Package codedraw.events

Class EventScanner

java.lang.Object
codedraw.events.EventScanner
All Implemented Interfaces:
AutoCloseable
public class EventScanner extends Object implements AutoCloseable
The EventScanner works in the same way as a Scanner. The source of the events is specified as an argument to the constructor of the EventScanner. If multi EventScanner listen to the same CodeDraw instance/window, then the event will appear in both EventScanner.

The following example shows the current position of the mouse and the number of clicks: 

 CodeDraw cd = new CodeDraw();
 EventScanner es = new EventScanner(cd);

 int x = 0;
 int y = 0;
 int clickCount = 0;

 while (!es.isClosed()) {
     while (es.hasEventNow()) {
         if (es.hasMouseMoveEvent()) {
             MouseMoveEventArgs a = es.nextMouseMoveEvent();
             x = a.getX();
             y = a.getY();
         }
         if (es.hasMouseClickEvent()) {
             clickCount++;
             es.nextEvent();
         }
         else {
             es.nextEvent();
         }
     }

     cd.clear();
     cd.drawText(100, 100, "Position: " + x + " " + y + "\nClick: " + clickCount);
     cd.show();
 }
This example first check if there are events available. If there are, they get processed until there are no more events available. Events that are not moves or clicks are ignored. Once the events are processed the x/y position and clickCount are shown. This continues in a loop until the user closes the window.

The EventScanner automatically closes when the CodeDraw window is closed. The remaining events can still be consumed when the EventScanner is closed, but no new events will appear.

  • Constructor Details

    • EventScanner

      public EventScanner(CodeDraw codeDraw)
      Creates a new EventScanner. Read the class documentation for a detailed explanation.
      Parameters:
      codeDraw - the source of the events.

  • Method Details

    • waitFor

      public static <T> T waitFor(Function<EventHandler<T>,Subscription> codeDrawEvent)
      Waits until the next time the given event is triggered and then returns the event arguments as the result of this function. However, events that happen just before or after calling waitFor are lost. That means if events happen in between waitFor calls these events will be lost. To prevent that create an EventScanner object and use that object.

      Example: 
      
 MouseClickEventArgs args = EventScanner.waitFor(codeDraw::onMouseClick);
 // use args here
      Type Parameters:
      T - a type of event argument.
      Parameters:
      codeDrawEvent - a CodeDraw Event.
      Returns:
      The event argument.

    • hasEventNow

      public boolean hasEventNow()
      Doesn't wait until the next event is available, but instead returns immediately. If there is currently an event available returns true otherwise false.
      Returns:
      whether there are currently events available

    • hasEvent

      public boolean hasEvent()
      Waits until the next event is available. Returns false if there are no more events.
      Returns:
      whether there are more events available

    • hasMouseClickEvent

      public boolean hasMouseClickEvent()
      Waits until the next mouse click event is available. Returns true if the next event is a mouse click event, otherwise false. The mouse click event is triggered once when a mouse button is pressed down and quickly released again.
      Returns:
      whether the next event is a mouse click event.

    • hasMouseMoveEvent

      public boolean hasMouseMoveEvent()
      Waits until the next mouse move event is available. Returns true if the next event is a mouse move event, otherwise false. The mouse move event is triggered continuously while the mouse is being moved.
      Returns:
      whether the next event is a mouse move event.

    • hasMouseDownEvent

      public boolean hasMouseDownEvent()
      Waits until the next mouse down event is available. Returns true if the next event is a mouse down event, otherwise false. The mouse down event is triggered exactly once when a mouse button is pressed down.
      Returns:
      whether the next event is a mouse down event.

    • hasMouseUpEvent

      public boolean hasMouseUpEvent()
      Waits until the next mouse up event is available. Returns true if the next event is a mouse up event, otherwise false. The mouse up event is triggered when a mouse button is released.
      Returns:
      whether the next event is a mouse up event.

    • hasMouseEnterEvent

      public boolean hasMouseEnterEvent()
      Waits until the next mouse enter event is available. Returns true if the next event is a mouse enter event, otherwise false. The mouse enter event is triggered when the mouse enters the canvas.
      Returns:
      whether the next event is a mouse enter event.

    • hasMouseLeaveEvent

      public boolean hasMouseLeaveEvent()
      Waits until the next mouse leave event is available. Returns true if the next event is a mouse leave event, otherwise false. The mouse leave event is triggered when the mouse leaves the canvas.
      Returns:
      whether the next event is a mouse leave event.

    • hasMouseWheelEvent

      public boolean hasMouseWheelEvent()
      Waits until the next mouse wheel event is available. Returns true if the next event is a mouse wheel event, otherwise false. The mouse wheel event is triggered each time the mouse wheel is turned.
      Returns:
      whether the next event is a mouse wheel event.

    • hasKeyDownEvent

      public boolean hasKeyDownEvent()
      Waits until the next key down event is available. Returns true if the next event is a key down event, otherwise false. The key down event is triggered exactly once when a key is pressed down.
      Returns:
      whether the next event is a key down event.

    • hasKeyUpEvent

      public boolean hasKeyUpEvent()
      Waits until the next key up event is available. Returns true if the next event is a key up event, otherwise false. The key up event is triggered exactly once when a key is released.
      Returns:
      whether the next event is a key up event.

    • hasKeyPressEvent

      public boolean hasKeyPressEvent()
      Waits until the next key press event is available. Returns true if the next event is a key press event, otherwise false. The key press event is triggered continuously while a key is being held down.
      Returns:
      whether the next event is a key press event.

    • hasWindowMoveEvent

      public boolean hasWindowMoveEvent()
      Waits until the next window move event is available. Returns true if the next event is a window move event, otherwise false. The window move event is triggered every time the CodeDraw window is moved.
      Returns:
      whether the next event is a window move event.

    • hasWindowCloseEvent

      public boolean hasWindowCloseEvent()
      Waits until the next window close event is available. Returns true if the next event is a window close event, otherwise false. The window close event is triggered exactly once when the user closes the window or CodeDraw.close() is called.
      Returns:
      whether the next event is a window close event.

    • nextEvent

      public Object nextEvent()
      Waits for the next event and then returns it. Check hasEvent() or hasEventNow() before calling this function.

      In the newer java version 17+ you can use switch pattern matching to handle events. 
      
 EventScanner es = new EventScanner(codeDraw);
 while (es.hasEvent()) {
     switch (es.nextEvent()) {
         case MouseDownEventArgs a:
             System.out.println("The mouse has been pressed at x=" + a.getX() + " y=" + a.getY() + ".");
             break;
         case KeyDownEventArgs a:
             System.out.println("The " + a.getKey() + " has been pressed.");
             break;
         default:
     }
 }
      Returns:
      The event args as an object.
      Throws:
      NoSuchElementException - if there are no more events.

    • nextMouseClickEvent

      public MouseClickEventArgs nextMouseClickEvent()
      Waits for the next mouse click event and then consumes the event. The mouse click event is triggered once when a mouse button is pressed down and quickly released again. Check hasMouseClickEvent() before calling this function.
      Returns:
      a mouse click event.
      Throws:
      InputMismatchException - if the next event is not a mouse click event.
      NoSuchElementException - if there are no more events.

    • nextMouseMoveEvent

      public MouseMoveEventArgs nextMouseMoveEvent()
      Waits for the next mouse move event and then consumes the event. The mouse move event is triggered continuously while the mouse is being moved. Check hasMouseMoveEvent() before calling this function.
      Returns:
      a mouse move event.
      Throws:
      InputMismatchException - if the next event is not a mouse move event.
      NoSuchElementException - if there are no more events.

    • nextMouseDownEvent

      public MouseDownEventArgs nextMouseDownEvent()
      Waits for the next mouse down event and then consumes the event. The mouse down event is triggered exactly once when a mouse button is pressed down. Check hasMouseDownEvent() before calling this function.
      Returns:
      a mouse down event.
      Throws:
      InputMismatchException - if the next event is not a mouse down event.
      NoSuchElementException - if there are no more events.

    • nextMouseUpEvent

      public MouseUpEventArgs nextMouseUpEvent()
      Waits for the next mouse up event and then consumes the event. The mouse up event is triggered when a mouse button is released. Check hasMouseUpEvent() before calling this function.
      Returns:
      a mouse up event.
      Throws:
      InputMismatchException - if the next event is not a mouse up event.
      NoSuchElementException - if there are no more events.

    • nextMouseEnterEvent

      public MouseEnterEventArgs nextMouseEnterEvent()
      Waits for the next mouse enter event and then consumes the event. The mouse enter event is triggered when the mouse enters the canvas. Check hasMouseEnterEvent() before calling this function.
      Returns:
      a mouse enter event.
      Throws:
      InputMismatchException - if the next event is not a mouse enter event.
      NoSuchElementException - if there are no more events.

    • nextMouseLeaveEvent

      public MouseLeaveEventArgs nextMouseLeaveEvent()
      Waits for the next mouse leave event and then consumes the event. The mouse leave event is triggered when the mouse leaves the canvas. Check hasMouseLeaveEvent() before calling this function.
      Returns:
      a mouse leave event.
      Throws:
      InputMismatchException - if the next event is not a mouse leave event.
      NoSuchElementException - if there are no more events.

    • nextMouseWheelEvent

      public MouseWheelEventArgs nextMouseWheelEvent()
      Waits for the next mouse wheel event and then consumes the event. The mouse wheel event is triggered each time the mouse wheel is turned. Check hasMouseWheelEvent() before calling this function.
      Returns:
      a mouse wheel event.
      Throws:
      InputMismatchException - if the next event is not a mouse wheel event.
      NoSuchElementException - if there are no more events.

    • nextKeyDownEvent

      public KeyDownEventArgs nextKeyDownEvent()
      Waits for the next key down event and then consumes the event. The key down event is triggered exactly once when a key is pressed down. Check hasKeyDownEvent() before calling this function.
      Returns:
      a key down event.
      Throws:
      InputMismatchException - if the next event is not a key down event.
      NoSuchElementException - if there are no more events.

    • nextKeyUpEvent

      public KeyUpEventArgs nextKeyUpEvent()
      Waits for the next key up event and then consumes the event. The key up event is triggered exactly once when a key is released. Check hasKeyUpEvent() before calling this function.
      Returns:
      a key up event.
      Throws:
      InputMismatchException - if the next event is not a key up event.
      NoSuchElementException - if there are no more events.

    • nextKeyPressEvent

      public KeyPressEventArgs nextKeyPressEvent()
      Waits for the next key press event and then consumes the event. The key press event is triggered continuously while a key is being held down. Check hasKeyPressEvent() before calling this function.
      Returns:
      a key press event.
      Throws:
      InputMismatchException - if the next event is not a key press event.
      NoSuchElementException - if there are no more events.

    • nextWindowMoveEvent

      public WindowMoveEventArgs nextWindowMoveEvent()
      Waits for the next window move event and then consumes the event. The window move event is triggered every time the CodeDraw window is moved. Check hasWindowMoveEvent() before calling this function.
      Returns:
      a window move event.
      Throws:
      InputMismatchException - if the next event is not a window move event.
      NoSuchElementException - if there are no more events.

    • nextWindowCloseEvent

      public WindowCloseEventArgs nextWindowCloseEvent()
      Waits for the next window close event and then consumes the event. The window close event is triggered exactly once when the user closes the window or CodeDraw.close() is called. Check hasWindowCloseEvent() before calling this function.
      Returns:
      a window close event.
      Throws:
      InputMismatchException - if the next event is not a window close event.
      NoSuchElementException - if there are no more events.

    • close

      public void close()
      Closes the EventScanner. The EventScanner automatically closes when the CodeDraw window is closed. The remaining events can still be consumed when the EventScanner is closed, but no new events will appear.
      Specified by:
      close in interface AutoCloseable

    • isClosed

      public boolean isClosed()
      Checks whether this EventScanner is closed. The EventScanner automatically closes when the CodeDraw window is closed.
      Returns:
      whether the EventScanner still received new events.