how to pass rectenge from one event function to another?

Question

0.00/5 (No votes)

See more:

I want to to pass a rectangle from one function to a second function
For some reason the rectangel read to the event function as null
How can I do this?

C#

      private Point startpoint;
      private Rectangle rect;

      private void canvas1_MouseRightButtonDown(object sender, MouseButtonEventArgs e)
      {

          startpoint = Mouse.GetPosition(canvas1);

// the rectengle that i creat and i what to pass him to the canvas1_MouseMove Event function
          Rectangle rect = new Rectangle();
          rect.Stroke = Brushes.Black;
          rect.StrokeThickness = 1;


          canvas1.Children.Add(rect);



      }



      private void canvas1_MouseMove(object sender, MouseEventArgs e)
      {
         //to here i want to pass the rectangle
         // when i debug the code the rect value is null!
         // so i cant control his Properties


              rect.Width = 5;// her i got excsption
                             //"Object reference not set to an instance of an object."
              rect.Height = 6;





      }

Posted 14-Nov-13 4:01am

Member 10388286

Updated 14-Nov-13 4:40am

v6

Add a Solution

Comments

BillWoodruff 14-Nov-13 10:17am

I can't understand your question. You create a variable named in the scope of whatever (Class ?) and in both MouseRightButtonDown and MouseMove functions. That's three Rectangles named 'rect.

The TextBox you set text of doesn't make use of 'rect.

You need to rewrite your question.

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Mike Meinz · Accepted Answer · 2013-11-14T04:07:00

Solution 1

This is the simplest way to do it.

C#

        private Point startpoint;

// "rect" is declared at Class level so both canvas1_MouseRightButtonDown and canvas1_MouseMove can access
        private Rectangle rect; 
 
        private void canvas1_MouseRightButtonDown(object sender, MouseButtonEventArgs e)
        {
            startpoint = Mouse.GetPosition(canvas1);
 
            rect = new Rectangle();  // Changed declaration and assignment to just assignment
            rect.Stroke = Brushes.Black;
            rect.StrokeThickness = 1;
 
            canvas1.Children.Add(rect);
         }
 
        
 
        private void canvas1_MouseMove(object sender, MouseEventArgs e)
        {
        if (rect != null) // Check to be sure rect is OK. Mouse will move before right-click.
        {
                 rect.Width = 5;
                rect.Height = 6;
        }
                
        }

Posted 14-Nov-13 4:07am

Mike Meinz

Updated 14-Nov-13 5:21am

v10

Comments

[no name] 14-Nov-13 10:13am

i try the i got exption on

rect.Width = Math.Abs(w); //Object reference not set to an instance of an object.

Mike Meinz 14-Nov-13 10:20am

That means that canvas1_MouseMove was called and click == true was true before canvas1_MouseRightButtonDown was completed. What if you moved click = true; to the bottom of canvas1_MouseRightButtonDown?

And maybe add a check into canvas1_MouseMove that rect is not null to ensure that canvas1_MouseRightButtonDown was executed before canvas1_MouseMove.

See revised Solution 1.

[no name] 14-Nov-13 10:33am

Not related to the variable click
I just want to move the rectangle from one function to another

Mike Meinz 14-Nov-13 10:36am

The variable click is what you are using as a signal to indicate that the rect variable was instantiated. See revised Solution 1.

if (click == true && rect != null)

[no name] 14-Nov-13 10:42am

the variable click has nothing to do With this
i revised my question

Mike Meinz 14-Nov-13 10:50am

See my revised Solution 1.

You had declared rect in canvas1_MouseRightButtonDown. You only need to instantiate rect in canvas1_MouseRightButtonDown since you already declared it at the class level. Your code never instantiates the rect variable at the class level. My Solution 1 solves this.

I added the check for rect != null into canvas1_MouseMove. This ensures that the code in canvas1_MouseMove only runs after rect has been instantiated. canvas1_MouseMove is going to run as soon as you move your mouse a tiny bit inside canvas1 area. Therefore, you have to have a check to be sure that rect has been instantiated.

[no name] 14-Nov-13 10:58am

but it is allway null !! i want that it will pass to that function
that is my problem

Mike Meinz 14-Nov-13 11:01am

It is always null because you are declaring a new rect variable in canvas1_MouseRightButtonDown instead of using the rect variable already declared at the class level. See my Solution 1.

Use Visual Studio interactive debugger and set a breakpoint at assignment to rect in canvas1_MouseRightButtonDown. Then you can see when and if rect variable at the class level is getting instantiated.

Also, you must add if (rect != null) into canvas1_MouseMove because the mouse will move before the right-click. You have to use if (rect != null) to ensure that rect has been instantiated.