lunarview.java

android 例子中的LunarLander。很有代表意义

/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * 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.example.android.lunarlander;

import android.content.Context;
import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.RectF;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.AttributeSet;
import android.view.KeyEvent;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;
import android.widget.TextView;


/**
 * View that draws, takes keystrokes, etc. for a simple LunarLander game.
 * 
 * Has a mode which RUNNING, PAUSED, etc. Has a x, y, dx, dy, ... capturing the
 * current ship physics. All x/y etc. are measured with (0,0) at the lower left.
 * updatePhysics() advances the physics based on realtime. draw() renders the
 * ship, and does an invalidate() to prompt another draw() as soon as possible
 * by the system.
 */
class LunarView extends SurfaceView implements SurfaceHolder.Callback {
    class LunarThread extends Thread {
        /*
         * Difficulty setting constants
         */
        public static final int DIFFICULTY_EASY = 0;
        public static final int DIFFICULTY_HARD = 1;
        public static final int DIFFICULTY_MEDIUM = 2;
        /*
         * Physics constants
         */
        public static final int PHYS_DOWN_ACCEL_SEC = 35;
        public static final int PHYS_FIRE_ACCEL_SEC = 80;
        public static final int PHYS_FUEL_INIT = 60;
        public static final int PHYS_FUEL_MAX = 100;
        public static final int PHYS_FUEL_SEC = 10;
        public static final int PHYS_SLEW_SEC = 120; // degrees/second rotate
        public static final int PHYS_SPEED_HYPERSPACE = 180;
        public static final int PHYS_SPEED_INIT = 30;
        public static final int PHYS_SPEED_MAX = 120;
        /*
         * State-tracking constants
         */
        public static final int STATE_LOSE = 1;
        public static final int STATE_PAUSE = 2;
        public static final int STATE_READY = 3;
        public static final int STATE_RUNNING = 4;
        public static final int STATE_WIN = 5;

        /*
         * Goal condition constants
         */
        public static final int TARGET_ANGLE = 18; // > this angle means crash
        public static final int TARGET_BOTTOM_PADDING = 17; // px below gear
        public static final int TARGET_PAD_HEIGHT = 8; // how high above ground
        public static final int TARGET_SPEED = 28; // > this speed means crash
        public static final double TARGET_WIDTH = 1.6; // width of target
        /*
         * UI constants (i.e. the speed & fuel bars)
         */
        public static final int UI_BAR = 100; // width of the bar(s)
        public static final int UI_BAR_HEIGHT = 10; // height of the bar(s)
        private static final String KEY_DIFFICULTY = "mDifficulty";
        private static final String KEY_DX = "mDX";

        private static final String KEY_DY = "mDY";
        private static final String KEY_FUEL = "mFuel";
        private static final String KEY_GOAL_ANGLE = "mGoalAngle";
        private static final String KEY_GOAL_SPEED = "mGoalSpeed";
        private static final String KEY_GOAL_WIDTH = "mGoalWidth";

        private static final String KEY_GOAL_X = "mGoalX";
        private static final String KEY_HEADING = "mHeading";
        private static final String KEY_LANDER_HEIGHT = "mLanderHeight";
        private static final String KEY_LANDER_WIDTH = "mLanderWidth";
        private static final String KEY_WINS = "mWinsInARow";

        private static final String KEY_X = "mX";
        private static final String KEY_Y = "mY";

        /*
         * Member (state) fields
         */
        /** The drawable to use as the background of the animation canvas */
        private Bitmap mBackgroundImage;

        /**
         * Current height of the surface/canvas.
         * 
         * @see #setSurfaceSize
         */
        private int mCanvasHeight = 1;

        /**
         * Current width of the surface/canvas.
         * 
         * @see #setSurfaceSize
         */
        private int mCanvasWidth = 1;

        /** What to draw for the Lander when it has crashed */
        private Drawable mCrashedImage;

        /**
         * Current difficulty -- amount of fuel, allowed angle, etc. Default is
         * MEDIUM.
         */
        private int mDifficulty;

        /** Velocity dx. */
        private double mDX;

        /** Velocity dy. */
        private double mDY;

        /** Is the engine burning? */
        private boolean mEngineFiring;

        /** What to draw for the Lander when the engine is firing */
        private Drawable mFiringImage;

        /** Fuel remaining */
        private double mFuel;

        /** Allowed angle. */
        private int mGoalAngle;

        /** Allowed speed. */
        private int mGoalSpeed;

        /** Width of the landing pad. */
        private int mGoalWidth;

        /** X of the landing pad. */
        private int mGoalX;

        /** Message handler used by thread to interact with TextView */
        private Handler mHandler;

        /**
         * Lander heading in degrees, with 0 up, 90 right. Kept in the range
         * 0..360.
         */
        private double mHeading;

        /** Pixel height of lander image. */
        private int mLanderHeight;

        /** What to draw for the Lander in its normal state */
        private Drawable mLanderImage;

        /** Pixel width of lander image. */
        private int mLanderWidth;

        /** Used to figure out elapsed time between frames */
        private long mLastTime;

        /** Paint to draw the lines on screen. */
        private Paint mLinePaint;

        /** "Bad" speed-too-high variant of the line color. */
        private Paint mLinePaintBad;

        /** The state of the game. One of READY, RUNNING, PAUSE, LOSE, or WIN */
        private int mMode;

        /** Currently rotating, -1 left, 0 none, 1 right. */
        private int mRotating;

        /** Indicate whether the surface has been created & is ready to draw */
        private boolean mRun = false;

        /** Scratch rect object. */
        private RectF mScratchRect;

        /** Handle to the surface manager object we interact with */
        private SurfaceHolder mSurfaceHolder;

        /** Number of wins in a row. */
        private int mWinsInARow;

        /** X of lander center. */
        private double mX;

        /** Y of lander center. */
        private double mY;

        public LunarThread(SurfaceHolder surfaceHolder, Context context,
                Handler handler) {
            // get handles to some important objects
            mSurfaceHolder = surfaceHolder;
            mHandler = handler;
            mContext = context;

            Resources res = context.getResources();
            // cache handles to our key sprites & other drawables
            mLanderImage = context.getResources().getDrawable(
                    R.drawable.lander_plain);
            mFiringImage = context.getResources().getDrawable(
                    R.drawable.lander_firing);
            mCrashedImage = context.getResources().getDrawable(
                    R.drawable.lander_crashed);

            // load background image as a Bitmap instead of a Drawable b/c
            // we don't need to transform it and it's faster to draw this way
            mBackgroundImage = BitmapFactory.decodeResource(res,
                    R.drawable.earthrise);

            // Use the regular lander image as the model size for all sprites
            mLanderWidth = mLanderImage.getIntrinsicWidth();
            mLanderHeight = mLanderImage.getIntrinsicHeight();

            // Initialize paints for speedometer
            mLinePaint = new Paint();
            mLinePaint.setAntiAlias(true);
            mLinePaint.setARGB(255, 0, 255, 0);

            mLinePaintBad = new Paint();
            mLinePaintBad.setAntiAlias(true);
            mLinePaintBad.setARGB(255, 120, 180, 0);

            mScratchRect = new RectF(0, 0, 0, 0);

            mWinsInARow = 0;
            mDifficulty = DIFFICULTY_MEDIUM;

            // initial show-up of lander (not yet playing)
            mX = mLanderWidth;
            mY = mLanderHeight * 2;
            mFuel = PHYS_FUEL_INIT;
            mDX = 0;
            mDY = 0;
            mHeading = 0;
            mEngineFiring = true;
        }

        /**
         * Starts the game, setting parameters for the current difficulty.
         */
        public void doStart() {
            synchronized (mSurfaceHolder) {
                // First set the game for Medium difficulty
                mFuel = PHYS_FUEL_INIT;
                mEngineFiring = false;
                mGoalWidth = (int) (mLanderWidth * TARGET_WIDTH);
                mGoalSpeed = TARGET_SPEED;
                mGoalAngle = TARGET_ANGLE;
                int speedInit = PHYS_SPEED_INIT;

                // Adjust difficulty params for EASY/HARD
                if (mDifficulty == DIFFICULTY_EASY) {
                    mFuel = mFuel * 3 / 2;
                    mGoalWidth = mGoalWidth * 4 / 3;
                    mGoalSpeed = mGoalSpeed * 3 / 2;
                    mGoalAngle = mGoalAngle * 4 / 3;
                    speedInit = speedInit * 3 / 4;
                } else if (mDifficulty == DIFFICULTY_HARD) {
                    mFuel = mFuel * 7 / 8;
                    mGoalWidth = mGoalWidth * 3 / 4;
                    mGoalSpeed = mGoalSpeed * 7 / 8;
                    speedInit = speedInit * 4 / 3;
                }

                // pick a convenient initial location for the lander sprite
                mX = mCanvasWidth / 2;
                mY = mCanvasHeight - mLanderHeight / 2;

                // start with a little random motion
                mDY = Math.random() * -speedInit;
                mDX = Math.random() * 2 * speedInit - speedInit;