Android通过反射打造可以存储任何对象的万能SharedPreferences_android obj.getclass().getfield("type"); 存储类型-优快云博客

我们通常使用SharedPreferences存储一些需要保存在本地，但又不至于存储在数据库里的一些数据，一般我们用它来存储一些用户名，密码等数据是非常方便的，那么如果我们想要存储的信息有10几条，我们就得写10几行重复的代码把他们存进去，取出来的时候还得写10几行代码将他们一条一条取出来，那么有没有什么办法可以只需要一行代码就可以将他们存进去，一行代码就将他们取出来？答案是有的，这篇文章我们就介绍如何通过反射来实现。

1.将我们想要保存的数据封装成一个实体类 Person.java 其中属性我们都用Public来修饰

 
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            public 
            
            class 
            
            Person 
            
            {
           
            //String类型属性 姓名
           
            public 
            
            String 
            
            name
            
            ;
           
            //int类型属性 年龄
           
            public 
            
            int 
            
            age
            
            ;
           
            //float类型属性 身高
           
            public 
            
            float 
            
            height
            
            ;
           
            //boolean类型属性 是否已婚
           
            public 
            
            boolean 
            
            isMarried
            
            ;
           
            //String类型属性 证件号
           
            public 
            
            String 
            
            id
            
            ;
           
            }

来自CODE的代码片
Person.java

2.通过反射，将Person类中的属性取出来

 
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             public 
             
             class 
             
             SharedPreferencesUtils 
             
             {
            
             /**
            
             	 * 根据传入的对象，取出其中用public修饰符修饰的属性
            
             	 * @param clazz 想要拿到属性的类的字节码文件
            
             	 * @return 所有用pulic修饰的属性的一个list表
            
             	 */
            
             public 
             
             static 
             
             <
             
             T
             
             > 
             
             List
             
             <
             
             Field
             
             > 
             
             getPublicFields
             
             (
             
             Class
             
             <?> 
             
             clazz
             
             ){
            
             if 
             
             (
             
             clazz
             
             .
             
             equals
             
             (
             
             Object
             
             .
             
             class
             
             )) 
             
             {
            
             return 
             
             null
             
             ;
            
             }
            
             //用来存储clazz中用public修饰的属性的list
            
             List
             
             <
             
             Field
             
             > 
             
             list 
             
             = 
             
             new 
             
             ArrayList
             
             <
             
             Field
             
             >();
            
             //获得clazz中所有用public修饰的属性
            
             Field
             
             [] 
             
             fields 
             
             = 
             
             clazz
             
             .
             
             getFields
             
             ();
            
             //将fields加入到list中
            
             for
             
             (
             
             int 
             
             i
             
             =
             
             0 
             
             ; 
             
             i
             
             <
             
             fields
             
             .
             
             length 
             
             ; 
             
             i
             
             ++){
            
             list
             
             .
             
             add
             
             (
             
             fields
             
             [
             
             i
             
             ]);
            
             }
            
             return 
             
             list
             
             ;
            
             }

来自CODE的代码片
SharedPreferencesUtils.java

我们先来测试一下属性有没有被取出来，我们在MainActivity.java中添加如下代码进行测试

 
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              public 
              
              class 
              
              MainActivity 
              
              extends 
              
              Activity 
              
              {
             
              @Override
             
              protected 
              
              void 
              
              onCreate
              
              (
              
              Bundle 
              
              savedInstanceState
              
              ) 
              
              {
             
              super
              
              .
              
              onCreate
              
              (
              
              savedInstanceState
              
              );
             
              setContentView
              
              (
              
              R
              
              .
              
              layout
              
              .
              
              activity_main
              
              );
             
              //调用我们刚刚写好的方法来获取Person类中的属性
             
              List
              
              <
              
              Field
              
              > 
              
              publicFields 
              
              = 
              
              SharedPreferencesUtils
              
              .
              
              getPublicFields
              
              (
              
              Person
              
              .
              
              class
              
              );
             
              for
              
              (
              
              Field 
              
              f 
              
              : 
              
              publicFields
              
              ){
             
              String 
              
              name 
              
              = 
              
              f
              
              .
              
              getName
              
              ();
             
              Log
              
              .
              
              i
              
              (
              
              "TAG"
              
              , 
              
              name
              
              +
              
              "\n"
              
              );
             
              }
             
              }
             
              }

来自CODE的代码片
MainActivity.java

我们来看一下Log打印的信息

我们可以看到，Person中的属性我们都已经拿到了

3.将对象存储到SharedPreferences中

 
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               public 
               
               static 
               
               void 
               
               putObjectToShare
               
               (
               
               String 
               
               shareName 
               
               , 
               
               Object 
               
               obj
               
               ){
              
               //获得SharedPreferences实例
              
               SharedPreferences 
               
               sharedPreferences 
               
               = 
               
               mContext
               
               .
               
               getSharedPreferences
               
               (
               
               shareName
               
               ,
               
               Activity
               
               .
               
               MODE_PRIVATE
               
               );
              
               //获得Editor
              
               Editor 
               
               edit 
               
               = 
               
               sharedPreferences
               
               .
               
               edit
               
               ();
              
               //存储数据之前先将之前的旧数据清掉
              
               edit
               
               .
               
               clear
               
               ();
              
               //调用commit提交数据(这里为了清掉数据)
              
               edit
               
               .
               
               commit
               
               ();
              
               List
               
               <
               
               Field
               
               > 
               
               publicFields 
               
               = 
               
               getPublicFields
               
               (
               
               obj
               
               .
               
               getClass
               
               ());
              
               for
               
               (
               
               Field 
               
               f 
               
               : 
               
               publicFields
               
               ){
              
               String 
               
               name 
               
               = 
               
               f
               
               .
               
               getName
               
               ();
              
               try 
               
               {
              
               //获得当前属性的类型和值
              
               //类型的话如果是基本类型，会自动装箱
              
               Object 
               
               type 
               
               = 
               
               f
               
               .
               
               get
               
               (
               
               obj
               
               );
              
               //判断各种类型，调用各种类型的put方法将数据存储进去
              
               if 
               
               (
               
               type 
               
               instanceof 
               
               String
               
               ) 
               
               {
              
               edit
               
               .
               
               putString
               
               (
               
               name
               
               , 
               
               (
               
               String
               
               ) 
               
               type
               
               );
              
               }
               
               else 
               
               if 
               
               (
               
               type 
               
               instanceof 
               
               Integer
               
               ) 
               
               {
              
               edit
               
               .
               
               putInt
               
               (
               
               name
               
               , 
               
               (
               
               Integer
               
               ) 
               
               type
               
               );
              
               }
               
               else 
               
               if 
               
               (
               
               type 
               
               instanceof 
               
               Float
               
               ) 
               
               {
              
               edit
               
               .
               
               putFloat
               
               (
               
               name
               
               , 
               
               (
               
               Float
               
               ) 
               
               type
               
               );
              
               }
               
               else 
               
               if 
               
               (
               
               type 
               
               instanceof 
               
               Long
               
               ) 
               
               {
              
               edit
               
               .
               
               putLong
               
               (
               
               name
               
               , 
               
               (
               
               Long
               
               ) 
               
               type
               
               );
              
               }
               
               else 
               
               if 
               
               (
               
               type 
               
               instanceof 
               
               Boolean
               
               ) 
               
               {
              
               edit
               
               .
               
               putBoolean
               
               (
               
               name
               
               , 
               
               (
               
               Boolean
               
               ) 
               
               type
               
               );
              
               }
              
               } 
               
               catch 
               
               (
               
               Exception 
               
               e
               
               ) 
               
               {
              
               e
               
               .
               
               printStackTrace
               
               ();
              
               }
              
               //调用commit，提交数据
              
               edit
               
               .
               
               commit
               
               ();
              
               }
              
               }

来自CODE的代码片
SharedPreferencesUtils.java

4.将对象从SharedPreferences中取出来

 
          <a target=_blank id="L1" href="http://blog.youkuaiyun.com/nugongahou110/article/details/46913461#L1" rel="#L1" style="color: rgb(102, 102, 102); text-decoration: none;">  1</a>
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<a target=_blank id="L3" href="http://blog.youkuaiyun.com/nugongahou110/article/details/46913461#L3" rel="#L3" style="color: rgb(102, 102, 102); text-decoration: none;">  3</a>
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<a target=_blank id="L20" href="http://blog.youkuaiyun.com/nugongahou110/article/details/46913461#L20" rel="#L20" style="color: rgb(102, 102, 102); text-decoration: none;"> 20</a>
<a target=_blank id="L21" href="http://blog.youkuaiyun.com/nugongahou110/article/details/46913461#L21" rel="#L21" style="color: rgb(102, 102, 102); text-decoration: none;"> 21</a>
<a target=_blank id="L22" href="http://blog.youkuaiyun.com/nugongahou110/article/details/46913461#L22" rel="#L22" style="color: rgb(102, 102, 102); text-decoration: none;"> 22</a>
<a target=_blank id="L23" href="http://blog.youkuaiyun.com/nugongahou110/article/details/46913461#L23" rel="#L23" style="color: rgb(102, 102, 102); text-decoration: none;"> 23</a>
<a target=_blank id="L24" href="http://blog.youkuaiyun.com/nugongahou110/article/details/46913461#L24" rel="#L24" style="color: rgb(102, 102, 102); text-decoration: none;"> 24</a>
<a target=_blank id="L25" href="http://blog.youkuaiyun.com/nugongahou110/article/details/46913461#L25" rel="#L25" style="color: rgb(102, 102, 102); text-decoration: none;"> 25</a>
<a target=_blank id="L26" href="http://blog.youkuaiyun.com/nugongahou110/article/details/46913461#L26" rel="#L26" style="color: rgb(102, 102, 102); text-decoration: none;"> 26</a>
<a target=_blank id="L27" href="http://blog.youkuaiyun.com/nugongahou110/article/details/46913461#L27" rel="#L27" style="color: rgb(102, 102, 102); text-decoration: none;"> 27</a>
<a target=_blank id="L28" href="http://blog.youkuaiyun.com/nugongahou110/article/details/46913461#L28" rel="#L28" style="color: rgb(102, 102, 102); text-decoration: none;"> 28</a>
<a target=_blank id="L29" href="http://blog.youkuaiyun.com/nugongahou110/article/details/46913461#L29" rel="#L29" style="color: rgb(102, 102, 102); text-decoration: none;"> 29</a>
<a target=_blank id="L30" href="http://blog.youkuaiyun.com/nugongahou110/article/details/46913461#L30" rel="#L30" style="color: rgb(102, 102, 102); text-decoration: none;"> 30</a>
<a target=_blank id="L31" href="http://blog.youkuaiyun.com/nugongahou110/article/details/46913461#L31" rel="#L31" style="color: rgb(102, 102, 102); text-decoration: none;"> 31</a>
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<a target=_blank id="L35" href="http://blog.youkuaiyun.com/nugongahou110/article/details/46913461#L35" rel="#L35" style="color: rgb(102, 102, 102); text-decoration: none;"> 35</a>
<a target=_blank id="L36" href="http://blog.youkuaiyun.com/nugongahou110/article/details/46913461#L36" rel="#L36" style="color: rgb(102, 102, 102); text-decoration: none;"> 36</a>
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<a target=_blank id="L38" href="http://blog.youkuaiyun.com/nugongahou110/article/details/46913461#L38" rel="#L38" style="color: rgb(102, 102, 102); text-decoration: none;"> 38</a>
<a target=_blank id="L39" href="http://blog.youkuaiyun.com/nugongahou110/article/details/46913461#L39" rel="#L39" style="color: rgb(102, 102, 102); text-decoration: none;"> 39</a> 
              
                public 
                
                static 
                
                <
                
                T
                
                > 
                
                T 
                
                getObjectFromShare
                
                (
                
                String 
                
                shareName 
                
                , 
                
                Class
                
                <
                
                T
                
                > 
                
                clazz
                
                ){
               
                //获得SharedPreferences实例
               
                SharedPreferences 
                
                sharedPreferences 
                
                = 
                
                mContext
                
                .
                
                getSharedPreferences
                
                (
                
                shareName
                
                , 
                
                Activity
                
                .
                
                MODE_PRIVATE
                
                );
               
                //T是一个泛型，根据clazz不同而不同
               
                T 
                
                t 
                
                = 
                
                null
                
                ;
               
                try 
                
                {
               
                //获得sharedPreferences中所有的数据，数据为键值对保存在map中
               
                Map
                
                <
                
                String
                
                ,?> 
                
                map 
                
                = 
                
                sharedPreferences
                
                .
                
                getAll
                
                ();
               
                //调用getPublicFields方法得到clazz中所有的公有属性
               
                List
                
                <
                
                Field
                
                > 
                
                publicFields 
                
                = 
                
                getPublicFields
                
                (
                
                clazz
                
                );
               
                //如果两者都不为空的话
               
                if 
                
                (
                
                map
                
                .
                
                size
                
                ()>
                
                0 
                
                && 
                
                publicFields
                
                .
                
                size
                
                ()>
                
                0
                
                ) 
                
                {
               
                //将T实例化出来
               
                t 
                
                = 
                
                clazz
                
                .
                
                newInstance
                
                ();
               
                //遍历map中所有的键值对
               
                for
                
                (
                
                Map
                
                .
                
                Entry
                
                <
                
                String
                
                ,?> 
                
                entry 
                
                : 
                
                map
                
                .
                
                entrySet
                
                ()){
               
                //map中的键
               
                String 
                
                key 
                
                = 
                
                entry
                
                .
                
                getKey
                
                ();
               
                //map中的值
               
                Object 
                
                value 
                
                = 
                
                entry
                
                .
                
                getValue
                
                ();
               
                //遍历clazz中的所有公有属性
               
                for
                
                (
                
                Field 
                
                field 
                
                : 
                
                publicFields
                
                ){
               
                //获得属性名
               
                String 
                
                name 
                
                = 
                
                field
                
                .
                
                getName
                
                ();
               
                //如果属性名与键相同
               
                if 
                
                (
                
                name
                
                .
                
                equalsIgnoreCase
                
                (
                
                key
                
                )) 
                
                {
               
                //相当于给对象T中的属性field赋值，值为value
               
                field
                
                .
                
                set
                
                (
                
                t
                
                , 
                
                value
                
                );
               
                break
                
                ;
               
                }
               
                }
               
                }
               
                }
               
                } 
                
                catch 
                
                (
                
                Exception 
                
                e
                
                ) 
                
                {
               
                e
                
                .
                
                printStackTrace
                
                ();
               
                }
               
                //整个遍历结束后，我们的对象中的属性也都有值了
               
                return 
                
                t
                
                ;
               
                }

来自CODE的代码片
SharedPreferencesUtils.java

5.我们来测试一下，修改MainAcitvity.java中的代码

 
           <a target=_blank id="L1" href="http://blog.youkuaiyun.com/nugongahou110/article/details/46913461#L1" rel="#L1" style="color: rgb(102, 102, 102); text-decoration: none;">  1</a>
<a target=_blank id="L2" href="http://blog.youkuaiyun.com/nugongahou110/article/details/46913461#L2" rel="#L2" style="color: rgb(102, 102, 102); text-decoration: none;">  2</a>
<a target=_blank id="L3" href="http://blog.youkuaiyun.com/nugongahou110/article/details/46913461#L3" rel="#L3" style="color: rgb(102, 102, 102); text-decoration: none;">  3</a>
<a target=_blank id="L4" href="http://blog.youkuaiyun.com/nugongahou110/article/details/46913461#L4" rel="#L4" style="color: rgb(102, 102, 102); text-decoration: none;">  4</a>
<a target=_blank id="L5" href="http://blog.youkuaiyun.com/nugongahou110/article/details/46913461#L5" rel="#L5" style="color: rgb(102, 102, 102); text-decoration: none;">  5</a>
<a target=_blank id="L6" href="http://blog.youkuaiyun.com/nugongahou110/article/details/46913461#L6" rel="#L6" style="color: rgb(102, 102, 102); text-decoration: none;">  6</a>
<a target=_blank id="L7" href="http://blog.youkuaiyun.com/nugongahou110/article/details/46913461#L7" rel="#L7" style="color: rgb(102, 102, 102); text-decoration: none;">  7</a>
<a target=_blank id="L8" href="http://blog.youkuaiyun.com/nugongahou110/article/details/46913461#L8" rel="#L8" style="color: rgb(102, 102, 102); text-decoration: none;">  8</a>
<a target=_blank id="L9" href="http://blog.youkuaiyun.com/nugongahou110/article/details/46913461#L9" rel="#L9" style="color: rgb(102, 102, 102); text-decoration: none;">  9</a>
<a target=_blank id="L10" href="http://blog.youkuaiyun.com/nugongahou110/article/details/46913461#L10" rel="#L10" style="color: rgb(102, 102, 102); text-decoration: none;"> 10</a>
<a target=_blank id="L11" href="http://blog.youkuaiyun.com/nugongahou110/article/details/46913461#L11" rel="#L11" style="color: rgb(102, 102, 102); text-decoration: none;"> 11</a>
<a target=_blank id="L12" href="http://blog.youkuaiyun.com/nugongahou110/article/details/46913461#L12" rel="#L12" style="color: rgb(102, 102, 102); text-decoration: none;"> 12</a>
<a target=_blank id="L13" href="http://blog.youkuaiyun.com/nugongahou110/article/details/46913461#L13" rel="#L13" style="color: rgb(102, 102, 102); text-decoration: none;"> 13</a>
<a target=_blank id="L14" href="http://blog.youkuaiyun.com/nugongahou110/article/details/46913461#L14" rel="#L14" style="color: rgb(102, 102, 102); text-decoration: none;"> 14</a> 
               
                 public 
                 
                 class 
                 
                 MainActivity 
                 
                 extends 
                 
                 Activity 
                 
                 {
                
                 @Override
                
                 protected 
                 
                 void 
                 
                 onCreate
                 
                 (
                 
                 Bundle 
                 
                 savedInstanceState
                 
                 ) 
                 
                 {
                
                 super
                 
                 .
                 
                 onCreate
                 
                 (
                 
                 savedInstanceState
                 
                 );
                
                 setContentView
                 
                 (
                 
                 R
                 
                 .
                 
                 layout
                 
                 .
                 
                 activity_main
                 
                 );
                
                 //实例化一个Person实例，这是我们想要存储到SharedPreferences中的对象
                
                 Person 
                 
                 p 
                 
                 = 
                 
                 new 
                 
                 Person
                 
                 (
                 
                 "zhangsan"
                 
                 ,
                 
                 23
                 
                 ,
                 
                 175.0f
                 
                 ,
                 
                 false
                 
                 ,
                 
                 "001"
                 
                 );
                
                 //将p存储到SharedPreferences的“zhangqi”名下
                
                 SharedPreferencesUtils
                 
                 .
                 
                 getInstance
                 
                 (
                 
                 this
                 
                 ).
                 
                 putObjectToShare
                 
                 (
                 
                 "zhangqi"
                 
                 ,
                 
                 p
                 
                 );;
                
                 //从SharedPreferences的“zhangqi”名下取出之前存储过的Person实例
                
                 Person 
                 
                 savedPerson 
                 
                 = 
                 
                 SharedPreferencesUtils
                 
                 .
                 
                 getInstance
                 
                 (
                 
                 this
                 
                 ).
                 
                 getObjectFromShare
                 
                 (
                 
                 "zhangqi"
                 
                 ,
                 
                 Person
                 
                 .
                 
                 class
                 
                 );
                
                 Log
                 
                 .
                 
                 e
                 
                 (
                 
                 "zhangqi"
                 
                 ,
                 
                 ""
                 
                 +
                 
                 savedPerson
                 
                 .
                 
                 toString
                 
                 ());
                
                 }
                
                 }