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
我的utils类保存列表到SharedPreferences
public class SharedPrefApi {
private SharedPreferences sharedPreferences;
private Gson gson;
public SharedPrefApi(Context context, Gson gson) {
this.sharedPreferences = context.getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE);
this.gson = gson;
}
...
public <T> void putList(String key, List<T> list) {
SharedPreferences.Editor editor = sharedPreferences.edit();
editor.putString(key, gson.toJson(list));
editor.apply();
}
public <T> List<T> getList(String key, Class<T> clazz) {
Type typeOfT = TypeToken.getParameterized(List.class, clazz).getType();
return gson.fromJson(getString(key, null), typeOfT);
}
}
使用
// for save
sharedPrefApi.putList(SharedPrefApi.Key.USER_LIST, userList);
// for retrieve
List<User> userList = sharedPrefApi.getList(SharedPrefApi.Key.USER_LIST, User.class);
. 我的utils的完整代码//检查使用实例的活动代码
正如@nirav所说,最好的解决方案是使用Gson实用工具类将其作为json文本存储在sharedpreferences中。下面是示例代码:
//Retrieve the values
Gson gson = new Gson();
String jsonText = Prefs.getString("key", null);
String[] text = gson.fromJson(jsonText, String[].class); //EDIT: gso to gson
//Set the values
Gson gson = new Gson();
List<String> textList = new ArrayList<String>(data);
String jsonText = gson.toJson(textList);
prefsEditor.putString("key", jsonText);
prefsEditor.apply();
您可以将其转换为JSON字符串,并将字符串存储在SharedPreferences中。
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);}}
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…
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