ArrayList中保存到共享preferences [英] Save ArrayList to SharedPreferences

问题描述

我有一个的ArrayList 自定义对象。每个自定义对象包含了各种字符串和数字。予需要该阵列即使用户离开活动，然后想回来在以后的时间，要坚持，但是我不需要后可用的应用程序已经完全关闭的阵列。我节省了很多其他物体的这种方式使用共享preferences ，但我无法弄清楚如何拯救我的整个数组这种方式。这可能吗？也许共享preferences 不是办法去了解呢？是否有一个更简单的方法？

I have an ArrayList with custom objects. Each custom object contains a variety of strings and numbers. I need the array to stick around even if the user leaves the activity and then wants to come back at a later time, however I don't need the array available after the application has been closed completely. I save a lot of other objects this way by using the SharedPreferences but I can't figure out how to save my entire array this way. Is this possible? Maybe SharedPreferences isn't the way to go about this? Is there a simpler method?

推荐答案

11 API共享preferences编辑器接受设置之后。您可以将您的列表到HashSet的或类似的东西，并将其存储这样的。当你读回，将其转换成一个ArrayList，排序，如果需要，你是好去。

After API 11 the SharedPreferences Editor accept Sets. You could convert your List into a HashSet or something similar and store it like that. When your read it back, convert it into an ArrayList, sort it if needed and you're good to go.

//Retrieve the values
Set<String> set = myScores.getStringSet("key", null);

//Set the values
Set<String> set = new HashSet<String>();
set.addAll(listOfExistingScores);
scoreEditor.putStringSet("key", set);
scoreEditor.commit();

---

您也可以序列化的ArrayList，然后保存/从共享preferences读/。下面是解决方案：

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You can also serialize your ArrayList and then save/read it to/from SharedPreferences. Below is the solution:

编辑：确定，下面是解决方案，以节省ArrayList的系列化对象共享preferences，然后从共享preferences阅读

Ok, below is the solution to save ArrayList as serialized object to SharedPreferences and then read it from SharedPreferences.

由于API仅支持存储和检索字符串/从共享preferences的（API 11后，它的简单），我们必须序列化和反序列化ArrayList的对象，它有任务列表转换为字符串。

Because API supports only storing and retrieving of strings to/from SharedPreferences (after API 11, its simpler), we have to serialize and de-serialize the ArrayList object which has the list of tasks into string.

在TaskManagerApplication类的 addTask（）方法，我们得到的共享preference的实例，然后使用存储序列化的ArrayList putString（）方法：

In the addTask() method of the TaskManagerApplication class, we have to get the instance of the shared preference and then store the serialized ArrayList using the putString() method:

public void addTask(Task t) {
        if (null == currentTasks) {
            currentTasks = new ArrayList<task>();
        }
        currentTasks.add(t);

        //save the task list to preference
        SharedPreferences prefs = getSharedPreferences(SHARED_PREFS_FILE, Context.MODE_PRIVATE);
        Editor editor = prefs.edit();
        try {
            editor.putString(TASKS, ObjectSerializer.serialize(currentTasks));
        } catch (IOException e) {
            e.printStackTrace();
        }
        editor.commit();
    }

同样，我们需要检索从的onCreate（）方法preference任务列表：

Similarly we have to retrieve the list of tasks from the preference in the onCreate() method:

public void onCreate() {
        super.onCreate();
        if (null == currentTasks) {
            currentTasks = new ArrayList<task>();
        }

        //      load tasks from preference
        SharedPreferences prefs = getSharedPreferences(SHARED_PREFS_FILE, Context.MODE_PRIVATE);

        try {
            currentTasks = (ArrayList<task>) ObjectSerializer.deserialize(prefs.getString(TASKS, ObjectSerializer.serialize(new ArrayList<task>())));
        } catch (IOException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }

您可以从Apache的猪项目<一大家子ObjectSerializer类href="https://github.com/apache/pig/blob/89c2e8e76c68d0d0abe6a36b4e08ddc56979796f/src/org/apache/pig/impl/util/ObjectSerializer.java">ObjectSerializer.java

You can get ObjectSerializer class from Apache Pig project ObjectSerializer.java

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