Using Shared Preferences

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本文详细介绍了SharedPreferences在Android应用中如何存储和读取基本类型的键值对数据，包括布尔值、浮点数、整数、长整数及字符串等。通过示例展示了如何在计算器应用中保存静音按键模式的偏好设置。

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SharedPreferences 类类似windows下的ini文件，用于存储一些配置信息。

The SharedPreferences class provides a general framework that allows you to save and retrieve persistent key-value pairs of primitive data types. You can use SharedPreferences to save any primitive data: booleans, floats, ints, longs, and strings. This data will persist across user sessions (even if your application is killed).

User Preferences

Shared preferences are not strictly for saving "user preferences," such as what ringtone a user has chosen. If you're interested in creating user preferences for your application, see PreferenceActivity , which provides an Activity framework for you to create user preferences, which will be automatically persisted (using shared preferences).

To get a SharedPreferences object for your application, use one of two methods:

getSharedPreferences() - Use this if you need multiple preferences files identified by name, which you specify with the first parameter.
getPreferences() - Use this if you need only one preferences file for your Activity. Because this will be the only preferences file for your Activity, you don't supply a name.

To write values:

Call edit() to get a SharedPreferences.Editor .
Add values with methods such as putBoolean() and putString() .
Commit the new values with commit()

To read values, use SharedPreferences methods such as getBoolean() and getString() .

Here is an example that saves a preference for silent keypress mode in a calculator:

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,

MODE_PRIVATE

);//提供文件名，可设置读写权限
       // getPreferences(MODE_PRIVATE);   //不提供文件参数，默认为工程名。在工程的私有文件夹的share_prefs可找到相应的文件
       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,

MODE_PRIVATE

);
      SharedPreferences.Editor editor = settings.edit();
      editor.putBoolean("silentMode", mSilentMode);
      // Commit the edits!
      editor.commit();
    }



}