CocosCreatorTutorial/Rocker/RockerDemo2/assets/Script/rocker.js

cc.Class({
    extends: cc.Component,

    properties: {
        bg: cc.Node,
        rocker: cc.Node
    },

    // use this for initialization
    onLoad: function () {
        this.start = false;
        this.angle = -1;
        this.radian = -1;
        this.node.on("touchstart", this.mouseDown, this);
        this.node.on("touchmove", this.mouseMove, this);
        this.node.on('touchcancel', this.mouseEnd, this);
        this.node.on('touchend', this.mouseEnd, this);
    },

    // called every frame
    update: function (dt) {

    },

    mouseEnd() {
        this.rocker.setPosition(cc.v2(0, 0));
    },

    mouseDown: function (event) {
        // this.startPos = this.node.convertToNodeSpaceAR(event.getLocation());
    },

    mouseMove: function (event) {
        var pos = this.bg.convertToNodeSpaceAR(event.getLocation());
        if (this.getDistance(cc.p(0, 0), pos) <= 50) {
            this.rocker.setPosition(pos);
        } else {
            var radian = this.getRadian(pos);
            pos.y = Math.sin(radian) * 50;
            pos.x = Math.cos(radian) * 50;
            this.rocker.setPosition(pos);
        }
    },

    getDistance: function (pos1, pos2) {
        var x = (pos1.x - pos2.x);
        var y = (pos1.y - pos2.y);
        return Math.sqrt((x * x + y * y));
    },

    getRadian: function (point) {
        this.radian = Math.atan2(point.y, point.x);
        return this.radian;
    },

    getAngle: function (point) {
        this.angle = Math.atan2(point.y, point.x) * (180 / Math.PI);
        return this.angle;
    }
});