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。

1. 通过context.getsharedpreferences()获取的sharedpreferences是一个单例
   
2. 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

sharedpreference userpreferences = 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。

import android.content.sharedpreferences;
import android.support.annotation.nullable;

import java.util.map;
import java.util.set;

/**
 * sharedpreferences 包装类
 * created by wittytutu on 17-3-29.
 */

public class preferenceswrapper implements sharedpreferences {

  protected sharedpreferences mpreferences;

  public preferenceswrapper(sharedpreferences preferences) {
    mpreferences = preferences;
  }

  @override
  public map getall() {
    return mpreferences.getall();
  }

  @nullable
  @override
  public string getstring(string key, @nullable string defvalue) {
    return mpreferences.getstring(key, defvalue);
  }

  @nullable
  @override
  public set getstringset(string key, @nullable set defvalues) {
    return mpreferences.getstringset(key, defvalues);
  }

  @override
  public int getint(string key, int defvalue) {
    return mpreferences.getint(key, defvalue);
  }

  @override
  public long getlong(string key, long defvalue) {
    return mpreferences.getlong(key, defvalue);
  }

  @override
  public float getfloat(string key, float defvalue) {
    return mpreferences.getfloat(key, defvalue);
  }

  @override
  public boolean getboolean(string key, boolean defvalue) {
    return mpreferences.getboolean(key, defvalue);
  }

  @override
  public boolean contains(string key) {
    return mpreferences.contains(key);
  }

  @override
  public editorwrapper edit() {
    return new editorwrapper(mpreferences.edit());
  }

  @override
  public void registeronsharedpreferencechangelistener(onsharedpreferencechangelistener listener) {
    mpreferences.registeronsharedpreferencechangelistener(listener);
  }

  @override
  public void unregisteronsharedpreferencechangelistener(onsharedpreferencechangelistener listener) {
    mpreferences.unregisteronsharedpreferencechangelistener(listener);
  }

  public static class editorwrapper implements editor {
    protected editor meditor;

    public editorwrapper(editor editor) {
      meditor = editor;
    }

    @override
    public editorwrapper putstring(string key, @nullable string value) {
      meditor.putstring(key, value);
      return this;
    }

    @override
    public editorwrapper putstringset(string key, @nullable set values) {
      meditor.putstringset(key, values);
      return this;
    }

    @override
    public editorwrapper putint(string key, int value) {
      meditor.putint(key, value);
      return this;
    }

    @override
    public editorwrapper putlong(string key, long value) {
      meditor.putlong(key, value);
      return this;
    }

    @override
    public editorwrapper putfloat(string key, float value) {
      meditor.putfloat(key, value);
      return this;
    }

    @override
    public editorwrapper putboolean(string key, boolean value) {
      meditor.putboolean(key, value);
      return this;
    }

    @override
    public editorwrapper remove(string key) {
      meditor.remove(key);
      return this;
    }

    @override
    public editorwrapper clear() {
      meditor.clear();
      return this;
    }

    @override
    public boolean commit() {
      return meditor.commit();
    }

    @override
    public void apply() {
      meditor.apply();
    }
  }
}

接下来的使用就简单了

public class userinfopreferences extends preferenceswrapper {
  private static final string name = "userinfo";

  public static final key_id = "id"
  public static final key_name = "name";
  public static final key_head = "head";
  public static final key_sex = "sex";

  private static volatile userinfopreferences mpreferences;

  public static userinfopreferences getinstance(context context){
    if(mpreferences == null) {
      synchronized (userinfopreferences.class){
        if(mpreferences == null) {
          sharedpreferences preferences = context.getapplicationctontext().getshaedpreferences(name, context.mode_private);
          mpreferences = new userinfopreferences(preferences);
        }
      }
    }
    return mpreferences;
  }

  public userinfopreferences(sharedpreferences preferences) {
    super(preferences);
  }

  // 获取用户信息
  public userinfo getuserinfo(){
    string id = mpreferences.getstring(key_id, "");
    string name = mpreferences.getstring(key_name, "");
    string head = mpreferences.getstring(key_head, "");
    return new userinfo(id, name, head);
  }

  @override
  public editor edit(){
    return new editor(mpreferences.edit());
  }

  public static class editor extends editorwrapper {

    public editor(sharedpreferences.editor editor) {
      super(editor);
    }

    // 保存用户信息
    public editor putuserinfo(string id, string name, string head) {

      meditor.putstring(key_id, id)
          .putstring(key_ame, name)
          .putstring(key_head, head);
      return this;
    }

    // 清空用户信息
    public editor clearuserinfo() {

      meditor.remove(key_id)
          .remove(key_name)
          .remove(key_head);
      return this;
    }
  }
}

调用即方便扩展，也保留了原有方法。

userinfopreferences preferences = userinfopreferences.getinstance(context);
preferences.edit()
  .clearuserinfo()
  .putuserinfo("myid", "myname", "myhead")
  .putint(key_sex, 0)
  .commit();
userinfo userinfo = preferences.getuserinfo();
int sex = preferences.getint(key_sex, 0);

感谢阅读，希望能帮助到大家，谢谢大家对本站的支持！