assets 读取文件
读取文字文件（txt，xml）

  InputStream is = getAssets().open("about.txt");                        int size = is.available();            byte[] buffer = new byte[size];            is.read(buffer);            is.close();            String text = new String(buffer);            TextView tv = (TextView)findViewById(R.id.text);            tv.setText(text);

 Bitmap bgImg = getImageFromAssetFile("background.png")