[Android存储]Shared Preferences

[引用 http://developer.android.com/guide/topics/data/data-storage.html#pref]
我们可以使用Shared Preferences来存储Key-Values对的私有数据，其中包括：booleans, floats, ints, longs, and strings.但是没有提供Object对象的存储。这些私有数据可以被持久的保存即使应用程序本身被关闭。

1）Shared Preferences提供了2个方法：
   a)getSharedPreferences(String name, int mode)
   当需要多个 preferences file时需要使用该方法通过名字来定义
   b)getPreferences(int mode)
   如果只需要使用一个preferences file无需使用名字
   c)mode的值：
   Activity.MODE_PRIVATE = 0x0000;
   where the created file can only be accessed by the calling application
   Activity.MODE_WORLD_READABLE = 0x0001;
   Allow all other applications to have read access
   Activity.MODE_WORLD_WRITEABLE = 0x0002;
   Allow all other applications to have write access
  
2)写入值到preferences file
   a)call edit() to get a SharedPreferences.Editor.
   b)Add values with methods such as putBoolean() and putString().
   c)Commit the new values with commit()

public class Calc extends Activity {
    public static final String PREFS_NAME = "MyPrefsFile";

    @Override
    protected void onCreate(Bundle state){
       super.onCreate(state);
       . . .

       // Restore preferences
       SharedPreferences settings = getSharedPreferences(PREFS_NAME, 0);
       // If only store one preferences file use below method
       // SharedPreferences settings = getSharedPreferences(0);
       boolean silent = settings.getBoolean("silentMode", false);
       setSilent(silent);
    }

    @Override
    protected void onStop(){
       super.onStop();

      // We need an Editor object to make preference changes.
      // All objects are from android.context.Context
      SharedPreferences settings = getSharedPreferences(PREFS_NAME, 0);
      // If only store one preferences file use below method
      SharedPreferences settings = getSharedPreferences([b][/b]0);
      SharedPreferences.Editor editor = settings.edit();
      editor.putBoolean("silentMode", mSilentMode);

      // Commit the edits!
      editor.commit();
    }
}