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

为什么不把数组列表放在应用程序类上呢?它只有在应用被杀死时才会被销毁,所以,只要应用可用,它就会一直存在。

其他回答

为什么不把数组列表放在应用程序类上呢?它只有在应用被杀死时才会被销毁,所以,只要应用可用,它就会一直存在。

您可以将其转换为Map Object来存储它,然后在检索SharedPreferences时将值更改回ArrayList。

public class VcareSharedPreference {
  private static VcareSharedPreference sharePref = new VcareSharedPreference(); 
  private static SharedPreferences sharedPreferences; 
  private static SharedPreferences.Editor editor;
  private VcareSharedPreference() {
 } 
public static VcareSharedPreference getInstance(Context context) {
    if (sharedPreferences == null) {
        sharedPreferences = context.getSharedPreferences(context.getPackageName(), Activity.MODE_PRIVATE);
        editor = sharedPreferences.edit();
    }
    return sharePref;
 }
public void save(String KEY, String text) {
    editor.putString(KEY, text);
    editor.commit();
}
 public String getValue(String PREFKEY) {
    String text;

    //settings = PreferenceManager.getDefaultSharedPreferences(context);
    text = sharedPreferences.getString(PREFKEY, null);
    return text;
}
public void removeValue(String KEY) {
    editor.remove(KEY);
    editor.commit();
}

public void clearAll() {
    editor.clear();
    editor.commit();
}
public void saveArrayList(String key, ArrayList<ModelWelcome> modelCourses) {
    Gson gson = new Gson();
    String json = gson.toJson(modelCourses);
    editor.putString(key, json);
    editor.apply();
}

public ArrayList<ModelWelcome> getArray(String key) {

    Gson gson = new Gson();
    String json = sharedPreferences.getString(key, null);
    Type type = new TypeToken<ArrayList<ModelWelcome>>() {
    }.getType();
 return gson.fromJson(json, type);}}

从SharedPreference中保存和检索ArrayList

 public static void addToPreference(String id,Context context) {
        SharedPreferences sharedPreferences = context.getSharedPreferences(Constants.MyPreference, Context.MODE_PRIVATE);
        ArrayList<String> list = getListFromPreference(context);
        if (!list.contains(id)) {
            list.add(id);
            SharedPreferences.Editor edit = sharedPreferences.edit();
            Set<String> set = new HashSet<>();
            set.addAll(list);
            edit.putStringSet(Constant.LIST, set);
            edit.commit();

        }
    }
    public static ArrayList<String> getListFromPreference(Context context) {
        SharedPreferences sharedPreferences = context.getSharedPreferences(Constants.MyPreference, Context.MODE_PRIVATE);
        Set<String> set = sharedPreferences.getStringSet(Constant.LIST, null);
        ArrayList<String> list = new ArrayList<>();
        if (set != null) {
            list = new ArrayList<>(set);
        }
        return list;
    }

我能找到的最好的方法是一个使一个2D数组的键,并把数组的自定义项在2-D数组的键,然后检索它通过启动的2D arra。 我不喜欢使用字符串集的想法,因为大多数android用户仍然使用Gingerbread,使用字符串集需要蜂巢。

示例代码: 这里ditor是共享的pref编辑器,rowitem是我的自定义对象。

editor.putString(genrealfeedkey[j][1], Rowitemslist.get(j).getname());
        editor.putString(genrealfeedkey[j][2], Rowitemslist.get(j).getdescription());
        editor.putString(genrealfeedkey[j][3], Rowitemslist.get(j).getlink());
        editor.putString(genrealfeedkey[j][4], Rowitemslist.get(j).getid());
        editor.putString(genrealfeedkey[j][5], Rowitemslist.get(j).getmessage());