问题描述

不同 activity 中的 SharedPreferences

我用下面的代码从 activity A 中加载 SharedPreferences：

private void SavePreferences(String key String value){    SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);    SharedPreferences.Editor editor = sharedPreferences.edit();    editor.putString(key value);    editor.commit();   }

在 activity B 中我想加载 SharedPreferences。下面是一个异常 NullPointerException:

private void LoadPreferences(){          SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);       data = sharedPreferences.getString(""name""08:00"") ;   }

我用下面的代码，得到这个编译错误：""No enclosing instance of the type A is accessible in scope""

 private void LoadPreferences(){          SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(A.this);       data = sharedPreferences.getString(""name""08:00"") ;   }

如何访问数据？谢谢！

解决方案

在两个 Activities 中把 this 替换为 getApplicationContext()
在Activity A 的 SharedPreferences 是下面的方式：

private void SavePreferences(String key String value){        SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(getApplicationContext());        SharedPreferences.Editor editor = sharedPreferences.edit();        editor.putString(key value);        editor.commit();        Intent sd=new Intent(thisSecongtess.class);        startActivity(sd);       }

Activity B 中按下面的方式获取值：

 private void LoadPreferences(){          SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(getApplicationContext());     String  data = sharedPreferences.getString(""name""08:00"") ;     Toast.makeText(thisdata Toast.LENGTH_LONG).show();   }

解决方案二：
在 shared preferences 中存储值

SharedPreferences preferences==PreferenceManager.getDefaultSharedPreferences(this);  SharedPreferences.Editor editor=preferences.edit();  editor.putString(""Name""Harneet"");  editor.commit();

从 shared preferences 中检索值:

SharedPreferences preferences==PreferenceManager.getDefaultSharedPreferences(this);  String name=preferences.getString(""Name""");  if(!name.equalsIgnoreCase(""""))  {    name=name+""  Sethi"";  /* 编辑值 */  }

从 sharedpreference 中编辑数据

SharedPreferences.Editor editor = getPreferences(MODE_PRIVATE).edit(); editor.putString(""text"" mSaved.getText().toString()); editor.putInt(""selection-start"" mSaved.getSelectionStart()); editor.putInt(""selection-end"" mSaved.getSelectionEnd()); editor.commit();

从 shared preference 中检索数据

SharedPreferences prefs = getPreferences(MODE_PRIVATE); String restoredText = prefs.getString(""text"" null);if (restoredText != null) {  //mSaved.setText(restoredText TextView.BufferType.EDITABLE);  int selectionStart = prefs.getInt(""selection-start"" -1);  int selectionEnd = prefs.getInt(""selection-end"" -1);  /*if (selectionStart != -1 && selectionEnd != -1)  {     mSaved.setSelection(selectionStart selectionEnd);  }*/}