Apps Canvas: why it's null and why it becomes z-higher of another views

[QuickNick]

I've created XML-layout and placed in it such views:
1)RelativeLayout with nested SurfaceView.
2)RelativeLayout with rotateable element.

This rotateable element should be over SurfaceView. But when I rotate element (only after that), it becomes hidden under SurfaceView. Also, I tried to fill canvas by transparent (alpha == 0) paint, but with no results.

Also, I tried to draw on the Canvas (I called getHolder() of SurfaceView and then lockCanvas(null) from SurfaceHolder) - but canvas is null.

 

[QuickNick]

Alternative question: I've tried to draw without SurfaceView, I've created the child of RelativeLayout.
In its constructor I called:

public CanvasHolder(Context context, AttributeSet attrs) {
        super(context, attrs);
        LayoutInflater layoutInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        layoutInflater.inflate(R.layout.canvas_holder, this);    
        this.draw(new Canvas());
    }

And then override method onDraw():

@Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        black.setARGB(255, 0, 0, 0);
        black.setAntiAlias(true);
        int halfWidth = this.getWidth() / 2;
        int height = this.getHeight();
        canvas.drawLine(0, 0, halfWidth, height, black);
    }

No line has been appeared on the view.