Android 提供了2种可选的数据存储方式，分别是：内部存储(Shared Preferences,File,Database)，外部存储(SDCard，网络存储)。 至于选用里面的哪种主要取决于下面2个原因：

1.数据是否公开给其他APP使用？

2.需要多大的存储空间？

Android利用Content Provider 可以把当前APP的私有数据暴露给其他APP。其他APP可以读写操作你的APP数据。

一、Shared Preferences

生命周期：存储在shared preferences的数据，可以被你整个APP程序使用，即时你的APP被KILL掉了，数据还是会保存在那里，实际上就是以XML的形式保存在data/data/你的包名/shared_prefs/目录下面， 文件名：你的perferences名称.xml

适用场景：数据量比较少； 是key-value的基本数据类型，例如：boolean, float,int,long,和string。

测试例子：

写入数据：

//get the preferences, then editor, set a data item
SharedPreferences appPrefs = getSharedPreferences("config", 0);
SharedPreferences.Editor prefsEd = appPrefs.edit();
prefsEd.putString("site", "www.ahuoo.com");
prefsEd.commit();

你可以在其他activity读取site的值：

//get the preferences then retrieve saved data, specifying a default value
SharedPreferences appPrefs = getSharedPreferences("config", 0);
String savedData = appPrefs.getString("site", "www.ahuoo.com");

通过eclipse的 File Explorer窗口，可以查看shared preferences在模拟器里面的存储情况, 打开对应的preferences文件config.xml文件，内容如下:

<?xml version='1.0' encoding='utf-8' standalone='yes' ?>
<map>
<string name="site">www.ahuoo.com</string>
</map>

更多内容参看PPT>>>>>>>>>>>>>>>>>>>>>>>下载 Android存储.pptx

Activity A 中的write data测试代码：

     //sharedPreferences storage
	   SharedPreferences sp = getSharedPreferences("config",Context.MODE_PRIVATE);
	   String state = sp.getString("state", "");
	   ToastUtil.shortTips(mContext, state);
	   if(state.equals("")){
	       SharedPreferences.Editor edit = sp.edit();
	       edit.putString("state", "category list activity");
	       edit.putBoolean("bKey", true);
	       edit.putFloat("fKey", 0.57f);
	       edit.putLong("lKey", 23423L);
	       edit.putInt("iKey", 33);

	       edit.commit();
	       ToastUtil.shortTips(mContext, sp.getString("state", "null-2"));
	   }

	   //file storage
	   try {
            FileOutputStream fos = this.openFileOutput("test.txt",Context.MODE_PRIVATE);
            fos.write("file storage: hello.".getBytes());
            fos.close();
       } catch (Exception e) {
            e.printStackTrace();
       }

	   //sd card
	   if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
	       File sdDir = Environment.getExternalStorageDirectory();
	       Log.v(TAG,"sdDir=" + sdDir);
	       File file = new File(sdDir,"sd.txt");
	       try {
	            FileOutputStream fos = new FileOutputStream(file);
	            fos.write("sd storage: world.".getBytes());
	            fos.close();
           } catch (Exception e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
           }
	   }

	   //database
	   SQLiteDatabase db = this.openOrCreateDatabase("test2.db", Context.MODE_PRIVATE, null);
	   String sql = "create table if not exists tb_test(id integer default '1' not null primary key autoincrement," +
        	   		"name text not null," +
        	   		"content text not null)";
	   db.execSQL(sql);
	   for(int i=0; i<5; i++){
	       String sqlInsert = "insert into tb_test(name,content) values('ahu"+i+"','我是阿虎，批量插入')";
	       db.execSQL(sqlInsert);
	   }
	   ContentValues cv = new ContentValues();
	   cv.put("name", "caih");
	   cv.put("content", "我是阿虎，ContentValues插入的");
	   db.insert("tb_test",null,cv);
	   db.close();

在另外一个activity B里面使用这些存储方式的测试代码：

     //sharedPreferences
       SharedPreferences sp = getSharedPreferences("config",0);
       String state = sp.getString("state", "null-3");
       ToastUtil.shortTips(mContext, state);
       SharedPreferences.Editor edit = sp.edit();
       edit.putString("state", "goods list activity");
       edit.commit();
       ToastUtil.shortTips(mContext, sp.getString("state", "null-4"));

       //file storage
       try {
           FileInputStream fis = this.openFileInput("test.txt");
           ByteArrayOutputStream bos = new ByteArrayOutputStream();
           byte[] buffer = new byte[1024];
           int len = -1;
           while((len=fis.read(buffer)) != -1){
               bos.write(buffer, 0, len);
           }
           ToastUtil.shortTips(mContext, bos.toString());
           bos.close();
           fis.close();
       } catch (Exception e) {
            e.printStackTrace();
       }

       //sd card storage
       if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
           try {
               FileInputStream fis = new FileInputStream(new File(Environment.getExternalStorageDirectory(),"sd.txt"));
               byte[] buffer = new byte[1024];
               StringBuffer sb = new StringBuffer();
               while(fis.read(buffer)!=-1){
                   sb.append(new String(buffer));
               }
               ToastUtil.shortTips(mContext, sb.toString());
            } catch (Exception e) {
                e.printStackTrace();
            }
       }

       //raw folder
       try {
           Resources res = this.getResources();
           InputStream is = res.openRawResource(R.raw.appconfig);
           byte[] buffer = new byte[1024];
           StringBuffer sb = new StringBuffer();
           while(is.read(buffer) != -1){
               ToastUtil.shortTips(mContext, "raw file content: " + new String(buffer));
           }
       } catch (Exception e) {
           e.printStackTrace();
       }

       //database
       SQLiteDatabase db = this.openOrCreateDatabase("test2.db", Context.MODE_PRIVATE, null);
       Cursor cur = db.rawQuery("select * from tb_test order by id desc limit 5 ", null);

       while(cur.moveToNext()){
           int id = cur.getInt(cur.getColumnIndex("id"));
           String name = cur.getString(cur.getColumnIndex("name"));
           String content = cur.getString(2);
           Log.i(TAG, id + "," + name + "," + content);
       }
       cur.close();
       db.close();