Bitmap bitmap=((BitmapDrawable)getResources().getDrawable(R.drawable.pull_down_color)).getBitmap();
Matrix matrix=new Matrix();
matrix.postRotate(180);
bitmap=Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), matrix, true);
iv_dow.setImageBitmap(bitmap);原文地址:http://blog.csdn.net/mingyue_1128/article/details/32116027