Drag an Image in XNA

I am working on an app in which images are flying on the Scree开发者_如何转开发n. I need to implement:

1. Hold onto any of the flying images on Tap
2. Drag the image to certain position of the user's choice by letting the user hold it.

Here is another easy way to do dragging. Just draw your image (Texture2d) with respect to a Rectangle instead of Vector2. Your image variables should look like this

Texture2d image;
Rectangle imageRect;

Draw your image with respect to "imageRect" in Draw() method.

spriteBatch.Draw(image,imageRect,Color.White);

Now in Update() method handle your image with single touch input.

//Move your image with your logic

TouchCollection touchLocations = TouchPanel.GetState();
foreach(TouchLocation touchLocation in touchLocations)
{
  Rectangle touchRect = new Rectangle 
    (touchLocation.Position.X,touchLocation.Position.Y,10,10);
  if(touchLocation.State == TouchLocationState.Moved
     && imageRect.Intersects(touchRect))
  {
   imageRect.X = touchRect.X;
   imageRect.Y = touchRect.Y;
  }
//you can bring more beauty by bringing centre point 
//of imageRect instead of initial point by adding width
//and height to X and Y respectively and divide it by 2

There's a drag-and-drag example in XNA here: http://geekswithblogs.net/mikebmcl/archive/2011/03/27/drag-and-drop-in-a-windows-xna-game.aspx

When you load your image in, you'll need a BoundingBox or Rectangle Object to control where it is.

So, in the XNA app on your phone, you should have a couple of objects declared for your texture.

Texture2D texture;
BoundingBox bBox;
Vector2 position;
bool selected;

Then after you load your image content, keep your bounding box updated with the position of your image.

bBox.Min = new Vector3(position, 1.0f);
bBox.Max = new Vector3(position.X + texture.Width, position.Y + texture.Height, 0f);

Then also in your update method, you should have a touch collection initialized to handle input from the screen, get the positions of the touch collection, loop through them and see if they intersect your boundingbox.

foreach (Vector2 pos in touchPositions)
{
   BoundingBox bb = new BoundingBox();
   bb.Min = new Vector3(pos, 1.0f);
   bb.Max = new Vector3(pos, 0f);

   if (bb.Intersects(bBox)
   {
       if (selected)
       {
           //do something
       }
       else
       {
           selected = true;
       }
   }
}

From there, you have whether your object is selected or not. Then just use the gestures events to determine what you want to do with your texture object.