Android interface change shots, interception of the current screen picture

Some time ago the company has a need to do when we read the project need a magnifying glass, but how images are displayed at a finger in that circle, which we need to develop a position, or develop content control currently displays make a screenshot . We can get the shots we wanted View display corresponding to the following method

private Bitmap getScreenBm(View contentView) {
    Bitmap bm;
    contentView.destroyDrawingCache();
    contentView.setDrawingCacheEnabled(true);
    contentView.buildDrawingCache();
    bm = contentView.getDrawingCache();
    //指向的当前view的显示对象的缓存bm，如果view里控件增加等改变，bm相应改变
    return bm;
}

Here is what we want to return to the Bitmap to get the shots, we can make the appropriate Bitmap processing, in order to achieve the screenshot function.