SharedPreferencesUtils 工具类 及 SharedPreferences apply和commit方法异同

SharedPreferencesUtils

package com.hhh.android.base.common;

import java.util.Map;

import android.content.Context;
import android.content.SharedPreferences;

/**
 * 此类为工具类
 * 调用setParam就能保存String, Integer, Boolean, Float, Long类型的参数
 * 调用getParam就能获取到保存在手机里面的数据 
 * @author geek_xz
 * @version 1.0
 * @time 2015-8-26 上午9:58:11
 * 
 */
public class SharedPreferencesUtils {
	/** 
     * 保存在手机里面的文件名 
     */  
    private static final String FILE_NAME = "share_date";  
      
      
    /** 
     * 保存数据的方法，我们需要拿到保存数据的具体类型，然后根据类型调用不同的保存方法 
     * @param context 
     * @param key 
     * @param object  
     */  
    public static void setParam(Context context , String key, Object object){  
          
        String type = object.getClass().getSimpleName();  
        SharedPreferences sp = context.getSharedPreferences(FILE_NAME, Context.MODE_PRIVATE);  
        SharedPreferences.Editor editor = sp.edit();  
          
        if("String".equals(type)){  
            editor.putString(key, (String)object);  
        }  
        else if("Integer".equals(type)){  
            editor.putInt(key, (Integer)object);  
        }  
        else if("Boolean".equals(type)){  
            editor.putBoolean(key, (Boolean)object);  
        }  
        else if("Float".equals(type)){  
            editor.putFloat(key, (Float)object);  
        }  
        else if("Long".equals(type)){  
            editor.putLong(key, (Long)object);  
        }  
          
        SharedPreferencesCompat.apply(editor);
    }  
      
      
    /** 
     * 得到保存数据的方法，我们根据默认值得到保存的数据的具体类型，然后调用相对于的方法获取值 
     * @param context 
     * @param key 
     * @param defaultObject 
     * @return 
     */  
    public static Object getParam(Context context , String key, Object defaultObject){  
        String type = defaultObject.getClass().getSimpleName();  
        SharedPreferences sp = context.getSharedPreferences(FILE_NAME, Context.MODE_PRIVATE);  
          
        if("String".equals(type)){  
            return sp.getString(key, (String)defaultObject);  
        }  
        else if("Integer".equals(type)){  
            return sp.getInt(key, (Integer)defaultObject);  
        }  
        else if("Boolean".equals(type)){  
            return sp.getBoolean(key, (Boolean)defaultObject);  
        }  
        else if("Float".equals(type)){  
            return sp.getFloat(key, (Float)defaultObject);  
        }  
        else if("Long".equals(type)){  
            return sp.getLong(key, (Long)defaultObject);  
        }  
          
        return null;  
    }  
    
    /**
	 * 移除某个key值已经对应的值
	 * @param context
	 * @param key
	 */
	public static void remove(Context context, String key)
	{
		SharedPreferences sp = context.getSharedPreferences(FILE_NAME,
				Context.MODE_PRIVATE);
		SharedPreferences.Editor editor = sp.edit();
		editor.remove(key);
		SharedPreferencesCompat.apply(editor);
	}

	/**
	 * 清除所有数据
	 * @param context
	 */
	public static void clear(Context context)
	{
		SharedPreferences sp = context.getSharedPreferences(FILE_NAME,
				Context.MODE_PRIVATE);
		SharedPreferences.Editor editor = sp.edit();
		editor.clear();
		SharedPreferencesCompat.apply(editor);
	}

	/**
	 * 查询某个key是否已经存在
	 * @param context
	 * @param key
	 * @return
	 */
	public static boolean contains(Context context, String key)
	{
		SharedPreferences sp = context.getSharedPreferences(FILE_NAME,
				Context.MODE_PRIVATE);
		return sp.contains(key);
	}

	/**
	 * 返回所有的键值对
	 * 
	 * @param context
	 * @return
	 */
	public static Map getAll(Context context)
	{
		SharedPreferences sp = context.getSharedPreferences(FILE_NAME,
				Context.MODE_PRIVATE);
		return sp.getAll();
	}
}

SharedPreferencesCompat

package com.hhh.android.base.common;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

import android.content.SharedPreferences;

/**
 * 由于editor.commit方法是同步的，并且我们很多时候的commit操作都是UI线程中，毕竟是IO操作，所以尽可能采用异步操作；
 * 所以我们使用apply进行替代，apply异步的进行写入
 * 
 * @author geek_xz
 * @version 1.0
 * @time 2015-8-26 上午10:04:06
 * 
 */
public class SharedPreferencesCompat {
	private static final Method sApplyMethod = findApplyMethod();

	/**
	 * 反射查找apply的方法
	 * 
	 * @return
	 */
	@SuppressWarnings({ "unchecked", "rawtypes" })
	private static Method findApplyMethod() {
		try {
			Class clz = SharedPreferences.Editor.class;
			return clz.getMethod("apply");
		} catch (NoSuchMethodException e) {
		}

		return null;
	}

	/**
	 * 如果找到则使用apply执行，否则使用commit
	 * 
	 * @param editor
	 */
	public static void apply(SharedPreferences.Editor editor) {
		try {
			if (sApplyMethod != null) {
				sApplyMethod.invoke(editor);
				return;
			}
		} catch (IllegalArgumentException e) {
		} catch (IllegalAccessException e) {
		} catch (InvocationTargetException e) {
		}
		editor.commit();
	}
}

在android 中存储数据时经常用SharedPreference, 并且在提交数据时一直用的是Editor的commit方法, 今天无意了看到了系统用了apply,看了方法的介绍, 原来这个方法也是可以提交数据的.

apply方法在官方SDK说明如下：

Commit your preferences changes back from this Editor to the SharedPreferences object it is editing. This atomically performs the requested modifications, replacing whatever is currently in the SharedPreferences.

Note that when two editors are modifying preferences at the same time, the last one to call apply wins.

Unlike commit, which writes its preferences out to persistent storage synchronously, apply commits its changes to the in-memory SharedPreferences immediately but starts an asynchronous commit to disk and you won’t be notified of any failures. If another editor on this SharedPreferences does a regular commit while a apply is still outstanding, the commit will block until all async commits are completed as well as the commit itself.

As SharedPreferences instances are singletons within a process, it’s safe to replace any instance of commit with apply if you were already ignoring the return value.

You don’t need to worry about Android component lifecycles and their interaction with apply() writing to disk. The framework makes sure in-flight disk writes from apply() complete before switching states.

The SharedPreferences.Editor interface isn’t expected to be implemented directly. However, if you previously did implement it and are now getting errors about missing apply(), you can simply call commit from apply().

这两个方法的区别在于： 
1. apply没有返回值而commit返回boolean表明修改是否提交成功 
2. apply是将修改数据原子提交到内存, 而后异步真正提交到硬件磁盘, 而commit是同步的提交到硬件磁盘，因此，在多个并发的提交commit的时候，他们会等待正在处理的commit保存到磁盘后在操作，从而降低了效率。而apply只是原子的提交到内容，后面有调用apply的函数的将会直接覆盖前面的内存数据，这样从一定程度上提高了很多效率。 
3. apply方法不会提示任何失败的提示。 
由于在一个进程中，sharedPreference是单实例，一般不会出现并发冲突，如果对提交的结果不关心的话，建议使用apply，当然需要确保提交成功且有后续操作的话，还是需要用commit的。