【Android】Android SurfaceView使用详解

来源：互联网发布：大数据工程师加班吗编辑：程序博客网时间：2024/06/02 10:01

http://codingnow.cn/android/603.html

1. SurfaceView的定义
前面已经介绍过View了，下面来简单介绍一下SurfaceView，参考SDK文档和网络资料：SurfaceView是View的子类，它内嵌了一个专门用于绘制的Surface，你可以控制这个Surface的格式和尺寸，Surfaceview控制这个Surface的绘制位置。surface是纵深排序(Z-ordered)的，说明它总在自己所在窗口的后面。SurfaceView提供了一个可见区域，只有在这个可见区域内的surface内容才可见。surface的排版显示受到视图层级关系的影响，它的兄弟视图结点会在顶端显示。这意味者 surface的内容会被它的兄弟视图遮挡，这一特性可以用来放置遮盖物(overlays)(例如，文本和按钮等控件)。注意，如果surface上面有透明控件，那么每次surface变化都会引起框架重新计算它和顶层控件的透明效果，这会影响性能。
SurfaceView默认使用双缓冲技术的，它支持在子线程中绘制图像，这样就不会阻塞主线程了，所以它更适合于游戏的开发。

2. SurfaceView的使用
首先继承SurfaceView，并实现SurfaceHolder.Callback接口，实现它的三个方法：surfaceCreated，surfaceChanged，surfaceDestroyed。
surfaceCreated(SurfaceHolder holder)：surface创建的时候调用，一般在该方法中启动绘图的线程。
surfaceChanged(SurfaceHolder holder, int format, int width,int height)：surface尺寸发生改变的时候调用，如横竖屏切换。
surfaceDestroyed(SurfaceHolder holder) ：surface被销毁的时候调用，如退出游戏画面，一般在该方法中停止绘图线程。
还需要获得SurfaceHolder，并添加回调函数，这样这三个方法才会执行。

3. SurfaceView实战
下面通过一个小demo来学习SurfaceView在实际项目中的使用，绘制一个精灵，该精灵有四个方向的行走动画，让精灵沿着屏幕四周不停的行走。游戏中精灵素材和最终实现的效果图:

首先创建核心类GameView.java，源码如下：

import android.content.Context;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.graphics.Canvas;import android.graphics.Color;import android.view.SurfaceHolder;import android.view.SurfaceView;import java.io.InputStream;public class GameSurfaceView extends SurfaceView implements SurfaceHolder.Callback {    //屏幕宽高    public static int SCREEN_WIDTH;    public static int SCREEN_HEIGHT;    private Context mContext;    private SurfaceHolder mHolder;    //最大帧数 (1000 / 30)    private static final int DRAW_INTERVAL = 30;    private DrawThread mDrawThread;    private FrameAnimation []spriteAnimations;    private Sprite mSprite;    private int spriteWidth = 0;    private int spriteHeight = 0;    private float spriteSpeed = (float)((500  * SCREEN_WIDTH / 480) * 0.001);    private int row = 4;    private int col = 4;    public GameSurfaceView(Context context) {        super(context);        this.mContext = context;        mHolder = this.getHolder();        mHolder.addCallback(this);        initResources();        mSprite = new Sprite(spriteAnimations,0,0,spriteWidth,spriteHeight,spriteSpeed);    }    private void initResources() {        Bitmap[][] spriteImgs = generateBitmapArray(mContext, R.drawable.pic1, row, col);        spriteAnimations = new FrameAnimation[row];        for(int i = 0; i < row; i ++) {            Bitmap []spriteImg = spriteImgs[i];            FrameAnimation spriteAnimation = new FrameAnimation(spriteImg,new int[]{150,150,150,150},true);            spriteAnimations[i] = spriteAnimation;        }    }    public Bitmap decodeBitmapFromRes(Context context, int resourseId) {        BitmapFactory.Options opt = new BitmapFactory.Options();        opt.inPreferredConfig = Bitmap.Config.RGB_565;        opt.inPurgeable = true;        opt.inInputShareable = true;        InputStream is = context.getResources().openRawResource(resourseId);        return BitmapFactory.decodeStream(is, null, opt);    }    public Bitmap createBitmap(Context context, Bitmap source, int row,                               int col, int rowTotal, int colTotal) {        Bitmap bitmap = Bitmap.createBitmap(source,                (col - 1) * source.getWidth() / colTotal,                (row - 1) * source.getHeight() / rowTotal, source.getWidth()                        / colTotal, source.getHeight() / rowTotal);        return bitmap;    }    public Bitmap[][] generateBitmapArray(Context context, int resourseId,                                          int row, int col) {        Bitmap bitmaps[][] = new Bitmap[row][col];        Bitmap source = decodeBitmapFromRes(context, resourseId);        this.spriteWidth = source.getWidth() / col;        this.spriteHeight = source.getHeight() / row;        for (int i = 1; i <= row; i++) {            for (int j = 1; j <= col; j++) {                bitmaps[i - 1][j - 1] = createBitmap(context, source, i, j,                        row, col);            }        }        if (source != null && !source.isRecycled()) {            source.recycle();            source = null;        }        return bitmaps;    }    public void surfaceChanged(SurfaceHolder holder, int format, int width,                               int height) {    }    public void surfaceCreated(SurfaceHolder holder) {        if(null == mDrawThread) {            mDrawThread = new DrawThread();            mDrawThread.start();        }    }    public void surfaceDestroyed(SurfaceHolder holder) {        if(null != mDrawThread) {            mDrawThread.stopThread();        }    }    private class DrawThread extends Thread {        public boolean isRunning = false;        public DrawThread() {            isRunning = true;        }        public void stopThread() {            isRunning = false;            boolean workIsNotFinish = true;            while (workIsNotFinish) {                try {                    this.join();// 保证run方法执行完毕                } catch (InterruptedException e) {                    // TODO Auto-generated catch block                    e.printStackTrace();                }                workIsNotFinish = false;            }        }        public void run() {            long deltaTime = 0;            long tickTime = 0;            tickTime = System.currentTimeMillis();            while (isRunning) {                Canvas canvas = null;                try {                    synchronized (mHolder) {                        canvas = mHolder.lockCanvas();                        //设置方向                        mSprite.setDirection();                        //更新精灵位置                        mSprite.updatePosition(deltaTime);                        drawSprite(canvas);                    }                } catch (Exception e) {                    e.printStackTrace();                } finally {                    if (null != mHolder) {                        mHolder.unlockCanvasAndPost(canvas);                    }                }                deltaTime = System.currentTimeMillis() - tickTime;                if(deltaTime < DRAW_INTERVAL) {                    try {                        Thread.sleep(DRAW_INTERVAL - deltaTime);                    } catch (InterruptedException e) {                        e.printStackTrace();                    }                }                tickTime = System.currentTimeMillis();            }        }    }    private void drawSprite(Canvas canvas) {        //清屏操作        canvas.drawColor(Color.BLACK);        mSprite.draw(canvas);    }}

GameView.java中包含了一个绘图线程DrawThread，在线程的run方法中锁定Canvas、绘制精灵、更新精灵位置、释放Canvas等操作。因为精灵素材是一张大图，所以这里进行了裁剪生成一个二维数组。使用这个二维数组初始化了精灵四个方向的动画，下面看Sprite.java的源码。

import android.graphics.Bitmap;import android.graphics.Canvas;public class Sprite {    public static final int DOWN = 0;    public static final int LEFT = 1;    public static final int RIGHT = 2;    public static final int UP = 3;    public float x;    public float y;    public int width;    public int height;    //精灵行走速度    public double speed;    //精灵当前行走方向    public int direction;    //精灵四个方向的动画    public FrameAnimation[] frameAnimations;    public Sprite(FrameAnimation[] frameAnimations, int positionX,                  int positionY, int width, int height, float speed) {        this.frameAnimations = frameAnimations;        this.x = positionX;        this.y = positionY;        this.width = width;        this.height = height;        this.speed = speed;    }    public void updatePosition(long deltaTime) {        switch (direction) {            case LEFT:                //让物体的移动速度不受机器性能的影响,每帧精灵需要移动的距离为：移动速度*时间间隔                this.x = this.x - (float) (this.speed * deltaTime);                break;            case DOWN:                this.y = this.y + (float) (this.speed * deltaTime);                break;            case RIGHT:                this.x = this.x + (float) (this.speed * deltaTime);                break;            case UP:                this.y = this.y - (float) (this.speed * deltaTime);                break;        }    }    /**     *      * 根据精灵的当前位置判断是否改变行走方向     *           */    public void setDirection() {        if (this.x <= 0 && (this.y + this.height) < GameSurfaceView.SCREEN_HEIGHT) {            if (this.x < 0)                this.x = 0;            this.direction = Sprite.DOWN;        } else if ((this.y + this.height) >= GameSurfaceView.SCREEN_HEIGHT && (this.x + this.width) < GameSurfaceView.SCREEN_WIDTH) {            if ((this.y + this.height) > GameSurfaceView.SCREEN_HEIGHT)                this.y = GameSurfaceView.SCREEN_HEIGHT - this.height;            this.direction = Sprite.RIGHT;        } else if ((this.x + this.width) >= GameSurfaceView.SCREEN_WIDTH && this.y > 0) {            if ((this.x + this.width) > GameSurfaceView.SCREEN_WIDTH)                this.x = GameSurfaceView.SCREEN_WIDTH - this.width;            this.direction = Sprite.UP;        } else {            if (this.y < 0)                this.y = 0;            this.direction = Sprite.LEFT;        }    }    public void draw(Canvas canvas) {        FrameAnimation frameAnimation = frameAnimations[this.direction];        Bitmap bitmap = frameAnimation.nextFrame();        if (null != bitmap) {            canvas.drawBitmap(bitmap, x, y, null);        }    }}

精灵类主要是根据当前位置判断行走的方向，然后根据行走的方向更新精灵的位置，再绘制自身的动画。由于精灵的动画是一帧一帧的播放图片，所以这里封装了FrameAnimation.java，源码如下：

import android.graphics.Bitmap;public class FrameAnimation {    /**     * 动画显示的需要的资源     */    private Bitmap[] bitmaps;    /**     * 动画每帧显示的时间     */    private int[] duration;    /**     * 动画上一帧显示的时间     */    protected Long lastBitmapTime;    /**     * 动画显示的索引值，防止数组越界     */    protected int step;    /**     * 动画是否重复播放     */    protected boolean repeat;    /**     * 动画重复播放的次数     */    protected int repeatCount;    /**     *     * @param bitmap:显示的图片<br/>     *     * @param duration:图片显示的时间<br/>     *     * @param repeat:是否重复动画过程<br/>     *          */    public FrameAnimation(Bitmap[] bitmaps, int duration[], boolean repeat) {        this.bitmaps = bitmaps;        this.duration = duration;        this.repeat = repeat;        lastBitmapTime = null;        step = 0;    }    public Bitmap nextFrame() {// 判断step是否越界        if (step >= bitmaps.length) {//如果不无限循环            if (!repeat) {                return null;            } else {                lastBitmapTime = null;            }        }        if (null == lastBitmapTime) {// 第一次执行            lastBitmapTime = System.currentTimeMillis();            return bitmaps[step = 0];        }// 第X次执行        long nowTime = System.currentTimeMillis();        if (nowTime - lastBitmapTime <= duration[step]) {// 如果还在duration的时间段内,则继续返回当前Bitmap// 如果duration的值小于0,则表明永远不失效,一般用于背景            return bitmaps[step];        }        lastBitmapTime = nowTime;        return bitmaps[step++];// 返回下一Bitmap    }}

FrameAnimation根据每一帧的显示时间返回当前的图片帧，若没有超过指定的时间则继续返回当前帧，否则返回下一帧。
接下来需要做的是让Activty显示的View为我们之前创建的GameView，然后设置全屏显示。

        DisplayMetrics outMetrics = new DisplayMetrics();        this.getWindowManager().getDefaultDisplay().getMetrics(outMetrics);        GameSurfaceView.SCREEN_WIDTH = outMetrics.widthPixels;        GameSurfaceView.SCREEN_HEIGHT = outMetrics.heightPixels;        GameSurfaceView gameView = new GameSurfaceView(this);        setContentView(gameView);

现在运行Android工程，应该就可以看到一个手持宝剑的武士在沿着屏幕不停的走了。

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