com.google.android.apps.santatracker.doodles.tilt.StickyActor.java Source code

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Here is the source code for com.google.android.apps.santatracker.doodles.tilt.StickyActor.java

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/*
 * Copyright (C) 2016 Google Inc. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.google.android.apps.santatracker.doodles.tilt;

import android.graphics.Color;
import com.google.android.apps.santatracker.doodles.shared.Actor;
import com.google.android.apps.santatracker.doodles.shared.Vector2D;
import com.google.android.apps.santatracker.doodles.shared.physics.Polygon;
import org.json.JSONException;
import org.json.JSONObject;

/**
 * An actor which slows down the colliding actor upon entry.
 */
public class StickyActor extends CollisionActor {
    public static final String TYPE = "Sticky";
    // A "stickiness" factor, which is essentially friction, but doesn't take into account the tilt
    // of the device.
    private float stickiness = 2.0f;
    public boolean isEnabled = true;

    public StickyActor(Polygon collisionBody) {
        super(collisionBody);
        // cyan, yellow, semi-transparent green.
        collisionBody.setPaintColors(Color.CYAN, 0xffffff00, 0x6400ff00);
    }

    /**
     * Cause the other actor to be slowed down by this actor.
     */
    @Override
    public boolean resolveCollision(Actor other, float deltaMs) {
        if (!isEnabled || other.velocity.getLength() == 0 || !collisionBody.contains(other.position)) {
            // Don't bother resolving the collision if the other actor is either not moving, or if the
            // other actor is not colliding with this object.
            return false;
        }
        float deltaSeconds = deltaMs / 1000.0f;
        Vector2D acceleration = Vector2D.get(other.velocity).normalize();
        if (other.velocity.getLength() < 400) {
            acceleration.scale(0.01f * stickiness * Constants.GRAVITY);
        } else {
            acceleration.scale(stickiness * Constants.GRAVITY);
        }
        if (Math.signum(other.velocity.x - acceleration.x * deltaSeconds) != Math.signum(other.velocity.x)) {
            // Don't allow stickiness to accelerate the ball in the other direction.
            other.velocity.x = 0;
            other.velocity.y = 0;
        } else {
            other.velocity.x -= acceleration.x * deltaSeconds;
            other.velocity.y -= acceleration.y * deltaSeconds;
        }
        return false;
    }

    @Override
    public String getType() {
        return StickyActor.TYPE;
    }

    public static StickyActor fromJSON(JSONObject json) throws JSONException {
        return new StickyActor(Polygon.fromJSON(json.getJSONArray(POLYGON_KEY)));
    }
}