Dragging collisions

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I am pretty new to both CANVAS and Kineticjs but I feel what I am attemping should be much easier then I am making it out to be. Basically this is what I have so far:

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滥情空心

2020-12-22 08:20

Yes, since KineticJS doesn't have collision testing you must do your own.

Here is a collision test between any 2 kineticJS rectangles:

function theyAreColliding(rect1, rect2) {
  return !(rect2.getX() > rect1.getX()+rect1.getWidth() || 
           rect2.getX()+rect2.getWidth() < rect1.getX() || 
           rect2.getY() > rect1.getY()+rect1.getHeight() ||
           rect2.getY()+rect2.getHeight() < rect1.getY());
}

And here is how you would call the collision test between the box and obstacle:

if( theyAreColliding(box,obstacle){
      // obstacle is blocking box
      alert("You are being blocked!");
}

And here is how you would call the collision test between the box and the goal:

if( theyAreColliding(box,target){
      // box touched the goal
      alert("Goal!");
}

To stop the box from dragging right through the obstacle, you must give box a custom drag function like this:

dragBoundFunc: function(pos){
    if(theyAreColliding(box,obstacle){
        // box is touching obstacle
        // don't let box move down
        return({ x:pos.x, y:obstacle.getY()-1 });
    } else{
        // box is not touching obstacle
        // let it move ahead
        return({ x:pos.x, y:pos.y });
    }
}

You can see how this works in a demo at: http://www.html5canvastutorials.com/kineticjs/html5-canvas-drag-and-drop-bounds-tutorial-with-kineticjs/

[Edit: specify where each code goes]

I put the pieces together into a working snippet below. I did find one unfortunate thing. It’s possible for the user to drag the pink box fast enough to go right through the obstacle—KineticJS can’t react fast enough to stop a very fast drag.

Also--oops on me. I corrected some missing parentheses in the theyAreColliding function above.

The dragBoundFunc goes as an addition to the box constructor (see code below).

You can test if the user has a goal by testing in the box’s “dragmove” handler, like this:

  box.on('dragmove', function() {
    if (theyAreColliding(box, target)) {
        // box touched the goal
        alert("Goal!");
    }      
  });

Here is code and a Fiddle: http://jsfiddle.net/uCAys/

<!DOCTYPE HTML>
<html>
  <head>
    <style>
body {
    margin: 0px;
    padding: 20px;
}
canvas {
    border: 1px solid #777;
}
    </style>
  </head>
  <body>
    <div id="container"></div>
    <script src="http://www.html5canvastutorials.com/libraries/kinetic-v4.3.1-beta2.js"></script>
    <script>
        var stage = new Kinetic.Stage({
            container: 'container',
            width: 300,
            height: 300
        });
        var layer = new Kinetic.Layer();

        //Dragable Pink box
        var box = new Kinetic.Rect({
            x: 100,
            y: 50,
            width: 100,
            height: 50,
            fill: 'pink',
            stroke: 'black',
            strokeWidth: 2,
            draggable: true,
            // this causes box to be stopped if contacting obstacle
            dragBoundFunc: function(pos){
                if(theyAreColliding(box,obstacle)){
                    // box is touching obstacle
                    // don't let box move down
                    return({ 
                        x: pos.x, 
                        y: Math.min( obstacle.getY()-box.getHeight()-1, pos.y)
                    });
                } else{
                    // box is not touching obstacle
                    // let it move ahead
                    return({ x:pos.x, y:pos.y });
                }
            } 
        });

      box.on('dragmove', function() {
        if (theyAreColliding(box, target)) {
            // box touched the goal
            box.setX(100);
            box.setY(50);
            alert("Goal!");
        }      
      });

        // End goal blue box
        var target = new Kinetic.Rect({
            x: 100,
            y: 200,
            width: 100,
            height: 50,
            fill: 'blue',
            stroke: 'black',
            strokeWidth: 2
        });

        // Obstacle/blocker orange box
        var obstacle = new Kinetic.Rect({
            x: 125,
            y: 145,
            width: 50,
            height: 30,
            fill: 'orange',
            stroke: 'black',
            strokeWidth: 2
        });

        function theyAreColliding(rect1, rect2) {
            return !(rect2.getX() > rect1.getX() + rect1.getWidth() ||  //
                     rect2.getX() + rect2.getWidth() < rect1.getX() ||  // 
                     rect2.getY() > rect1.getY() + rect1.getHeight() ||   //
                     rect2.getY() + rect2.getHeight() < rect1.getY());  //
        }

        layer.add(box);
        layer.add(obstacle);
        layer.add(target);
        stage.add(layer);

    </script>
  </body>
</html>

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