如何用surfaceview绘制正弦波

以下是一个用SurfaceView绘制正弦波的例子：

1. 创建一个继承自SurfaceView的类，重写它的surfaceCreated、surfaceChanged和surfaceDestroyed方法。

public class SinWaveView extends SurfaceView implements SurfaceHolder.Callback {
    private SurfaceHolder mSurfaceHolder;
    private DrawThread mDrawThread;

    public SinWaveView(Context context, AttributeSet attrs) {
        super(context, attrs);
        mSurfaceHolder = getHolder();
        mSurfaceHolder.addCallback(this);
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        mDrawThread = new DrawThread(holder);
        mDrawThread.start();
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {

    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        mDrawThread.exit();
    }

    private class DrawThread extends Thread {
        private SurfaceHolder mHolder;
        private boolean mRunning = true;

        public DrawThread(SurfaceHolder holder) {
            mHolder = holder;
        }

        @Override
        public void run() {
            while (mRunning) {
                Canvas canvas = null;
                try {
                    canvas = mHolder.lockCanvas();
                    drawSinWave(canvas);
                } finally {
                    if (canvas != null) {
                        mHolder.unlockCanvasAndPost(canvas);
                    }
                }
                try {
                    Thread.sleep(10);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }

        public void exit() {
            mRunning = false;
        }
    }

    private void drawSinWave(Canvas canvas) {
        int width = getWidth();
        int height = getHeight();
        Paint paint = new Paint();
        paint.setColor(Color.BLUE);
        paint.setStrokeWidth(5);
        paint.setStyle(Paint.Style.STROKE);

        Path path = new Path();
        float y;
        float centerY = height / 2;
        for (int x = 0; x < width; x++) {
            y = (float) (Math.sin(Math.toRadians(x * 3)) * 50 + centerY);
            if (x == 0) {
                path.moveTo(0, y);
            } else {
                path.lineTo(x, y);
            }
        }
        canvas.drawPath(path, paint);
    }
}

2. 在surfaceCreated方法中启动一个DrawThread线程，用于不断地绘制正弦波。

3. 在DrawThread线程中使用SurfaceHolder.lockCanvas获取Canvas对象，并在Canvas上调用自定义的drawSinWave方法绘制正弦波。

4. parseSinWave方法利用Path对象和Math.sin函数绘制正弦波曲线，其中Math.sin的参数为角度。