genBitmapFile for view offscreen

MainActivity.java

public static void genBitmapFile(Context context, View targetView, int num) {
        int sizePixels = 1080;

        Bitmap result = Bitmap.createBitmap(sizePixels, sizePixels, Bitmap.Config.ARGB_8888);
        Canvas c = new Canvas(result);

        // measure view first
        int sizeSpec = View.MeasureSpec.makeMeasureSpec(sizePixels, View.MeasureSpec.EXACTLY);
        targetView.measure(sizeSpec, sizeSpec);

        // then layout
        int width = targetView.getMeasuredWidth();
        int height = targetView.getMeasuredHeight();
        targetView.layout(0, 0, width, height);

        // now you can draw it
        targetView.draw(c);

        saveBitmapToFile(context, "testbm_" + num + ".png", result);
    }