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
别忘了实现Serializable:
Class dataBean implements Serializable{
public String name;
}
ArrayList<dataBean> dataBeanArrayList = new ArrayList();
https://stackoverflow.com/a/7635154/4639974
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
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。
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
这应该可以工作:
public void setSections (Context c, List<Section> sectionList){
this.sectionList = sectionList;
Type sectionListType = new TypeToken<ArrayList<Section>>(){}.getType();
String sectionListString = new Gson().toJson(sectionList,sectionListType);
SharedPreferences.Editor editor = getSharedPreferences(c).edit().putString(PREFS_KEY_SECTIONS, sectionListString);
editor.apply();
}
他们,要抓住它才:
public List<Section> getSections(Context c){
if(this.sectionList == null){
String sSections = getSharedPreferences(c).getString(PREFS_KEY_SECTIONS, null);
if(sSections == null){
return new ArrayList<>();
}
Type sectionListType = new TypeToken<ArrayList<Section>>(){}.getType();
try {
this.sectionList = new Gson().fromJson(sSections, sectionListType);
if(this.sectionList == null){
return new ArrayList<>();
}
}catch (JsonSyntaxException ex){
return new ArrayList<>();
}catch (JsonParseException exc){
return new ArrayList<>();
}
}
return this.sectionList;
}
这对我很管用。
public static void WriteSharePrefrence1(Context context, String key,
ArrayList<HashMap<String, String>> value)
{
final SharedPreferences preferences =
PreferenceManager.getDefaultSharedPreferences(context);
SharedPreferences.Editor editor = preferences.edit();
Gson gson = new Gson();
String json = gson.toJson(value);
editor.putString(key, json);
editor.commit();
}
public static ArrayList<HashMap<String, String>> ReadSharePrefrence1(Context context,
String key)
{
String data;
Gson gson = new Gson();
ArrayList<HashMap<String, String>> items = new ArrayList<>();
final SharedPreferences preferences =
PreferenceManager.getDefaultSharedPreferences(context);
final SharedPreferences.Editor editor = preferences.edit();
data = preferences.getString(key, "");
Type type = new TypeToken<ArrayList<HashMap<String, String>>>() {}.getType();
items = gson.fromJson(data, type);
return items;
}
推荐文章
- 警告:API ' variable . getjavacompile()'已过时,已被' variable . getjavacompileprovider()'取代
- 安装APK时出现错误
- 碎片中的onCreateOptionsMenu
- TextView粗体通过XML文件?
- 如何使线性布局的孩子之间的空间?
- DSL元素android.dataBinding。enabled'已过时,已被'android.buildFeatures.dataBinding'取代
- ConstraintLayout:以编程方式更改约束
- PANIC: AVD系统路径损坏。检查ANDROID_SDK_ROOT值
- 如何生成字符串类型的buildConfigField
- Recyclerview不调用onCreateViewHolder
- Android API 21工具栏填充
- Android L中不支持操作栏导航模式
- 如何分裂()一个分隔字符串到一个列表<字符串>
- 如何在TextView中添加一个子弹符号?
- PreferenceManager getDefaultSharedPreferences在Android Q中已弃用