Android自定义surfaceView显示多张图片

我自定义了一个surfaceview，我在上面绘制多张图片，让它能够上下方滚显示图片，但是onMeasure（）方法在重写的时候遇到了问题，不知道如何设置它的高度，

public class MySurfaceView extends SurfaceView implements Callback{      private SurfaceHolder sfh;   private Paint paint;   public MySurfaceView(Context context) {    super(context);    init(context);   }           private void init(Context context) {    sfh=this.getHolder();    sfh.addCallback(this);    paint=new Paint();    paint.setColor(Color.WHITE);       }         public MySurfaceView(Context context, AttributeSet attrs, int defStyle) {    super(context,attrs,defStyle);    init(context);   }         public MySurfaceView(Context context, AttributeSet attrs) {    super(context,attrs);    init(context);     }         @Override   public void surfaceChanged(SurfaceHolder holder, int format, int width,int height) {       }     @Override   public void surfaceCreated(SurfaceHolder holder) {    myDraw();   }     private void myDraw() {    Canvas canvas=sfh.lockCanvas();    canvas.drawRect(0, 0, this.getWidth(), this.getHeight(), new Paint());    Bitmap bmp=readBitmap(getResources(), R.drawable.pic0);    Matrix matrix=new Matrix();        matrix.setScale(0.15f, 0.15f);    matrix.postTranslate(100, 0);    canvas.drawBitmap(bmp, matrix, paint);        matrix.postTranslate(0, 450);    bmp=readBitmap(getResources(), R.drawable.pic2);    canvas.drawBitmap(bmp, matrix, paint);        matrix.postTranslate(0, 500);    bmp=readBitmap(getResources(), R.drawable.pic5);    canvas.drawBitmap(bmp, matrix, paint);        matrix.postTranslate(0, 550);    bmp=readBitmap(getResources(), R.drawable.pic7);    canvas.drawBitmap(bmp, matrix, paint);        sfh.unlockCanvasAndPost(canvas);    if(bmp!=null)    bmp.recycle();   }     @Override   public void surfaceDestroyed(SurfaceHolder holder) {       }     @Override   public boolean onTouchEvent(MotionEvent event) {    return super.onTouchEvent(event);   }            @Override   protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {    // TODO Auto-generated method stub    super.onMeasure(widthMeasureSpec, heightMeasureSpec);        setMeasuredDimension(800, 2000);//2:5   2000 5000   1600 4000  2:5   }            public static Bitmap readBitmap(Resources r, int resId) {   BitmapFactory.Options opt = new BitmapFactory.Options();   opt.inPreferredConfig = Bitmap.Config.RGB_565;   opt.inPurgeable = true;   opt.inInputShareable = true;   InputStream is = r.openRawResource(resId);   return BitmapFactory.decodeStream(is, null, opt);      }    }