Ellipse Bounce using IntersectsWith

Question

I have a application where is ball (ellipse) and 4 rectangles (each for edge of window). I try to write a app where ball is moving and bouncing from the edges. I don't know how to make a method where ball changes a direction when collision is true.

XAML:

<Window x:Class="naszybkodlatestu.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="MainWindow" Height="320" Width="640">
<Canvas>
    <Rectangle Name="boardTop"
               Height="2"
               Fill="Black"
               Width="609" Canvas.Left="7" Canvas.Top="10"/>
    <Rectangle Name="boardLeft"
               Height="270"
               Fill="Black"
               Width="2" Canvas.Left="614" Canvas.Top="10"/>
    <Rectangle Name="boardRight"
               Height="269"
               Fill="Black"
               Width="2" Canvas.Left="7" Canvas.Top="12"/>
    <Rectangle Name="boardBot"
               Height="2"
               Fill="Black"
               Width="609" Canvas.Left="7" Canvas.Top="278" />
    <Ellipse Name="ball"
             Width="15"
             Height="15"
             Fill="Red" 
             Canvas.Left="303" 
             Canvas.Top="107"/>
</Canvas>
</Window>

C#:

DispatcherTimer dTimer;
private void InitTimer()
{
    dTimer = new DispatcherTimer();
    dTimer.Tick += new EventHandler(TickdTimer);
    dTimer.Interval = new TimeSpan(0, 0, 0, 0, 1);
    dTimer.Start();
}
public MainWindow()
{
    InitializeComponent();
    InitTimer();
    InitMove();

}

private bool isMovingUp = false;
private bool isMovingDown = false;
private bool isMovingLeft = true;
private bool isMovingRight = false;

private double ballDirectionX = 0;
private double ballDirectionY = 0;

private double ballSpeed = 1;

private bool CollisionDetection()
{
    if (CheckCollision(ball, boardBot) || CheckCollision(ball, boardRight) ||
        CheckCollision(ball, boardTop) || CheckCollision(ball, boardLeft))

    {
        return true;
    }
    else return false;
}

public static bool CheckCollision(FrameworkElement a, FrameworkElement b)
{
    Rect rect1 = new Rect((double)a.GetValue(Canvas.LeftProperty), (double)a.GetValue(Canvas.TopProperty), a.Width, a.Height);
    Rect rect2 = new Rect((double)b.GetValue(Canvas.LeftProperty), (double)b.GetValue(Canvas.TopProperty), b.Width, b.Height);

    if (rect1.IntersectsWith(rect2))
    {
        return true;
    }
        else return false;
}

private void InitMove()
{

    if (isMovingDown)
    {
        ballDirectionY += ballSpeed;
    }
    if (isMovingUp)
    {
        ballDirectionY -= ballSpeed;
    }
    if (isMovingLeft)
    {
        ballDirectionX -= ballSpeed;
    }
    if (isMovingRight)
    {
        ballDirectionX += ballSpeed;
    }
    ball.SetValue(Canvas.TopProperty, ballDirectionY);
    ball.SetValue(Canvas.LeftProperty, ballDirectionX);
}

So i tried smth like that in InitMove(). It's just a test code to show you what is a problem.

private void InitMove()
{
    .......
    if (CollisionDetection())
    {
        if (isMovingLeft)
        {
            isMovingLeft = false;
            isMovingRight = true;
        }
    }

So ball changed direction from left to right. Ok for now.

Problem starts now when i want to put next "if".

private void InitMove()
{
    .......
    if (CollisionDetection())
    {
        if (isMovingLeft)
        {
            isMovingLeft = false;
            isMovingRight = true;
        }
        if (isMovingRight)
        {
            isMovingRight = false;
            isMovingLeft = true;
        }
    }

Now ball is passing by edge of rectangle and there is no bounce. So here is my problem.

How to make it right?

//EDIT

When i added else

if (isMovingLeft)
{
    isMovingLeft = false;
    isMovingRight = true;
}
else if (isMovingRight)
{
    isMovingRight = false;
    isMovingLeft = true;
}

ball just stopped at edge of a window.

//EDIT2

ok so i think i know how to do this thx to you

if (isMovingLeft)
{
    isMovingLeft = false;
    isMovingRight = true;
    ballDirectionX += 2;
}
else if (isMovingRight)
{
    isMovingRight = false;
    isMovingLeft = true;
    ballDirectionX -= 2;
}

So i added some move to push this ball out of wall collision. I dont see another way for now.

Answer 1

Your two if statements are cancelling each other out when the ball is moving left. First you check if it is moving left, and set it to moving right. Then the next if statement is immediately evaluated, changing it back to moving to the left again. This is happening every time the code runs.

You need to change the second if statement to be an else if, so it won't do both in the same frame. Also the bounces will probably look a little weird unless you push them back out of the wall by the same amount that they went into it, but that is another issue.

Answer 2

You should add a else statement :

    if (isMovingLeft)
    {
        isMovingLeft = false;
        isMovingRight = true;
    }
    else if (isMovingRight)
    {
        isMovingRight = false;
        isMovingLeft = true;
    }