不对窗体进行边框装饰后，实现对鼠标事件的监控

如果对JFrame调用了方法setUndecorated(true);，那么窗体将没有标题栏，以及标题栏上的关闭、最大化、最小化菜单了。

这是要实现对鼠标的监控就必须自己手动去添加鼠标监听。下面代码就是实现对鼠标的监听，从而改变窗体的大小。（这里没有实现添加关闭、最大化、最小化按钮）

 /**     * 监听鼠标事件,实现鼠标对窗体大小的改变     *      * @author mengke     * @email [e-mail]     * @version 1.0     * @date 2012-2-25 下午10:45:48     */    private class MouseInputHandler extends MouseInputAdapter {private static final int CORNER_DRAG_WIDTH = 10;private static final int BORDER_DRAG_THICKNESS = 5;/** 是否可移动窗体 */private boolean isMovingWindow;private boolean dragging;private int dragCursor;private int dragOffsetX;private int dragOffsetY;private int dragWidth;private int dragHeight;private MouseInputHandler() {}/** * 只处理鼠标左键按下操作 */@Overridepublic void mousePressed(MouseEvent e) {    if (!SwingUtilities.isLeftMouseButton(e)) {return;    }    Point dragWindowOffset = e.getPoint();    Window win = (Window) e.getSource();    this.dragging = true;    if (win != null) {/** 将窗体置前 */win.toFront();    }    Frame frame = (win instanceof Frame) ? (Frame) win : null;    int frameState = frame != null ? frame.getExtendedState()    : Frame.NORMAL;    if (((frame != null) && ((frameState & Frame.MAXIMIZED_BOTH) == 0))) {this.isMovingWindow = true;this.dragOffsetX = dragWindowOffset.x;this.dragOffsetY = dragWindowOffset.y;    }    if (!this.isMovingWindow && frame != null && frame.isResizable()    && ((frameState & Frame.MAXIMIZED_BOTH) == 0)) {this.dragOffsetX = dragWindowOffset.x;this.dragOffsetY = dragWindowOffset.y;    }    this.dragWidth = win.getWidth();    this.dragHeight = win.getHeight();    this.dragCursor = getCursor(win, e);}@Overridepublic void mouseReleased(MouseEvent e) {    if (!SwingUtilities.isLeftMouseButton(e)) {return;    }    if ((this.dragCursor != Cursor.DEFAULT_CURSOR)    && (!JRoundFrame.this.isValid())) {JRoundFrame.this.validate();    }    this.dragging = false;    this.isMovingWindow = false;    this.dragCursor = Cursor.DEFAULT_CURSOR;    mouseMoved(e);}@Overridepublic void mouseMoved(MouseEvent e) {    Window win = (Window) e.getSource();    Frame frame = (win instanceof Frame) ? (Frame) win : null;    int cursor = getCursor(win, e);    if ((cursor != 0)    && (win.getBounds().contains(e.getLocationOnScreen()))    && ((frame != null) && (frame.isResizable()) && ((frame    .getExtendedState() & Frame.MAXIMIZED_BOTH) == 0))) {win.setCursor(Cursor.getPredefinedCursor(cursor));    } else {win.setCursor(Cursor.getDefaultCursor());    }}@Overridepublic void mouseExited(MouseEvent e) {    if (!this.dragging) {Window win = (Window) e.getSource();win.setCursor(Cursor.getDefaultCursor());    }}@Overridepublic void mouseDragged(MouseEvent e) {    if (!SwingUtilities.isLeftMouseButton(e)) {if (JRoundFrame.this.getBounds().contains(e.getPoint())) {    mouseMoved(e);} else {    mouseExited(e);}return;    }    Window win = (Window) e.getSource();    Point point = e.getPoint();    if (this.isMovingWindow && this.dragCursor == Cursor.DEFAULT_CURSOR) {Point eventLocationOnScreen = e.getLocationOnScreen();win.setLocation(eventLocationOnScreen.x - this.dragOffsetX,eventLocationOnScreen.y - this.dragOffsetY);    } else if (this.dragCursor != Cursor.DEFAULT_CURSOR) {Rectangle rect = win.getBounds();Rectangle startBounds = new Rectangle(rect);Dimension min = win.getMinimumSize();Dimension max = win.getMaximumSize();switch (this.dragCursor) {case Cursor.E_RESIZE_CURSOR:    adjust(rect, min, max, 0, 0, point.x    + (this.dragWidth - this.dragOffsetX) - rect.width,    0);    break;case Cursor.S_RESIZE_CURSOR:    adjust(rect, min, max, 0, 0, 0, point.y    + (this.dragHeight - this.dragOffsetY)    - rect.height);    break;case Cursor.N_RESIZE_CURSOR:    adjust(rect, min, max, 0, point.y - this.dragOffsetY, 0,    -(point.y - this.dragOffsetY));    break;case Cursor.W_RESIZE_CURSOR:    adjust(rect, min, max, point.x - this.dragOffsetX, 0,    -(point.x - this.dragOffsetX), 0);    break;case Cursor.NE_RESIZE_CURSOR:    adjust(rect, min, max, 0, point.y - this.dragOffsetY,    point.x + (this.dragWidth - this.dragOffsetX)    - rect.width, -(point.y - this.dragOffsetY));    break;case Cursor.SE_RESIZE_CURSOR:    adjust(rect, min, max, 0, 0, point.x    + (this.dragWidth - this.dragOffsetX) - rect.width,    point.y + (this.dragHeight - this.dragOffsetY)    - rect.height);    break;case Cursor.NW_RESIZE_CURSOR:    adjust(rect, min, max, point.x - this.dragOffsetX, point.y    - this.dragOffsetY, -(point.x - this.dragOffsetX),    -(point.y - this.dragOffsetY));    break;case Cursor.SW_RESIZE_CURSOR:    adjust(rect, min, max, point.x - this.dragOffsetX, 0,    -(point.x - this.dragOffsetX), point.y    + (this.dragHeight - this.dragOffsetY)    - rect.height);    break;}if (!rect.equals(startBounds)) {    win.setBounds(rect);    if (Toolkit.getDefaultToolkit().isDynamicLayoutActive()) {win.validate();JRoundFrame.this.getRootPane().repaint();    }}    }}/** * 鼠标左键点击事件 */@Overridepublic void mouseClicked(MouseEvent e) {    if (!SwingUtilities.isLeftMouseButton(e)) {return;    }    Window win = (Window) e.getSource();    Frame frame = (win instanceof Frame) ? (Frame) win : null;    Point point = e.getPoint();    int clickCount = e.getClickCount();    if ((clickCount % 2 == 0)    && (point.x <= 22)    && (point.y <= 22)    && (JRoundFrame.this.getRootPane()    .getWindowDecorationStyle() != 0)) {JRoundFrame.this.dispatchEvent(new WindowEvent(JRoundFrame.this, WindowEvent.WINDOW_CLOSING));return;    }    if (frame == null) {return;    }    int state = frame.getExtendedState();    Window fullWin = GraphicsEnvironment.getLocalGraphicsEnvironment()    .getDefaultScreenDevice().getFullScreenWindow();    if ((frame.isResizable()) && (frame != fullWin)    && (clickCount % 2 == 0)) {if ((state & Frame.MAXIMIZED_BOTH) != 0) {    frame.setExtendedState(state & 0xFFFFFFF9);} else {    frame.setExtendedState(state | Frame.MAXIMIZED_BOTH);}    }}private void adjust(Rectangle bounds, Dimension min, Dimension max,int deltaX, int deltaY, int deltaWidth, int deltaHeight) {    bounds.x += deltaX;    bounds.y += deltaY;    bounds.width += deltaWidth;    bounds.height += deltaHeight;    if (min != null) {if (bounds.width < min.width) {    int correction = min.width - bounds.width;    if (deltaX != 0) {bounds.x -= correction;    }    bounds.width = min.width;}if (bounds.height < min.height) {    int correction = min.height - bounds.height;    if (deltaY != 0) {bounds.y -= correction;    }    bounds.height = min.height;}    }    if (max != null) {if (bounds.width > max.width) {    int correction = max.width - bounds.width;    if (deltaX != 0) {bounds.x -= correction;    }    bounds.width = max.width;}if (bounds.height > max.height) {    int correction = max.height - bounds.height;    if (deltaY != 0) {bounds.y -= correction;    }    bounds.height = max.height;}    }}private int getCursor(Window win, MouseEvent e) {    int winWidth = win.getBounds().width;    int winHeight = win.getBounds().height;    Point p = e.getPoint();// e.getLocationOnScreen();    if (win.getBounds().contains(e.getLocationOnScreen())) {// 先判断四个角if (p.x - CORNER_DRAG_WIDTH < 0 && p.y - CORNER_DRAG_WIDTH < 0) {    return Cursor.NW_RESIZE_CURSOR;} else if (p.x - (winWidth - CORNER_DRAG_WIDTH) > 0&& p.y - CORNER_DRAG_WIDTH < 0) {    return Cursor.NE_RESIZE_CURSOR;} else if (p.x - CORNER_DRAG_WIDTH < 0&& p.y - (winHeight - CORNER_DRAG_WIDTH) > 0) {    return Cursor.SW_RESIZE_CURSOR;} else if (p.x - (winWidth - CORNER_DRAG_WIDTH) > 0&& p.y - (winHeight - CORNER_DRAG_WIDTH) > 0) {    return Cursor.SE_RESIZE_CURSOR;}// 判断是否在中间部分if ((p.x > BORDER_DRAG_THICKNESS && p.x < winWidth- BORDER_DRAG_THICKNESS)&& (p.y > BORDER_DRAG_THICKNESS && p.y < winHeight- BORDER_DRAG_THICKNESS)) {    return Cursor.DEFAULT_CURSOR;} else {    if (p.x - BORDER_DRAG_THICKNESS < 0) {return Cursor.W_RESIZE_CURSOR;    } else if (p.y - BORDER_DRAG_THICKNESS < 0) {return Cursor.N_RESIZE_CURSOR;    } else if (winWidth - BORDER_DRAG_THICKNESS > p.x) {return Cursor.S_RESIZE_CURSOR;    } else {return Cursor.E_RESIZE_CURSOR;    }}    }    return Cursor.DEFAULT_CURSOR;}    }

其中JRoundFrame为继承JFrame类的类。在该类的构造方法中添加该鼠标监听，就能实现鼠标对该窗体的大小的改变了。