor(new Cursor(Cursor.NW_RESIZE_CURSOR));
        }else if(p.getX()>BREADTH
                && p.getX()<(jf.getWidth()-BREADTH)
                && p.getY()<=BREADTH){
            dragType = DRAG_UP;
            jf.setCursor(new Cursor(Cursor.N_RESIZE_CURSOR));
        }else if(p.getX()>=(jf.getWidth()-BREADTH) && p.getY()<=BREADTH){
            dragType = DRAG_UPRIGHT;
            jf.setCursor(new Cursor(Cursor.NE_RESIZE_CURSOR));
        }else if(p.getX()<=BREADTH
                && p.getY()<(jf.getHeight()-BREADTH)
                && p.getY()>BREADTH){
            dragType = DRAG_LEFT;
            jf.setCursor(new Cursor(Cursor.W_RESIZE_CURSOR));
        }else if(p.getX()>=(jf.getWidth()-BREADTH)
                && p.getY()<(jf.getHeight()-BREADTH)
                && p.getY()>BREADTH){
            dragType = DRAG_RIGHT;
            jf.setCursor(new Cursor(Cursor.E_RESIZE_CURSOR));
        }else if(p.getX()<=BREADTH
                && p.getY()>=(jf.getHeight()-BREADTH)){
            dragType = DRAG_BOTTOMLEFT;
            jf.setCursor(new Cursor(Cursor.SW_RESIZE_CURSOR));
        }else if(p.getX()>BREADTH
                && p.getX()<(jf.getWidth()-BREADTH)
                && p.getY()>=(jf.getHeight()-BREADTH)){
            dragType = DRAG_BOTTOM;
            jf.setCursor(new Cursor(Cursor.S_RESIZE_CURSOR));
        }else if(p.getX()>=(jf.getWidth()-BREADTH)
                && p.getY()>=(jf.getHeight()-BREADTH)){
            dragType = DRAG_BOTTOMRIGHT;
            jf.setCursor(new Cursor(Cursor.SE_RESIZE_CURSOR));
        }else{
            dragType = DRAG_MOVE;
            jf.setCursor(new Cursor(Cursor.MOVE_CURSOR));
            return false;
        }
        return true;
    }
}