android 实现 surfaceview 缩放 平移

要实现SurfaceView的缩放和平移，可以通过以下步骤进行操作：

1. 创建一个SurfaceView并设置好SurfaceHolder.Callback回调函数。

2. 在SurfaceHolder.Callback的surfaceCreated()方法中，获取SurfaceView的宽度和高度，并创建一个Bitmap对象来存储SurfaceView的内容。

3. 在SurfaceHolder.Callback的surfaceChanged()方法中，根据SurfaceView的宽度和高度，将Bitmap对象的大小设置为SurfaceView的大小。

4. 在SurfaceHolder.Callback的surfaceDestroyed()方法中，释放Bitmap对象的内存空间。

5. 在SurfaceView的onTouchEvent()方法中，实现手势缩放和平移，并调用draw()方法重新绘制SurfaceView。

6. 在SurfaceView的draw()方法中，将Bitmap对象绘制在SurfaceView上。

下面是一个简单的示例代码：

public class MySurfaceView extends SurfaceView implements SurfaceHolder.Callback {

    private SurfaceHolder mHolder;
    private Bitmap mBitmap;
    private Canvas mCanvas;
    private float mScale = 1.0f;
    private float mTranslateX = 0.0f;
    private float mTranslateY = 0.0f;
    private float mLastX;
    private float mLastY;

    public MySurfaceView(Context context) {
        super(context);
        mHolder = getHolder();
        mHolder.addCallback(this);
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        mBitmap = Bitmap.createBitmap(getWidth(), getHeight(), Bitmap.Config.ARGB_8888);
        mCanvas = new Canvas(mBitmap);
    }

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

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        mBitmap.recycle();
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                mLastX = event.getX();
                mLastY = event.getY();
                break;
            case MotionEvent.ACTION_MOVE:
                float deltaX = event.getX() - mLastX;
                float deltaY = event.getY() - mLastY;
                mTranslateX += deltaX;
                mTranslateY += deltaY;
                mLastX = event.getX();
                mLastY = event.getY();
                break;
            case MotionEvent.ACTION_POINTER_DOWN:
                if (event.getPointerCount() == 2) {
                    float distance = distance(event);
                    mScale = distance / distance(event.getX(0), event.getY(0), event.getX(1), event.getY(1));
                }
                break;
            case MotionEvent.ACTION_POINTER_UP:
                if (event.getPointerCount() == 2) {
                    mScale = 1.0f;
                }
                break;
        }
        draw();
        return true;
    }

    private void draw() {
        Canvas canvas = mHolder.lockCanvas();
        if (canvas != null) {
            canvas.drawColor(Color.WHITE);
            canvas.drawBitmap(mBitmap, mTranslateX, mTranslateY, null);
            mHolder.unlockCanvasAndPost(canvas);
        }
    }

    private float distance(MotionEvent event) {
        return distance(event.getX(0), event.getY(0), event.getX(1), event.getY(1));
    }

    private float distance(float x1, float y1, float x2, float y2) {
        float deltaX = x2 - x1;
        float deltaY = y2 - y1;
        return (float) Math.sqrt(deltaX * deltaX + deltaY * deltaY);
    }
}

在上面的代码中，我们实现了手势缩放和平移功能，并在draw()方法中将Bitmap对象绘制在SurfaceView上。在onTouchEvent()方法中，我们检测到手势事件后，更新缩放和平移的参数，并调用draw()方法重新绘制SurfaceView。注意，我们使用lockCanvas()方法获取Canvas对象来绘制SurfaceView的内容，使用unlockCanvasAndPost()方法将Canvas对象提交到SurfaceView上显示。