【Android】数据存储（一） SharedPreferences详解

0.22 2016.04.29 00:13:33 字数 919 阅读 13345

SharedPreferences介绍

在Android开发中，经常需要将少量简单类型数据保存在本地，如：用户设置。这些需要保存的数据可能一两个字符串，像这样的数据一般选择使用SharedPreferences来保存。

SharedPreferences：一个轻量级的存储类，特别适合用于保存软件配置参数。（是用xml文件存放数据，文件存放在/data/data/<package name>/shared_prefs目录下）

SharedPreferences可以保存的数据类型有：int、boolean、float、long、String、StringSet。

使用SharedPreferences存储和读取数据的步骤

存储数据

保存数据一般分为四个步骤：

使用Activity类的getSharedPreferences方法获得SharedPreferences对象；
使用SharedPreferences接口的edit获得SharedPreferences.Editor对象；
通过SharedPreferences.Editor接口的putXXX方法保存key-value对；
通过过SharedPreferences.Editor接口的commit方法保存key-value对。

读取数据

读取数据一般分为两个步骤：

使用Activity类的getSharedPreferences方法获得SharedPreferences对象；
通过SharedPreferences对象的getXXX方法获取数据；

用到的方法

获取SharedPreferences对象
（根据name查找SharedPreferences，若已经存在则获取，若不存在则创建一个新的）

public abstract SharedPreferences getSharedPreferences (String name, int mode)

参数
name：命名
mode：模式，包括
MODE_PRIVATE（只能被自己的应用程序访问）
MODE_WORLD_READABLE（除了自己访问外还可以被其它应该程序读取）
MODE_WORLD_WRITEABLE（除了自己访问外还可以被其它应该程序读取和写入）

若该Activity只需要创建一个SharedPreferences对象的时候，可以使用getPreferences方法，不需要为SharedPreferences对象命名，只要传入参数mode即可

public SharedPreferences getPreferences (int mode)

获取Editor对象（由SharedPreferences对象调用）

abstract SharedPreferences.Editor edit()

写入数据（由Editor对象调用）

//写入boolean类型的数据
abstract SharedPreferences.Editor   putBoolean(String key, boolean value)
//写入float类型的数据
abstract SharedPreferences.Editor   putFloat(String key, float value)
//写入int类型的数据
abstract SharedPreferences.Editor   putInt(String key, int value)
//写入long类型的数据
abstract SharedPreferences.Editor   putLong(String key, long value)
//写入String类型的数据
abstract SharedPreferences.Editor   putString(String key, String value)
//写入Set<String>类型的数据
abstract SharedPreferences.Editor   putStringSet(String key, Set<String> values)

参数
key：指定数据对应的key
value：指定的值

移除指定key的数据（由Editor对象调用）

abstract SharedPreferences.Editor   remove(String key)

参数
key：指定数据的key

清空数据（由Editor对象调用）

abstract SharedPreferences.Editor   clear()

提交数据（由Editor对象调用）

abstract boolean    commit()

读取数据（由SharedPreferences对象调用）

//读取所有数据
abstract Map<String, ?> getAll()
//读取的数据为boolean类型
abstract boolean    getBoolean(String key, boolean defValue)
//读取的数据为float类型
abstract float  getFloat(String key, float defValue)
//读取的数据为int类型
abstract int    getInt(String key, int defValue)
//读取的数据为long类型
abstract long   getLong(String key, long defValue)
//读取的数据为String类型
abstract String getString(String key, String defValue)
//读取的数据为Set<String>类型
abstract Set<String>    getStringSet(String key, Set<String> defValues)

参数
key：指定数据的key
defValue：当读取不到指定的数据时，使用的默认值defValue

SharedPreferences的使用

看烦了这些方法？别着急，，，代码来了

    /**
     * 保存用户信息
     */
    private void saveUserInfo(){
        SharedPreferences userInfo = getSharedPreferences(PREFS_NAME, MODE_PRIVATE);
        SharedPreferences.Editor editor = userInfo.edit();//获取Editor
        //得到Editor后，写入需要保存的数据
        editor.putString("username", "一只猫的涵养");
        editor.putInt("age", 20);
        editor.commit();//提交修改
        Log.i(TAG, "保存用户信息成功");
    }
    /**
     * 读取用户信息
     */
    private void getUserInfo(){
        SharedPreferences userInfo = getSharedPreferences(PREFS_NAME, MODE_PRIVATE);
        String username = userInfo.getString("username", null);//读取username
        int age = userInfo.getInt("age", 0);//读取age
        Log.i(TAG, "读取用户信息");
        Log.i(TAG, "username:" + username + "， age:" + age);
    }
    /**
     * 移除年龄信数据
     */
    private void removeUserInfo(){
        SharedPreferences userInfo = getSharedPreferences(PREFS_NAME, MODE_PRIVATE);
        SharedPreferences.Editor editor = userInfo.edit();//获取Editor
        editor.remove("age");
        editor.commit();
        Log.i(TAG, "移除年龄数据");
    }
<span class="token comment">/**
 * 清空数据
 */</span>
<span class="token keyword">private</span> <span class="token keyword">void</span> <span class="token function">clearUserInfo</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
    <span class="token class-name">SharedPreferences</span> userInfo <span class="token operator">=</span> <span class="token function">getSharedPreferences</span><span class="token punctuation">(</span>PREFS_NAME<span class="token punctuation">,</span> MODE_PRIVATE<span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token class-name">SharedPreferences</span><span class="token punctuation">.</span><span class="token class-name">Editor</span> editor <span class="token operator">=</span> userInfo<span class="token punctuation">.</span><span class="token function">edit</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token comment">//获取Editor</span>
    editor<span class="token punctuation">.</span><span class="token function">clear</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    editor<span class="token punctuation">.</span><span class="token function">commit</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token class-name">Log</span><span class="token punctuation">.</span><span class="token function">i</span><span class="token punctuation">(</span>TAG<span class="token punctuation">,</span> <span class="token string">"清空数据"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>

这里将SharedPreferences简单的用法都列举了出来。

api中还注册和注销SharedPreferences被编辑时的监听

        SharedPreferences.OnSharedPreferenceChangeListener changeListener = new OnSharedPreferenceChangeListener() {
            @Override
            public void onSharedPreferenceChanged(SharedPreferences preferences, String key) {
                //preferences被 编辑的SharedPreferences实例
                //该SharedPreferences中被编辑的条目所对应的key
            }
        };
        //userInfo注册监听事件
        userInfo.registerOnSharedPreferenceChangeListener(changeListener);
        //userInfo注销监听事件
        userInfo.unregisterOnSharedPreferenceChangeListener(changeListener);

性能

ShredPreferences是单例对象，第一次打开后，之后获取都无需创建，速度很快。
当第一次获取数据后，数据会被加载到一个缓存的Map中，之后的读取都会非常快。
当由于是XML<->Map的存储方式，所以，数据越大，操作越慢，get、commit、apply、remove、clear都会受影响，所以尽量把数据按功能拆分成若干份。

Tips

tip 1
这里的用到的：

getSharedPreferences (String name, int mode)

getPreferences (int mode)

MODE_PRIVATE

都是在Acitivty中执行的。若不在Activity中，请使用

context.getSharedPreferences (String name, int mode)

context.getPreferences (int mode)

Conetxt.MODE_PRIVATE

tip 2
所保存的SharedPreferences数据将一直存在，除非被覆盖、移除、清空或文件被删除。
（SharedPreferences保存的数据会随着应用的卸载而被删除）
tip 3
同时执行这两句代码的时候，第一行代码所写的内容会被第二行代码取代。

editor.putInt("age", 20);
//覆盖key为age的数据，得到的结果：age = 32
editor.putInt("age", 32);

editor.putString("age", "20");
//覆盖key为age的数据，得到的结果：age = 32 (int类型)
editor.putInt("age", 32);

tip 4
执行以下代码会出现异常。
（指定key所保存的类型和读取时的类型不同）

editor.putInt("age", 32);//保存为int类型
String age = userInfo.getString("age", "null");//读取时为String类型，出现异常

tip 5
在这些动作之后，记得commit

editor.putInt("age", 20);//写入操作
editor.remove("age");   //移除操作
editor.clear();     //清空操作
editor.commit();//记得commit

附：源代码

import android.app.Activity;
import android.content.Context;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.util.Log;
/**
 * SharedPreferences用法 测试Activity
 * @author Gavin
 *
 */
public class MainActivity extends Activity {
    private static final String TAG = "SharedPreferencesTest";
    /**
     * 保存数据SharedPreferences文件的名字
     */
    private final String PREFS_NAME = "MyPrefsFile";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        saveUserInfo();
        getUserInfo();
        removeUserInfo();
        getUserInfo();
        clearUserInfo();
        getUserInfo();
    }
<span class="token comment">/**
 * 保存用户信息
 */</span>
<span class="token keyword">private</span> <span class="token keyword">void</span> <span class="token function">saveUserInfo</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
    <span class="token class-name">SharedPreferences</span> userInfo <span class="token operator">=</span> <span class="token function">getSharedPreferences</span><span class="token punctuation">(</span>PREFS_NAME<span class="token punctuation">,</span> MODE_PRIVATE<span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token class-name">SharedPreferences</span><span class="token punctuation">.</span><span class="token class-name">OnSharedPreferenceChangeListener</span> changeListener <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">OnSharedPreferenceChangeListener</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
        
        <span class="token annotation punctuation">@Override</span>
        <span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">onSharedPreferenceChanged</span><span class="token punctuation">(</span><span class="token class-name">SharedPreferences</span> preferences<span class="token punctuation">,</span> <span class="token class-name">String</span> key<span class="token punctuation">)</span> <span class="token punctuation">{</span>
            <span class="token comment">//preferences被 编辑的SharedPreferences实例</span>
            <span class="token comment">//该SharedPreferences中被编辑的条目所对应的key</span>
        <span class="token punctuation">}</span>
    <span class="token punctuation">}</span><span class="token punctuation">;</span>
    <span class="token comment">//userInfo注册监听事件</span>
    userInfo<span class="token punctuation">.</span><span class="token function">registerOnSharedPreferenceChangeListener</span><span class="token punctuation">(</span>changeListener<span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token class-name">SharedPreferences</span><span class="token punctuation">.</span><span class="token class-name">Editor</span> editor <span class="token operator">=</span> userInfo<span class="token punctuation">.</span><span class="token function">edit</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token comment">//获取Editor</span>
    <span class="token comment">//得到Editor后，写入需要保存的数据</span>
    editor<span class="token punctuation">.</span><span class="token function">putString</span><span class="token punctuation">(</span><span class="token string">"username"</span><span class="token punctuation">,</span> <span class="token string">"一只猫的涵养"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    editor<span class="token punctuation">.</span><span class="token function">putInt</span><span class="token punctuation">(</span><span class="token string">"age"</span><span class="token punctuation">,</span> <span class="token number">20</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    editor<span class="token punctuation">.</span><span class="token function">commit</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token comment">//提交修改</span>
    <span class="token class-name">Log</span><span class="token punctuation">.</span><span class="token function">i</span><span class="token punctuation">(</span>TAG<span class="token punctuation">,</span> <span class="token string">"保存用户信息成功"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>

<span class="token comment">/**
 * 读取用户信息
 */</span>
<span class="token keyword">private</span> <span class="token keyword">void</span> <span class="token function">getUserInfo</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
    <span class="token class-name">SharedPreferences</span> userInfo <span class="token operator">=</span> <span class="token function">getSharedPreferences</span><span class="token punctuation">(</span>PREFS_NAME<span class="token punctuation">,</span> MODE_PRIVATE<span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token class-name">String</span> username <span class="token operator">=</span> userInfo<span class="token punctuation">.</span><span class="token function">getString</span><span class="token punctuation">(</span><span class="token string">"username"</span><span class="token punctuation">,</span> <span class="token keyword">null</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token comment">//读取username</span>
    <span class="token keyword">int</span> age <span class="token operator">=</span> userInfo<span class="token punctuation">.</span><span class="token function">getInt</span><span class="token punctuation">(</span><span class="token string">"age"</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token comment">//读取age</span>
    <span class="token class-name">Log</span><span class="token punctuation">.</span><span class="token function">i</span><span class="token punctuation">(</span>TAG<span class="token punctuation">,</span> <span class="token string">"读取用户信息"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token class-name">Log</span><span class="token punctuation">.</span><span class="token function">i</span><span class="token punctuation">(</span>TAG<span class="token punctuation">,</span> <span class="token string">"username:"</span> <span class="token operator">+</span> username <span class="token operator">+</span> <span class="token string">"， age:"</span> <span class="token operator">+</span> age<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>

<span class="token comment">/**
 * 移除年龄信数据
 */</span>
<span class="token keyword">private</span> <span class="token keyword">void</span> <span class="token function">removeUserInfo</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
    <span class="token class-name">SharedPreferences</span> userInfo <span class="token operator">=</span> <span class="token function">getSharedPreferences</span><span class="token punctuation">(</span>PREFS_NAME<span class="token punctuation">,</span> MODE_PRIVATE<span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token class-name">SharedPreferences</span><span class="token punctuation">.</span><span class="token class-name">Editor</span> editor <span class="token operator">=</span> userInfo<span class="token punctuation">.</span><span class="token function">edit</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token comment">//获取Editor</span>
    editor<span class="token punctuation">.</span><span class="token function">remove</span><span class="token punctuation">(</span><span class="token string">"age"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    editor<span class="token punctuation">.</span><span class="token function">commit</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token class-name">Log</span><span class="token punctuation">.</span><span class="token function">i</span><span class="token punctuation">(</span>TAG<span class="token punctuation">,</span> <span class="token string">"移除年龄数据"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>

<span class="token comment">/**
 * 清空数据
 */</span>
<span class="token keyword">private</span> <span class="token keyword">void</span> <span class="token function">clearUserInfo</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
    <span class="token class-name">SharedPreferences</span> userInfo <span class="token operator">=</span> <span class="token function">getSharedPreferences</span><span class="token punctuation">(</span>PREFS_NAME<span class="token punctuation">,</span> MODE_PRIVATE<span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token class-name">SharedPreferences</span><span class="token punctuation">.</span><span class="token class-name">Editor</span> editor <span class="token operator">=</span> userInfo<span class="token punctuation">.</span><span class="token function">edit</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token comment">//获取Editor</span>
    editor<span class="token punctuation">.</span><span class="token function">clear</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    editor<span class="token punctuation">.</span><span class="token function">commit</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token class-name">Log</span><span class="token punctuation">.</span><span class="token function">i</span><span class="token punctuation">(</span>TAG<span class="token punctuation">,</span> <span class="token string">"清空数据"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>

}

得到log：

log

参考：
google开发者文档

Nydia~

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