The Java Tutorials have been written for JDK 8. Examples and practices described in this page don't take advantage of improvements introduced in later releases and might use technology no longer available.
See Java Language Changes for a summary of updated language features in Java SE 9 and subsequent releases.
See JDK Release Notes for information about new features, enhancements, and removed or deprecated options for all JDK releases.
Mouse-motion events notify when the user uses the mouse (or a similar input device) to move the onscreen cursor. For information on listening for other kinds of mouse events, such as clicks, see How to Write a Mouse Listener. For information on listening for mouse-wheel events, see How to Write a Mouse Wheel Listener.
If an application requires the detection of both mouse events and mouse-motion events, use the
MouseInputAdapter
class, which implements the
MouseInputListener
a convenient interface that implements both the MouseListener
and MouseMotionListener
interfaces.
Alternatively, use the corresponding
MouseAdapter
AWT class, which implements the MouseMotionListener
interface, to create a MouseMotionEvent
and override the methods for the specific events.
The following demo code contains a mouse-motion listener. This demo is exactly the same as the demo described in the How to Write a Mouse Listener section, except for substituting the MouseMotionListener
interface for the MouseListener
interface. Additionally, MouseMotionEventDemo implements the mouseDragged
and mouseMoved
methods instead of the mouse listener methods, and displays coordinates instead of numbers of clicks.
You can find the demo's code in
MouseMotionEventDemo.java
and
BlankArea.java
. The following code snippet from MouseMotionEventDemo
implements the mouse-motion event handling:
public class MouseMotionEventDemo extends JPanel implements MouseMotionListener { //...in initialization code: //Register for mouse events on blankArea and panel. blankArea.addMouseMotionListener(this); addMouseMotionListener(this); ... } public void mouseMoved(MouseEvent e) { saySomething("Mouse moved", e); } public void mouseDragged(MouseEvent e) { saySomething("Mouse dragged", e); } void saySomething(String eventDescription, MouseEvent e) { textArea.append(eventDescription + " (" + e.getX() + "," + e.getY() + ")" + " detected on " + e.getComponent().getClass().getName() + newline); } }
The SelectionDemo example, draws a rectangle illustrating the user's current dragging. To draw the rectangle, the application must implement an event handler for three kinds of mouse events: mouse presses, mouse drags, and mouse releases. To be informed of all these events, the handler must implement both the MouseListener
and MouseMotionListener
interfaces, and be registered as both a mouse listener and a mouse-motion listener. To avoid having to define empty methods, the handler doesn't implement either listener interface directly. Instead, it extends MouseInputAdapter
, as the following code snippet shows.
...//where initialization occurs: MyListener myListener = new MyListener(); addMouseListener(myListener); addMouseMotionListener(myListener); ... private class MyListener extends MouseInputAdapter { public void mousePressed(MouseEvent e) { int x = e.getX(); int y = e.getY(); currentRect = new Rectangle(x, y, 0, 0); updateDrawableRect(getWidth(), getHeight()); repaint(); } public void mouseDragged(MouseEvent e) { updateSize(e); } public void mouseReleased(MouseEvent e) { updateSize(e); } void updateSize(MouseEvent e) { int x = e.getX(); int y = e.getY(); currentRect.setSize(x - currentRect.x, y - currentRect.y); updateDrawableRect(getWidth(), getHeight()); Rectangle totalRepaint = rectToDraw.union(previouseRectDrawn); repaint(totalRepaint.x, totalRepaint.y, totalRepaint.width, totalRepaint.height); } }
The MouseMotionListener Interface
The corresponding adapter classes are
MouseMotionAdapter
and
MouseAdapter
.
Method | Purpose |
---|---|
mouseDragged(MouseEvent) | Called in response to the user moving the mouse while holding a mouse button down. This event is fired by the component that fired the most recent mouse-pressed event, even if the cursor is no longer over that component. |
mouseMoved(MouseEvent) | Called in response to the user moving the mouse with no mouse buttons pressed. This event is fired by the component that's currently under the cursor. |
Each mouse-motion event method has a single parameter — and it's not called MouseMotionEvent
! Instead, each mouse-motion event method uses a MouseEvent
argument. See The MouseEvent API for information about using MouseEvent
objects.
The following table lists the examples that use mouse-motion listeners.
Example | Where Described | Notes |
---|---|---|
MouseMotionEventDemo |
This section | Reports all mouse motion events that occur within a blank panel to demonstrate the circumstances under which mouse motion events are fired. |
LayeredPaneDemo andLayeredPaneDemo2 |
How to Use Layered Panes | Moves an image of Duke around within a layered pane in response to mouse motion events. |
SelectionDemo |
Lets the user drag a rectangle to select a portion of an image. Uses a subclass of MouseInputAdapter to listen to both mouse events and mouse-motion events. |
|
GlassPaneDemo |
How to Use Root Panes | Uses a subclass of MouseInputAdapter to listen to mouse events and mouse-motion events on the root pane's glass pane. Redispatches the events to underlying components. |
ScrollDemo |
How to Use Scroll Panes | The label subclass, ScrollablePicture, uses a mouse-motion listener to allow the user to scroll the picture even when the user drags the cursor outside the window. |