I have a list of item in navigationview witch are added programmatically - and I save and restore them using sharedpreferences, everything works fine.But the problem is that I can't delete an item from sharedpreferences.I retrieve the item index using the title of the current item clicked - the code works fine - the item position is retrieved correctly but is not deleted from shared preferences, nothing works.What can I do to solve this problem?
This is my code:
private void saveData() {
SharedPreferences sharedPreferences = getSharedPreferences(SHARED_PREF_LIST_KEY, MODE_PRIVATE);
SharedPreferences.Editor editor = sharedPreferences.edit();
Gson gson = new Gson();
String json = gson.toJson(navItems);
editor.putString(SHARED_PREF_LIST_KEY_ITEM, json);
editor.apply();
}
private void loadData() {
SharedPreferences sharedPreferences = getSharedPreferences(SHARED_PREF_LIST_KEY, MODE_PRIVATE);
Gson gson = new Gson();
String json = sharedPreferences.getString(SHARED_PREF_LIST_KEY_ITEM, null);
Type type = new TypeToken<ArrayList<NavItem>>() {
}.getType();
navItems = gson.fromJson(json, type);
if (navItems == null) {
navItems = new ArrayList<>();
}
}
private void deleteData(NavItem navItem) {
SharedPreferences sharedPreferences = getSharedPreferences(SHARED_PREF_LIST_KEY, MODE_PRIVATE);
Gson gson = new Gson();
String json = sharedPreferences.getString(SHARED_PREF_LIST_KEY_ITEM, null);
Type type = new TypeToken<ArrayList<NavItem>>() {
}.getType();
navItems = gson.fromJson(json, type);
if (navItems != null) {
navItems.remove(navItem);
Toast.makeText(this, "List " + navItem.getName() + "
deleted ", Toast.LENGTH_SHORT).show();
saveData(); // save updated data to shared preferences
}
}
int position = navViewArray.findItemString(checkItemTitle);
Toast.makeText(this, "position " + position,
Toast.LENGTH_SHORT).show();
NavItem navItem = navItems.get(position);
deleteData(navItem);
public class NavItem {
private String name;
public NavItem(String name) {
this.name = name;
}
public String getName() {
return name;
}
}
public class NavViewArray {
private List<NavItem> navItems;
public NavViewArray(List<NavItem> items) {
this.navItems = new ArrayList<>(items);
}
public int findItemString(String itemName) {
for (int i = 0; i < navItems.size(); i++) {
NavItem navItem = navItems.get(i);
if (itemName.equals(navItem.getName())) {
return i;
}
}
return -1;
}
}
To be able to find the item in the List
using the item itself, you need to implement equals and hashcode.
For this line of code to work navItems.remove(navItem);
You need the NavItem class to override equals
and hashcode
i.e. here:
public class NavItem {
private String name;
public NavItem(String name) {
this.name = name;
}
public String getName() {
return name;
}
// ADD THE BELOW
@Override
public boolean equals(NavItem other) {
return name.equals(other.name);
}
@Override
public int hashcode() {
return name.hashcode();
}
}
This is a very simple equals and hashcode, you can use the IDE to generate your equals and hashcode which will do a better job of taking all fields into account.
https://www.jetbrains.com/help/idea/generate-equals-and-hashcode-wizard.html
You can also validate that the item has been removed, as the removed item is returned:
NavItem removed= navItems.remove(navItem);
Toast.makeText(this, "List " + removed.getName() + "deleted ",b Toast.LENGTH_SHORT).show();