Sharedpreference 不起作用，没有运行时错误

Question

我正在使用SharedPreferences 将联系人存储在RecyclerView 中，以便我可以处理存储的联系人。在代码中，没有运行时错误，但仍然无法检索数据以显示在RecyclerView 中。 我使用了multicontactpicker 依赖项，我还尝试为首选项创建一个单独的类，但它不起作用

public class emergencyContact extends AppCompatActivity {
    private static final int CONTACT_PICKER_REQUEST = 202;
    private Button addContactsBtn;
    private ArrayList<ContactResult> list;

    public static final String SHARE_PREFS = "sheredPrefs";


    RecyclerView recyclerView;
    ContactAdapter adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_emergency_contact);


            loadData();
            


        addContactsBtn = findViewById(R.id.add_contacts_btn);
        addContactsBtn.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                new MultiContactPicker.Builder(emergencyContact.this) //Activity/fragment context
                        .theme(R.style.MyCustomPickerTheme) //Optional - default: MultiContactPicker.Azure
                        .hideScrollbar(false) //Optional - default: false
                        .showTrack(true) //Optional - default: true
                        .searchIconColor(Color.WHITE) //Option - default: White
                        .setChoiceMode(MultiContactPicker.CHOICE_MODE_MULTIPLE) //Optional - default: CHOICE_MODE_MULTIPLE
                        .handleColor(ContextCompat.getColor(emergencyContact.this, R.color.azureColorPrimary)) //Optional - default: Azure Blue
                        .bubbleColor(ContextCompat.getColor(emergencyContact.this, R.color.azureColorPrimary)) //Optional - default: Azure Blue
                        .bubbleTextColor(Color.WHITE) //Optional - default: White
                        .setTitleText("Select Contacts") //Optional - default: Select Contacts

                        .setLoadingType(MultiContactPicker.LOAD_ASYNC) //Optional - default LOAD_ASYNC (wait till all loaded vs stream results)
                        .limitToColumn(LimitColumn.NONE) //Optional - default NONE (Include phone + email, limiting to one can improve loading time)
                        .setActivityAnimations(android.R.anim.fade_in, android.R.anim.fade_out,
                                android.R.anim.fade_in,
                                android.R.anim.fade_out) //Optional - default: No animation overrides
                        .showPickerForResult(CONTACT_PICKER_REQUEST);

            }
        });


    }
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if(requestCode == CONTACT_PICKER_REQUEST){
            if(resultCode == RESULT_OK) {

                list = MultiContactPicker.obtainResult(data);
               
                buildRecycleView();

                saveData();

            } else if(resultCode == RESULT_CANCELED){
                System.out.println("User closed the picker without selecting items.");
            }
        }
    }

    private void saveData() {
        SharedPreferences pref = getSharedPreferences(SHARE_PREFS,MODE_PRIVATE);

        SharedPreferences.Editor editor = pref.edit();
        Gson gson = new Gson();
        String jsonString = gson.toJson(list);
        editor.putString("List Key",jsonString);
        Log.e("MyTag","size="+ list.size());
        editor.apply();
    }
    private  void loadData(){
        if(list == null){
            list = new ArrayList<>();
            Log.e("loadData","Size="+list.size());

        }
        SharedPreferences pref = getSharedPreferences(SHARE_PREFS,MODE_PRIVATE);
        Gson gson = new Gson();
        String jsonString = pref.getString("List Key",null);
        Type type = new TypeToken<ArrayList<ContactResult>>(){}.getType();
        list = gson.fromJson(jsonString,type);
        Log.e("MTag","Size="+list.size());


    }
    private  void buildRecycleView(){
        recyclerView = findViewById(R.id.contact_rv);
        LinearLayoutManager LayoutManager= new LinearLayoutManager(this);
        ContactAdapter adapter = new ContactAdapter(list,this);
        recyclerView.setLayoutManager(LayoutManager);
        recyclerView.setAdapter(adapter);
        adapter.notifyDataSetChanged();

    }

我也想对选定的联系人应用功能。

Answer 1

在您的onActivityResult 中交换buildRecycleView() 和saveData() 的位置，您正在设置适配器并在将数据加载到列表之前调用notifyDataSetChanged。

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data)          
    super.onActivityResult(requestCode, resultCode, data);
    if(requestCode == CONTACT_PICKER_REQUEST){
        if(resultCode == RESULT_OK) {
            list = MultiContactPicker.obtainResult(data);           
            saveData(); //swapped, loadData first 
            buildRecycleView(); // then build recycler view
        } else if(resultCode == RESULT_CANCELED){
            System.out.println("User closed the picker without selecting items.");
        }
    }
}