/**   * 保存數據到手機rom的文件里面.   * @param context 應用程序的上下文 提供環境   * @param name 用戶名   * @param password 密碼   * @throws Exception   */public static void saveToRom(Context context, String name , String password) throws Exception{    //File file = new File("/data/data/com.itheima.login/files/info.txt");    File file = new File(context.getFilesDir(),"info.txt");//該文件在data下的files文件夾下getCacheDir()在cache文件夾下 文件大小不要超過1Mb    FileOutputStream fos = new FileOutputStream(file);    String txt = name+":"+password;    fos.write(txt.getBytes());    fos.flush();    fos.close();  }

/**   * 獲取保存的數據   * @param context   * @return   */public static Map<String,String> getUserInfo(Context context) {    File file = new File(context.getFilesDir(),"info.txt");    try {      FileInputStream fis = new FileInputStream(file);      //也可直接讀取文件String result = StreamTools.readFromStream(fis);      BufferedReader br = new BufferedReader(new InputStreamReader(fis));      String str = br.readLine();      String[] infos = str.split(":");      Map<String,String> map = new HashMap<String, String>();      map.put("username", infos[0]);      map.put("password", infos[1]);      return map;    } catch(Exception e) {      e.printStackTrace();      return null;    }  }//最后可以直接調用上面的方法讀取信息Map<String, String> map = getUserInfo(this);If(map!=null){Textview.setText(map.get(“username”));}

File path = Environment.getExternalStorageDirectory();    StatFs stat = new StatFs(path.getPath());    long blockSize = stat.getBlockSize();    long totalBlocks = stat.getBlockCount();    long availableBlocks = stat.getAvailableBlocks();    long totalSize = blockSize*totalBlocks;    long availSize = blockSize * availableBlocks;    String totalStr = Formatter.formatFileSize(this,totalSize);    String availStr = Formatter.formatFileSize(this, availSize);    tv.setText("總空間"+totalStr+"/n"+"可用空間"+availStr);

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>public static void save(String name ,String password) throws Exception{if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){File file = new File(Environment.getExternalStorageDirectory(),"info.txt");//也可直接寫/sdcard/info.txt 先判斷sd卡是否存在    FileOutputStream fos = new FileOutputStream(file);    String txt = name+":"+password;    fos.write(txt.getBytes());    fos.flush();    fos.close();// 使用RandomAccessFile像文件追加內容FileOutputStream會把原有的文件內容清空//RandomAccessFile raf = new RandomAccessFile(file,"rw");//raf.seek(file.length()); 將文件指針移動到最后//raf.write(name.getBytes()+password.getBytes());//raf.close();  }}

//讀取文件 加入讀取權限public static String read(){      try {        if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){          File sdcardDir = Environment.getExternalStorageDirectory();          FileInputStream fis = new FileInputStream(sdcardDir.getCanonicalPath() + "info.txt");          BufferedReader br = new BufferedReader(new InputStreamReader(fis));          StringBuilder sb = new StringBuilder("");          String line = null;          while ((line = br.readLine())!= null){            sb.append(line);          }          return sb.toString();        }      } catch (Exception e) {        e.printStackTrace();      }      return null;    }

public class MySharedPreference {  private Context context;  private SharedPreferences sp ;  private Editor edit;  public MySharedPreference(Context context){    this.context = context;  }  public boolean saveMessage(String name,String pwd){    boolean flag = false;     sp = context.getSharedPreferences("userInfo",Context.MODE_PRIVATE);     //MODE定義了訪問的權限現在是本應用可以訪問    edit = sp.edit();    edit.putString("name", name);    edit.putString("pwd", pwd);    flag = edit.commit();//提交事務將數據持久化到存儲器中    return flag;  }  public Map<String,Object> getMessage(){    Map<String,Object> map = new HashMap<String, Object>();    sp = context.getSharedPreferences("userInfo", Context.MODE_PRIVATE);    String name = sp.getString("name", "");    String pwd = sp.getString("pwd", "");    map.put("name", name);    map.put("pwd",pwd);    return map;  }}