Android SurfaceView使用详解（很好的实战例子）
一、 surfaceview 主要作用
（1）视频输出的屏幕。（这个用得比较多）
（2）绘制图像
二、注意事项
surfaceCreated有特定的生命周期，注意在callback中进行操作。（具体请看例子）
三、清屏操作(绘制图像)
public void clearDraw(SurfaceHolder holder,int color) {
Log.w("tan","clearDraw");
Canvas canvas = null;
try {
canvas = holder.lockCanvas(null);
canvas.drawColor(color);
}catch (Exception e) {
// TODO: handle exception
e.printStackTrace();
}finally {
if(canvas != null) {
holder.unlockCanvasAndPost(canvas);
}
}
}
------------------------------------------------- 正文 ----------------------------------
一、视频输出的屏幕
（1）设置surfaceview的参数
（2）在SurfaceCallback方法进行视频的播放控制。播放控制时，一般会进行播放器与surfaceview的绑定操作（如下）。注意这个getHolder。无论是surfaceview 还是TextureView都有这个holder。是视频输出的 关键。
mediaPlayer.setDisplay(surfaceView.getHolder());代码：
public class MainActivity extends Activity {
private EditText nameText;
private String path;
private MediaPlayer mediaPlayer;
private SurfaceView surfaceView;
private boolean pause;
private int position;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
mediaPlayer = new MediaPlayer();
nameText = (EditText) this.findViewById(R.id.filename);
surfaceView = (SurfaceView) this.findViewById(R.id.surfaceView);
//把输送给surfaceView的视频画面，直接显示到屏幕上,不要维持它自身的缓冲区
surfaceView.getHolder().setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
surfaceView.getHolder().setFixedSize(176, 144);
surfaceView.getHolder().setKeepScreenOn(true);
surfaceView.getHolder().addCallback(new SurfaceCallback());
}
private final class SurfaceCallback implements Callback{
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
}
public void surfaceCreated(SurfaceHolder holder) {
if(position>0 && path!=null){
play(position);
position = 0;
}
}
public void surfaceDestroyed(SurfaceHolder holder) {
if(mediaPlayer.isPlaying()){
position = mediaPlayer.getCurrentPosition();
mediaPlayer.stop();
}
}
}
@Override
protected void onDestroy() {
mediaPlayer.release();
mediaPlayer = null;
super.onDestroy();
}
public void mediaplay(View v){
switch (v.getId()) {
case R.id.playbutton:
String filename = nameText.getText().toString();
if(filename.startsWith("http")){
path = filename;
play(0);
}else{
File file = new File(Environment.getExternalStorageDirectory(), filename);
if(file.exists()){
path = file.getAbsolutePath();
play(0);
}else{
path = null;
Toast.makeText(this, R.string.filenoexsit, 1).show();
}
}
break;
case R.id.pausebutton:
if(mediaPlayer.isPlaying()){
mediaPlayer.pause();
pause = true;
}else{
if(pause){
mediaPlayer.start();
pause = false;
}
}
break;
case R.id.resetbutton:
if(mediaPlayer.isPlaying()){
mediaPlayer.seekTo(0);
}else{
if(path!=null){
play(0);
}
}
break;
case R.id.stopbutton:
if(mediaPlayer.isPlaying()){
mediaPlayer.stop();
}
break;
}
}
private void play(int position) {
try {
mediaPlayer.reset();
mediaPlayer.setDataSource(path);
mediaPlayer.setDisplay(surfaceView.getHolder());
mediaPlayer.prepare();//缓冲
mediaPlayer.setOnPreparedListener(new PrepareListener(position));
} catch (Exception e) {
e.printStackTrace();
}
}
private final class PrepareListener implements OnPreparedListener{
private int position;
public PrepareListener(int position) {
this.position = position;
}
public void onPrepared(MediaPlayer mp) {
mediaPlayer.start();//播放视频
if(position>0) mediaPlayer.seekTo(position);
}
}
}
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二、绘制图像
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：
public class GameView 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.sprite, 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。
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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：
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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。
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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。