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

我已经阅读了上面所有的答案。这都是正确的,但我找到了一个更简单的解决方案如下:

Saving String List in shared-preference>> public static void setSharedPreferenceStringList(Context pContext, String pKey, List<String> pData) { SharedPreferences.Editor editor = pContext.getSharedPreferences(Constants.APP_PREFS, Activity.MODE_PRIVATE).edit(); editor.putInt(pKey + "size", pData.size()); editor.commit(); for (int i = 0; i < pData.size(); i++) { SharedPreferences.Editor editor1 = pContext.getSharedPreferences(Constants.APP_PREFS, Activity.MODE_PRIVATE).edit(); editor1.putString(pKey + i, (pData.get(i))); editor1.commit(); } } and for getting String List from Shared-preference>> public static List<String> getSharedPreferenceStringList(Context pContext, String pKey) { int size = pContext.getSharedPreferences(Constants.APP_PREFS, Activity.MODE_PRIVATE).getInt(pKey + "size", 0); List<String> list = new ArrayList<>(); for (int i = 0; i < size; i++) { list.add(pContext.getSharedPreferences(Constants.APP_PREFS, Activity.MODE_PRIVATE).getString(pKey + i, "")); } return list; }

这里的常数。APP_PREFS是要打开的文件的名称;不能包含路径分隔符。

其他回答

最好的方法是使用GSON转换为JSOn字符串并保存此字符串到SharedPreference。 我还使用这种方式缓存响应。

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…

使用Kotlin,对于简单的数组和列表,你可以这样做:

class MyPrefs(context: Context) {
    val prefs = context.getSharedPreferences("x.y.z.PREFS_FILENAME", 0)
    var listOfFloats: List<Float>
        get() = prefs.getString("listOfFloats", "").split(",").map { it.toFloat() }
        set(value) = prefs.edit().putString("listOfFloats", value.joinToString(",")).apply()
}

然后轻松访问首选项:

MyPrefs(context).listOfFloats = ....
val list = MyPrefs(context).listOfFloats

以防有人需要保存列表的列表,即list < list < String > >。我是这样做的:

序列化

Gson gson = new Gson();
// Save the size of the array
sharedPreferencesEditor.putInt("ArraySize", myArray.size());

for (int i=0; i<myArray.size(); i++) {
  String key = "Array"+i;
  String json = gson.toJson(myArray.get(i));
  sharedPreferencesEditor.putString(key, json);
}

sharedPreferencesEditor.commit();

反序列化

// Get the size of the array to be deserialized. In my case, the default number should be 3
int arraySize = sharedPreferences.getInt("ArraySize",3);

myArray = new ArrayList<List<String>>();

for (int i=0; i<arraySize; i++) {
  String key = "Array"+i;
  String json = sharedPreferences.getString(key, null);
  List<String> arrayTemp= gson.fromJson(json, List.class);
  myArray.add(arrayTemp);
}

// My array may also include components with empty strings. 
// Gson makes them null values and it is not possible 
// to deserialize them as empty strings. 
// The following takes care of that:

for (int i=0; i<myArray.size();i++) {
   if (myArray.get(i) == null) {
      List<String> emptyComponent = new ArrayList<String>() {
         { add(""); }
      };
      myArray.set(i,emptyComponent);
   }
}

别忘了实现Serializable:

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

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