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?


当前回答

嘿,朋友们,我没有使用Gson库就得到了上述问题的解决方案。我在这里发布源代码。

1.变量声明,即

  SharedPreferences shared;
  ArrayList<String> arrPackage;

2.变量初始化,即

 shared = getSharedPreferences("App_settings", MODE_PRIVATE);
 // add values for your ArrayList any where...
 arrPackage = new ArrayList<>();

3.使用packagesharedPreferences()将值存储到sharedPreference:

 private void packagesharedPreferences() {
   SharedPreferences.Editor editor = shared.edit();
   Set<String> set = new HashSet<String>();
   set.addAll(arrPackage);
   editor.putStringSet("DATE_LIST", set);
   editor.apply();
   Log.d("storesharedPreferences",""+set);
 }

4.使用retriveSharedValue()检索sharedPreference的值:

 private void retriveSharedValue() {
   Set<String> set = shared.getStringSet("DATE_LIST", null);
   arrPackage.addAll(set);
   Log.d("retrivesharedPreferences",""+set);
 }

我希望这对你有帮助…

其他回答

在API 11之后,SharedPreferences Editor接受set。您可以将List转换为HashSet或类似的东西,并像这样存储它。当你把它读回来时,把它转换成一个数组列表,如果需要的话对它排序,你就可以开始了。

//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();

你也可以序列化你的数组列表,然后将它保存/读取到SharedPreferences。解决方案如下:

编辑: 下面是将ArrayList作为一个序列化对象保存到SharedPreferences的解决方案,然后从SharedPreferences中读取它。

因为API只支持在SharedPreferences中存储和检索字符串(在API 11之后,它更简单),我们必须序列化和反序列化ArrayList对象,它将任务列表变成一个字符串。

在TaskManagerApplication类的addTask()方法中,我们必须获取共享首选项的实例,然后使用putString()方法存储序列化的ArrayList:

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();
}

类似地,我们必须从onCreate()方法中的首选项中检索任务列表:

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 Pig项目ObjectSerializer.java中获得ObjectSerializer类

下面的代码是公认的答案,为新手(我)多写几行,例如。说明了如何将set类型对象转换回arrayList,并提供了关于`之前操作的附加指导。putStringSet'和。getstringset '。(谢谢你邪恶)

// shared preferences
   private SharedPreferences preferences;
   private SharedPreferences.Editor nsuserdefaults;

// setup persistent data
        preferences = this.getSharedPreferences("MyPreferences", MainActivity.MODE_PRIVATE);
        nsuserdefaults = preferences.edit();

        arrayOfMemberUrlsUserIsFollowing = new ArrayList<String>();
        //Retrieve followers from sharedPreferences
        Set<String> set = preferences.getStringSet("following", null);

        if (set == null) {
            // lazy instantiate array
            arrayOfMemberUrlsUserIsFollowing = new ArrayList<String>();
        } else {
            // there is data from previous run
            arrayOfMemberUrlsUserIsFollowing = new ArrayList<>(set);
        }

// convert arraylist to set, and save arrayOfMemberUrlsUserIsFollowing to nsuserdefaults
                Set<String> set = new HashSet<String>();
                set.addAll(arrayOfMemberUrlsUserIsFollowing);
                nsuserdefaults.putStringSet("following", set);
                nsuserdefaults.commit();

嘿,朋友们,我没有使用Gson库就得到了上述问题的解决方案。我在这里发布源代码。

1.变量声明,即

  SharedPreferences shared;
  ArrayList<String> arrPackage;

2.变量初始化,即

 shared = getSharedPreferences("App_settings", MODE_PRIVATE);
 // add values for your ArrayList any where...
 arrPackage = new ArrayList<>();

3.使用packagesharedPreferences()将值存储到sharedPreference:

 private void packagesharedPreferences() {
   SharedPreferences.Editor editor = shared.edit();
   Set<String> set = new HashSet<String>();
   set.addAll(arrPackage);
   editor.putStringSet("DATE_LIST", set);
   editor.apply();
   Log.d("storesharedPreferences",""+set);
 }

4.使用retriveSharedValue()检索sharedPreference的值:

 private void retriveSharedValue() {
   Set<String> set = shared.getStringSet("DATE_LIST", null);
   arrPackage.addAll(set);
   Log.d("retrivesharedPreferences",""+set);
 }

我希望这对你有帮助…

Android sharedpreferences允许您将基本类型(Boolean, Float, Int, Long, String和StringSet,自API11以来可用)作为xml文件保存在内存中。

任何解决方案的关键思想都是将数据转换为这些基本类型之一。

我个人喜欢将my list转换为json格式,然后将其保存为SharedPreferences值中的字符串。

为了使用我的解决方案,你必须添加谷歌gsonlib。

在gradle中只需添加以下依赖项(请使用谷歌的最新版本):

compile 'com.google.code.gson:gson:2.6.2'

保存数据(HttpParam是你的对象):

List<HttpParam> httpParamList = "**get your list**"
String httpParamJSONList = new Gson().toJson(httpParamList);

SharedPreferences prefs = getSharedPreferences(**"your_prefes_key"**, Context.MODE_PRIVATE);
SharedPreferences.Editor editor = prefs.edit();
editor.putString(**"your_prefes_key"**, httpParamJSONList);

editor.apply();

检索数据(HttpParam是你的对象):

SharedPreferences prefs = getSharedPreferences(**"your_prefes_key"**, Context.MODE_PRIVATE);
String httpParamJSONList = prefs.getString(**"your_prefes_key"**, ""); 

List<HttpParam> httpParamList =  
new Gson().fromJson(httpParamJSONList, new TypeToken<List<HttpParam>>() {
            }.getType());

别忘了实现Serializable:

Class dataBean implements Serializable{
 public String name;
}
ArrayList<dataBean> dataBeanArrayList = new ArrayList();

https://stackoverflow.com/a/7635154/4639974