CODEWITHSUNDEEP
javagraphicsevent-handling
imulsion
imulsion

Reputation: 9040

Java mouseDown Event object

When you use the method 

public boolean mouseDown(Event e, int x, int y)

in Java, what does the Event object do or what is it used for? I am trying to write a program that involves someone clicking on a rectangle created by

g.fillRect(horizontal position,vertical position,height,width);

I presume you use event handling to pick up the click on the rectangle with the mousedown method, but how can u do this? Please provide examples in your answers. I did my research on Google, and found nothing, even with really specific searches. Help greatly appreciated!

Upvotes: 2

Views: 10793

Answers (3)

Zac
Zac

Reputation: 2211

mouseDown is a mouse event. What you need to do is add an event listener to your program, so when the mouse is clicked an event handler calls a method. In this method you want to see if the x,y position of the mouse is within the rectangle.

You will need to implement MouseListener "implements MouseListener" 

// import an extra class for the MouseListener 
import java.awt.event.*;

public class YourClassName extends Applet implements MouseListener 
{
     int x = horizontal position;
     int y = vertical position;
     g.fillRect(x,y,width,height);
     addMouseListener(this); 

     // These methods always have to present when you implement MouseListener
     public void mouseClicked (MouseEvent mouseEvent) {} 
     public void mouseEntered (MouseEvent mouseEvent) {} 
     public void mousePressed (MouseEvent mouseEvent) {} 
     public void mouseReleased (MouseEvent mouseEvent) {}  
     public void mouseExited (MouseEvent mouseEvent) {}  

     public void mouseClicked (MouseEvent mouseEvent) {
     mouseX = mouseEvent.getX();
     mouseY = mouseEvent.getY();
     if(mouseX > x && mouseY > y && mouseX < x+width && mouseY < y+height){
         //
         // do whatever 
         //
     }
}

for more... http://docs.oracle.com/javase/6/docs/api/java/awt/event/MouseListener.html

Upvotes: 3

Kumar Vivek Mitra
Kumar Vivek Mitra

Reputation: 33534

As you have asked this

in Java, what does the Event object do or what is it used for?

- First of all there are Event Source, when any action take place on the Event Source, an Event Object is thrown to the call back method.

- Call Back method is the method inside the Listener (Interface) which is needed to be implemented by the Class that implements this Listener.

- The statements inside this call back method will dictate whats needed to be done, when the action is done on the Event Source.

Eg:

Assume

  Event Source - Button
  When Clicked - Event object is thrown at the call back method
  Call back method - actionPerformed(ActionEvent e) inside ActionListener.

- In your example when the mouse button goes down, the x and y co-ordinate gets noted. Then the event object it thrown at its call back method, which needs to be handled by the class that implements this Listener.

- Its better to use mousePressed method of MouseListener Interface.

See this link:

http://docs.oracle.com/javase/6/docs/api/java/awt/event/MouseListener.html#mousePressed%28java.awt.event.MouseEvent%29

Upvotes: 0

Suraj Chandran
Suraj Chandran

Reputation: 24791

The Event object contains information like the

  1. x and y coordinates of the event,
  2. The target component on which the event happened
  3. when the even happened

It provides lot of other information as well.
Note: The method is deprecated in favour of processMouseEvent().

Upvotes: 2

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