SharedPreferences的apply和commit两种

关于SharedPreferences我们在Android开发中经常使用到，SharedPreferences有apply和commit两种提交方式：

/**
     * 保存到本地SharedPreferences的boolean数据
     *
     * @param context 传入的上下文对象
     * @param key     得到数据的标识
     * @param value   如果获得不到的默认值
     */
    public static void putPreBoolean(Context context, String key, boolean value) {
        if (pre==null){
            pre = context.getSharedPreferences(CONFIG_NAME, Context.MODE_PRIVATE);
        }
        pre.edit().putBoolean(key, value).commit();
    }

/**
     * 保存到本地SharedPreferences的boolean数据
     *
     * @param context 传入的上下文对象
     * @param key     得到数据的标识
     * @param value   如果获得不到的默认值
     */
    public static void putPreBoolean(Context context, String key, boolean value) {
        if (pre==null){
            pre = context.getSharedPreferences(CONFIG_NAME, Context.MODE_PRIVATE);
        }
        pre.edit().putBoolean(key, value).apply();
    }

我们查看一下官方给的注释：

/**
         * Commit your preferences changes back from this Editor to the
         * {@link SharedPreferences} object it is editing.  This atomically
         * performs the requested modifications, replacing whatever is currently
         * in the SharedPreferences.
         *
         * <p>Note that when two editors are modifying preferences at the same
         * time, the last one to call commit wins.
         *
         * <p>If you don't care about the return value and you're
         * using this from your application's main thread, consider
         * using {@link #apply} instead.
         *
         * @return Returns true if the new values were successfully written
         * to persistent storage.
         */
        boolean commit();

        /**
         * Commit your preferences changes back from this Editor to the
         * {@link SharedPreferences} object it is editing.  This atomically
         * performs the requested modifications, replacing whatever is currently
         * in the SharedPreferences.
         *
         * <p>Note that when two editors are modifying preferences at the same
         * time, the last one to call apply wins.
         *
         * <p>Unlike {@link #commit}, which writes its preferences out
         * to persistent storage synchronously, {@link #apply}
         * commits its changes to the in-memory
         * {@link SharedPreferences} immediately but starts an
         * asynchronous commit to disk and you won't be notified of
         * any failures.  If another editor on this
         * {@link SharedPreferences} does a regular {@link #commit}
         * while a {@link #apply} is still outstanding, the
         * {@link #commit} will block until all async commits are
         * completed as well as the commit itself.
         *
         * <p>As {@link SharedPreferences} instances are singletons within
         * a process, it's safe to replace any instance of {@link #commit} with
         * {@link #apply} if you were already ignoring the return value.
         *
         * <p>You don't need to worry about Android component
         * lifecycles and their interaction with <code>apply()</code>
         * writing to disk.  The framework makes sure in-flight disk
         * writes from <code>apply()</code> complete before switching
         * states.
         *
         * <p class='note'>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 <code>apply()</code>, you can simply call
         * {@link #commit} from <code>apply()</code>.
         */
        void apply();

大概区别如下：
（1）apply是无返回值的，而commit是有返回值，所以使用apply提交之后，无法判定是否提交成功，而commit方式可以返回是否提交成功的布尔值，所以在需要得到返回值的情况下建议使用commit方式
（2）apply操作是一个原子性的操作，是先把数据提交到内存中，然后再通过异步任务提交到硬件磁盘上。而commit是个同步操作，直接把数据提交到硬件磁盘上。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。

总结：

在开发中如果我们需要返回值的情况（一般不需要），那就选用commit方式。其他情况，建议选用效率比较高的apply方式。
注意：SharedPreferences能够存储的数据类型：String、Int、Long、Float、Boolean、Set<String>