在用戶拖動鼠標時收聽JFrame調整大小事件？

Question

當用戶單擊JFrame的角落以調整大小並拖動鼠標時，JFrame將根據用戶拖動的鼠標的當前位置重新繪製。你怎麼能聽這些事件？

下面是我所目前正在嘗試：

public final class TestFrame extends JFrame { 
    public TestFrame() { 
     this.addComponentListener(new ComponentAdapter() { 
      public void componentResized(ComponentEvent e) { 
       // This is only called when the user releases the mouse button. 
       System.out.println("componentResized"); 
      } 
     }); 
    } 

    // These methods do not appear to be called at all when a JFrame 
    // is being resized. 
    @Override 
    public void setSize(int width, int height) { 
     System.out.println("setSize"); 
    } 

    @Override 
    public void setBounds(Rectangle r) { 
     System.out.println("setBounds A"); 
    } 

    @Override 
    public void setBounds(int x, int y, int width, int height) { 
     System.out.println("setBounds B"); 
    } 
} 

如何確定並限制用戶如何調整其大小的窗口（基於窗口的當前長寬比），因爲他們周圍拖動鼠標周圍？

Answer 1

你可能需要重寫像validate（不要忘記調用超級）。當然，如果您使用窗口系統配置爲拖動輪廓線，這仍然可能不起作用。

Answer 2

您可以添加組件偵聽器，並實現這樣的功能的componentResized：

JFrame component = new JFrame("My Frame"); 

component.addComponentListener(new ComponentAdapter() 
{ 
     public void componentResized(ComponentEvent evt) { 
      Component c = (Component)evt.getSource(); 
      //........ 
     } 
}); 

編輯：顯然，對於JFrame的，上的componentResized事件被掛在事件的mouseReleased。這就是爲什麼當釋放鼠標按鈕時調用該方法的原因。

實現所需目標的一種方法是添加一個覆蓋整個JFrame區域的JPanel。然後將componentListener添加到JPanel（即使鼠標仍在拖動時，也會調用componentResized for JPanel）。當您的框架調整大小時，您的面板也將調整大小。

我知道，這不是最優雅的解決方案，但它的工作原理！

Answer 3

public class MouseDrag extends Component implements MouseListener, 
    MouseMotionListener { 
    /** The Image we are to paint */ 
    Image curImage; 

    /** Kludge for showStatus */ 
    static Label status; 

    /** true if we are in drag */ 
    boolean inDrag = false; 

    /** starting location of a drag */ 
    int startX = -1, startY = -1; 

    /** current location of a drag */ 
    int curX = -1, curY = -1; 

    // "main" method 
    public static void main(String[] av) { 
    JFrame f = new JFrame("Mouse Dragger"); 
    Container cp = f.getContentPane(); 

    if (av.length < 1) { 
     System.err.println("Usage: MouseDrag imagefile"); 
     System.exit(1); 
    } 
    Image im = Toolkit.getDefaultToolkit().getImage(av[0]); 

    // create a MouseDrag object 
    MouseDrag j = new MouseDrag(im); 

    cp.setLayout(new BorderLayout()); 
    cp.add(BorderLayout.NORTH, new Label(
     "Hello, and welcome to the world of Java")); 
    cp.add(BorderLayout.CENTER, j); 
    cp.add(BorderLayout.SOUTH, status = new Label()); 
    status.setSize(f.getSize().width, status.getSize().height); 
    f.pack(); 
    f.setVisible(true); 
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
    } 

    // "Constructor" - creates the object 
    public MouseDrag(Image i) { 
    super(); 
    curImage = i; 
    setSize(300, 200); 
    addMouseListener(this); 
    addMouseMotionListener(this); 
    } 

    public void showStatus(String s) { 
    status.setText(s); 
    } 

    // Five methods from MouseListener: 
    /** Called when the mouse has been clicked on a component. */ 
    public void mouseClicked(MouseEvent e) { 
    } 

    /** Called when the mouse enters a component. */ 
    public void mouseEntered(MouseEvent e) { 
    } 

    /** Called when the mouse exits a component. */ 
    public void mouseExited(MouseEvent e) { 
    } 


    // And two methods from MouseMotionListener: 
    public void mouseDragged(MouseEvent e) { 
    Point p = e.getPoint(); 
    // System.err.println("mouse drag to " + p); 
    showStatus("mouse Dragged to " + p); 
    curX = p.x; 
    curY = p.y; 
    if (inDrag) { 
     repaint(); 
    } 
    } 

    public void paint(Graphics g) { 
    int w = curX - startX, h = curY - startY; 
    Dimension d = getSize(); 
    g.drawImage(curImage, 0, 0, d.width, d.height, this); 
    if (startX < 0 || startY < 0) 
     return; 
    System.err.println("paint:drawRect @[" + startX + "," + startY 
     + "] size " + w + "x" + h); 
    g.setColor(Color.red); 
    g.fillRect(startX, startY, w, h); 
    } 

} 

Answer 4

另一個解決方法（這是非常相似，Alex的，但有點更簡單）是從JFrame的根窗格，而不是聽事件：

public final class TestFrame extends JFrame { 
    public TestFrame() { 
     this.getRootPane().addComponentListener(new ComponentAdapter() { 
      public void componentResized(ComponentEvent e) { 
       // This is only called when the user releases the mouse button. 
       System.out.println("componentResized"); 
      } 
     }); 
    } 
} 

根據其他實施細節，可能會改變根窗格。如果這是可能性，那麼你可以覆蓋setRootPane()並處理。由於setRootPane()受保護，只能從構造函數調用，所以不太可能需要這樣做。