surfaceview缩放

要在SurfaceView上实现缩放，可以考虑以下两种方法：

1. 使用Matrix进行缩放

可以在SurfaceView的回调函数`surfaceChanged()`中获取SurfaceView的宽高，然后使用Matrix进行缩放操作，将缩放后的图像绘制到SurfaceView上。

示例代码：

public class MySurfaceView extends SurfaceView implements SurfaceHolder.Callback {
    private SurfaceHolder mHolder;
    private Paint mPaint;
    private Bitmap mBitmap;
    private Matrix mMatrix;
    private float mScaleFactor = 1.0f;

    public MySurfaceView(Context context) {
        super(context);
        init();
    }

    public MySurfaceView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    private void init() {
        mHolder = getHolder();
        mHolder.addCallback(this);
        mPaint = new Paint();
        mMatrix = new Matrix();
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
        mBitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        // 开启线程绘制图像
        new Thread(new Runnable() {
            @Override
            public void run() {
                while (true) {
                    draw();
                    try {
                        Thread.sleep(16);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }).start();
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {

    }

    private void draw() {
        Canvas canvas = mHolder.lockCanvas(); // 获取画布
        if (canvas == null) return;

        // 绘制缩放后的图像
        mMatrix.reset();
        mMatrix.setScale(mScaleFactor, mScaleFactor);
        canvas.drawBitmap(mBitmap, mMatrix, mPaint);

        mHolder.unlockCanvasAndPost(canvas); // 解锁画布，提交绘制内容
    }

    // 设置缩放比例
    public void setScale(float scale) {
        mScaleFactor = scale;
    }
}

2. 使用TextureView进行缩放

可以使用TextureView的缩放属性`setScaleX()`和`setScaleY()`来进行缩放操作，同时要开启硬件加速。

示例代码：

public class MyTextureView extends TextureView implements TextureView.SurfaceTextureListener {
    private SurfaceTexture mSurfaceTexture;
    private Paint mPaint;
    private Bitmap mBitmap;
    private float mScaleFactor = 1.0f;

    public MyTextureView(Context context) {
        super(context);
        init();
    }

    public MyTextureView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    private void init() {
        setSurfaceTextureListener(this);
        mPaint = new Paint();
    }

    @Override
    public void onSurfaceTextureAvailable(SurfaceTexture surface, int width, int height) {
        mSurfaceTexture = surface;
        mBitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
        draw();
    }

    @Override
    public void onSurfaceTextureSizeChanged(SurfaceTexture surface, int width, int height) {

    }

    @Override
    public boolean onSurfaceTextureDestroyed(SurfaceTexture surface) {
        return false;
    }

    @Override
    public void onSurfaceTextureUpdated(SurfaceTexture surface) {

    }

    private void draw() {
        Canvas canvas = lockCanvas(); // 获取画布
        if (canvas == null) return;

        // 绘制缩放后的图像
        canvas.save();
        canvas.scale(mScaleFactor, mScaleFactor);
        canvas.drawBitmap(mBitmap, 0, 0, mPaint);
        canvas.restore();

        unlockCanvasAndPost(canvas); // 解锁画布，提交绘制内容
    }

    // 设置缩放比例
    public void setScale(float scale) {
        mScaleFactor = scale;
        setScaleX(scale);
        setScaleY(scale);
    }
}