/**
     * 生成视图的预览
     * @param activity   传context就好
     * @param v
     * @return  视图生成失败返回null
     *          视图生成成功返回视图的绝对路径
     */
    public static String saveImage(Activity activity, View v) {
        Bitmap bitmap;
        String path =  Environment.getExternalStorageDirectory().getAbsolutePath()  + "/preview.png";
        View view = activity.getWindow().getDecorView();
        view.setDrawingCacheEnabled(true);
        view.buildDrawingCache();
        bitmap = view.getDrawingCache();
        Rect frame = new Rect();
        activity.getWindow().getDecorView().getWindowVisibleDisplayFrame(frame);
        int[] location = new int[2];
        v.getLocationOnScreen(location);
        try {
//            bitmap = Bitmap.createBitmap(bitmap, location[0], location[1], v.getWidth(), v.getHeight());
            bitmap = Bitmap.createBitmap(bitmap, location[0]+18, location[1]+18, v.getWidth()-36, v.getHeight()-36);
            FileOutputStream fout = new FileOutputStream(path);
            bitmap.compress(Bitmap.CompressFormat.PNG, 50, fout);
            return path;
        } catch (FileNotFoundException e) {
            e.printStackTrace();
            Log.w("" ,"生成预览图片失败： "+e);
        } catch (IllegalArgumentException e) {
            Log.w("" ,"width is <= 0, or height is <= 0 "+e);
        } finally {
            // 清理缓存
            view.destroyDrawingCache();
            bitmap.recycle();
        }
        return null;

    }