Android SharedPreferences存储的正确写法
SharedPreferences特点
即便是Android小白都知道的SharedPreferences的用法，这是保存数据最简便的方法，但是不处理好的话后期维护将是一个巨大的坑。那么该如何处理好SharedPreferences才方便维护呢。先从它的特点开始入手吧。
- 通过Context.getSharedPreferences()获取的SharedPreferences是一个单例
- SharedPreferences.edit()每次都会创建一个新的编辑对象，commit()之前一切改动都无效
SharedPreferences的具体实现并不在公开API内，创建方法只有通过Context获取。具体实现我们不去研究，通过Log打印每次获取的对象都是同一个，同样的方法可知道每次edit()都会得到不同的对象。
难以维护的SharedPreferences
SharedPreferenceuserPreferences=context.getSharedPreferences("UserInfo",Context.MODE_PRIVATE);
userPreferences.edit()
.putString("id","myId")
.putString("name","myName")
.putString("head","myHead")
.commit();
Log.e("id",userPreferences.getString("id",""));
Log.e("name",userPreferences.getString("name",""));
Log.e("head",userPreferences.getString("head",""));
如上一段SharedPreferences保存和读取的方法非常简便，正因此才不易维护，可能因为写错Key而找不出问题所在，当然一般我们都会把Key写成静态常量。但随着项目增大，可能需要多处修改用户信息，每次都要一个个put(),除了写着厌烦看着难受，当遇到需要增加或减少字段时也非常不便。
SharedPreferences该这么写
如果能保留原有写法，又能规范方法那是最好不过了，看下SharedPreferences的接口方法并不多，很容易就写个包装类封装下。
importandroid.content.SharedPreferences;
importandroid.support.annotation.Nullable;
importjava.util.Map;
importjava.util.Set;
/**
*SharedPreferences包装类
*Createdbywittytutuon17-3-29.
*/
publicclassPreferencesWrapperimplementsSharedPreferences{
protectedSharedPreferencesmPreferences;
publicPreferencesWrapper(SharedPreferencespreferences){
mPreferences=preferences;
}
@Override
publicMapgetAll(){
returnmPreferences.getAll();
}
@Nullable
@Override
publicStringgetString(Stringkey,@NullableStringdefValue){
returnmPreferences.getString(key,defValue);
}
@Nullable
@Override
publicSetgetStringSet(Stringkey,@NullableSetdefValues){
returnmPreferences.getStringSet(key,defValues);
}
@Override
publicintgetInt(Stringkey,intdefValue){
returnmPreferences.getInt(key,defValue);
}
@Override
publiclonggetLong(Stringkey,longdefValue){
returnmPreferences.getLong(key,defValue);
}
@Override
publicfloatgetFloat(Stringkey,floatdefValue){
returnmPreferences.getFloat(key,defValue);
}
@Override
publicbooleangetBoolean(Stringkey,booleandefValue){
returnmPreferences.getBoolean(key,defValue);
}
@Override
publicbooleancontains(Stringkey){
returnmPreferences.contains(key);
}
@Override
publicEditorWrapperedit(){
returnnewEditorWrapper(mPreferences.edit());
}
@Override
publicvoidregisterOnSharedPreferenceChangeListener(OnSharedPreferenceChangeListenerlistener){
mPreferences.registerOnSharedPreferenceChangeListener(listener);
}
@Override
publicvoidunregisterOnSharedPreferenceChangeListener(OnSharedPreferenceChangeListenerlistener){
mPreferences.unregisterOnSharedPreferenceChangeListener(listener);
}
publicstaticclassEditorWrapperimplementsEditor{
protectedEditormEditor;
publicEditorWrapper(Editoreditor){
mEditor=editor;
}
@Override
publicEditorWrapperputString(Stringkey,@NullableStringvalue){
mEditor.putString(key,value);
returnthis;
}
@Override
publicEditorWrapperputStringSet(Stringkey,@NullableSetvalues){
mEditor.putStringSet(key,values);
returnthis;
}
@Override
publicEditorWrapperputInt(Stringkey,intvalue){
mEditor.putInt(key,value);
returnthis;
}
@Override
publicEditorWrapperputLong(Stringkey,longvalue){
mEditor.putLong(key,value);
returnthis;
}
@Override
publicEditorWrapperputFloat(Stringkey,floatvalue){
mEditor.putFloat(key,value);
returnthis;
}
@Override
publicEditorWrapperputBoolean(Stringkey,booleanvalue){
mEditor.putBoolean(key,value);
returnthis;
}
@Override
publicEditorWrapperremove(Stringkey){
mEditor.remove(key);
returnthis;
}
@Override
publicEditorWrapperclear(){
mEditor.clear();
returnthis;
}
@Override
publicbooleancommit(){
returnmEditor.commit();
}
@Override
publicvoidapply(){
mEditor.apply();
}
}
}
接下来的使用就简单了
publicclassUserInfoPreferencesextendsPreferencesWrapper{
privatestaticfinalStringNAME="UserInfo";
publicstaticfinalKEY_ID="id"
publicstaticfinalKEY_NAME="name";
publicstaticfinalKEY_HEAD="head";
publicstaticfinalKEY_SEX="sex";
privatestaticvolatileUserInfoPreferencesmPreferences;
publicstaticUserInfoPreferencesgetInstance(Contextcontext){
if(mPreferences==null){
synchronized(UserInfoPreferences.class){
if(mPreferences==null){
SharedPreferencespreferences=context.getApplicationCtontext().getShaedPreferences(NAME,Context.MODE_PRIVATE);
mPreferences=newUserInfoPreferences(preferences);
}
}
}
returnmPreferences;
}
publicUserInfoPreferences(SharedPreferencespreferences){
super(preferences);
}
//获取用户信息
publicUserInfogetUserInfo(){
Stringid=mPreferences.getString(KEY_ID,"");
Stringname=mPreferences.getString(KEY_NAME,"");
Stringhead=mPreferences.getString(KEY_HEAD,"");
returnnewUserInfo(id,name,head);
}
@Override
publicEditoredit(){
returnnewEditor(mPreferences.edit());
}
publicstaticclassEditorextendsEditorWrapper{
publicEditor(SharedPreferences.Editoreditor){
super(editor);
}
//保存用户信息
publicEditorputUserInfo(Stringid,Stringname,Stringhead){
mEditor.putString(KEY_ID,id)
.putString(KEY_AME,name)
.putString(KEY_HEAD,head);
returnthis;
}
//清空用户信息
publicEditorclearUserInfo(){
mEditor.remove(KEY_ID)
.remove(KEY_NAME)
.remove(KEY_HEAD);
returnthis;
}
}
}
调用即方便扩展，也保留了原有方法。
UserInfoPreferencespreferences=UserInfoPreferences.getInstance(context);
preferences.edit()
.clearUserInfo()
.putUserInfo("myId","myName","myHead")
.putInt(KEY_SEX,0)
.commit();
UserInfouserInfo=preferences.getUserInfo();
intsex=preferences.getInt(KEY_SEX,0);
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