详解Android中的SharedPreferences

SharedPreferences sp = getSharedPreferences("sp_demo", Context.MODE_PRIVATE); 
sp.edit().putString("name", "小张").putInt("age", 11).commit(); 

SharedPreferences sp = getSharedPreferences("sp_demo", Context.MODE_PRIVATE); 
Editor editor = sp.edit(); 
editor.putString("name", "小张"); 
editor.putInt("age", 11); 
editor.commit(); 

SharedPreferences sp = getSharedPreferences("sp_demo", Context.MODE_PRIVATE); 
sp.edit().putString("name", "小张"); 
sp.edit().putInt("age", 11); 
sp.edit().commit(); 

SharedPreferences sp = getSharedPreferences("sp_demo", Context.MODE_PRIVATE); 
String name = sp.getString("name", null); 
int age = sp.getInt("age", 0); 
getSharedPreferences的具体实现是在frameworks/base/core/java/android/app/ContextImpl.java，代码如下：
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@Override 
public SharedPreferences getSharedPreferences(String name, int mode) { 
  SharedPreferencesImpl sp; 
  synchronized (ContextImpl.class) { 
    ...... 
    final String packageName = getPackageName(); 
    ArrayMap<String, SharedPreferencesImpl> packagePrefs = sSharedPrefs.get(packageName); 
    if (packagePrefs == null) { 
      packagePrefs = new ArrayMap<String, SharedPreferencesImpl>(); 
      sSharedPrefs.put(packageName, packagePrefs); 
    } 
    ...... 
    sp = packagePrefs.get(name); 
    if (sp == null) { 
      File prefsFile = getSharedPrefsFile(name); 
      sp = new SharedPreferencesImpl(prefsFile, mode); 
      packagePrefs.put(name, sp); 
      return sp; 
    } 
  } 
  ...... 
  return sp; 
}