SharedPreferences对数据的存储-CFANZ编程社区

SharedPreferences简介：

它的本质是基于XML文件存储key-value键值对数据，通常用来存储一些简单的配置信息，比如窗口状态，一些小型自定义数据等。其存储位置在/data/data/<包名>/shared_prefs目录下，可以通过DDMS--FileExplorer下查看（选中文件点击DDMS右上角的导出文件）。

数据的存储：

1.构造函数：

如示例，一般常用的构造函数为2个参数

第一个为sp的名称，第二个一般为权限比如Activity.MODE_PRIVATE, MODE_APPEND, MODE_WORLD_READABLE, MODE_WORLD_WRITEABLE

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);         


                   boolean silent = settings.getBoolean(         "silentMode"         ,          false         );         


                   setSilent(silent);         


                   }

2.数据的存储以及修改：

使用SharedPreferences.Editor类来构造一个编辑器进行存储数据

add.setOnClickListener(          new           OnClickListener(){          


                     @Override          


                     public           void           onClick(View v) {          


                     // TODO Auto-generated method stub          


                     String str_name = (String) name.getText();          


                     String str_path = (String) text.getText();          


                     SharedPreferences Addresses = getSharedPreferences(PREFS_NAME,Activity.M );          


                     SharedPreferences.Editor editor = Addresses.edit();          //通过SharedPreferences.edit()来对Editor进行初始化

editor.putString(str_name,str_path);          //添加数据 <br>                                                            editor.commit(); //数据添加后必须提交才会修改xml文件 <br>                               Toast.makeText(getApplicationContext(), "Successed", Toast.LENGTH_LONG).show(); <br>                         } <br>                        });

删除数据

public          boolean onItemLongClick(AdapterView<?> parent, View view,         


                   int          position,          long          id) {         


                   SharedPreferences Addresses = getSharedPreferences(PREFS_NAME,         


                   Activity.MODE_PRIVATE);         


                   SharedPreferences.Editor editor = Addresses.edit();             //通过SharedPreferences.edit()来对Editor进行初始化         


                   editor.         remove         ((String) listview.getSelectedItem());             //删除相应的数据         


                   editor.commit();            //同样需要提交         


                   }         


                  


                   });

3.一些常用的方法：

void apply() Commit your preferences changes back from this Editor to the `SharedPreferences` object it is editing.
Mark in the editor to remove all values from the preferences.
boolean commit() Commit your preferences changes back from this Editor to the `SharedPreferences` object it is editing.
Set a boolean value in the preferences editor, to be written back once `commit()` or `apply()` are called.
Set an int value in the preferences editor, to be written back once `commit()` or `apply()` are called.
Set a String value in the preferences editor, to be written back once `commit()` or `apply()` are called.
Set a set of String values in the preferences editor, to be written back once `commit()` is called.
Mark in the editor that a preference value should be removed, which will be done in the actual preferences once `commit()` is called.

数据的读取：

SharedPreferences.Editor edit() Create a new Editor for these preferences, through which you can make modifications to the data in the preferences and atomically commit those changes back to the SharedPreferences object.
Map<String, ?> getAll() Retrieve all values from the preferences.
boolean getBoolean(String key, boolean defValue) Retrieve a boolean value from the preferences.
Retrieve a String value from the preferences.
Retrieve a set of String values from the preferences.
void registerOnSharedPreferenceChangeListener(SharedPreferences.OnSharedPreferenceChangeListener listener) Registers a callback to be invoked when a change happens to a preference.
void unregisterOnSharedPreferenceChangeListener(SharedPreferences.OnSharedPreferenceChangeListener listener) Unregisters a previous callback.

使用getAll()读取所有数据存储在一个HashMap中：

listview = (ListView) findViewById(R.id.lv);          


          SharedPreferences Addresses = getSharedPreferences(PREFS_NAME, 0);         


          listItems = (HashMap<String, Object>) Addresses.getAll();

　　还是挺好用的哈～～