Java tutorial
/* * 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.shared; import android.graphics.Canvas; import org.json.JSONException; import org.json.JSONObject; /** * Base class for different characters on the screen. */ public class Actor implements Comparable<Actor> { public static final float INFINITE_MASS = 0.0f; public static final String TYPE = "Actor"; public static final String TYPE_KEY = "type"; public static final String X_KEY = "x"; public static final String Y_KEY = "y"; public Vector2D positionBeforeFrame; // Assumes (0, 0) is upper-left corner of screen, with +y down and +x right. public Vector2D position; public Vector2D velocity; // Doesn't do anything yet (except for TextActors) public float scale = 1.0f; // The rotation of the actor in radians. Positive means clockwise, negative means anticlockwise. public float rotation = 0.0f; // Doesn't do anything yet (except for in tennis) public boolean hidden = false; // Specify z-index so that actors can be sorted before drawing. Higher is in front, lower in back. public int zIndex = 0; // 0: transparent, 1: opaque. public float alpha = 1; // Bounciness. public float restitution = 1.0f; public float inverseMass = INFINITE_MASS; public Actor() { this(Vector2D.get(0, 0), Vector2D.get(0, 0)); } public Actor(Vector2D position, Vector2D velocity) { this.position = position; this.positionBeforeFrame = Vector2D.get(position); this.velocity = velocity; } public void update(float deltaMs) { positionBeforeFrame.set(this.position); float deltaSeconds = deltaMs / 1000.0f; this.position.x += velocity.x * deltaSeconds; this.position.y += velocity.y * deltaSeconds; } public void draw(Canvas canvas) { // Nothing to do for base class implementation. } @Override public int compareTo(Actor another) { int zDiff = zIndex - another.zIndex; if (zDiff != 0) { return zDiff; } else { // As a fallback, compare the y positions. Obstacles with smaller y values (i.e., higher on // the screen) should come first. float positionDiff = position.y - another.position.y; if (positionDiff > 0) { return 1; } else if (positionDiff < 0) { return -1; } else { return 0; } } } public JSONObject toJSON() throws JSONException { return null; } public String getType() { return TYPE; } }