Android 读取SD卡中的text文件内容

public class MainActivity extends ActionBarActivity {    private TextView mReadView;    private String SDPATH =  Environment.getExternalStorageDirectory().getPath() ;    private Handler mHandler = new Handler(){        @Override        public void handleMessage(Message msg) {            super.handleMessage(msg);            String text = msg.obj.toString();            mReadView.setText(text);        }    };    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        mReadView = (TextView)this.findViewById(R.id.read_text);        new Thread(new Runnable() {            @Override            public void run() {                String text =  readSDFile("test.txt");                Message message = new Message();                message.obj = text;                mHandler.sendMessage(message);            }        }).start();    }    public String readSDFile(String fileName) {        StringBuffer sb = new StringBuffer();        File file = new File(SDPATH + "//" + fileName);        try {            FileInputStream fis = new FileInputStream(file);            int c;            while ((c = fis.read()) != -1) {                if(Character.isWhitespace(c) ){//判断是否是空格                    continue;                }                sb.append((char) c);            }            fis.close();        } catch (FileNotFoundException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        }        Pattern p = Pattern.compile("\\s*|\t|\r|\n");        Matcher m = p.matcher(sb.toString());        return  m.replaceAll("");    }}