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 [email protected]
     * @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
	 */
	@Override
	public 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);
	}

	@Override
	public 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);
	}

	@Override
	public 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());
	    }
	}

	@Override
	public void mouseExited(MouseEvent e) {
	    if (!this.dragging) {
		Window win = (Window) e.getSource();
		win.setCursor(Cursor.getDefaultCursor());
	    }
	}

	@Override
	public 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
	 */
	@Override
	public 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。