使用共享偏好检索数据

Question

我可以在另一个类中检索单个字符串数据的共享首选项，该类有一个叫 "S "的类，该类有一个叫 "S "的类，该类有一个叫 "S "的类，该类有一个叫 "S "的类，该类有一个叫 "S "的类，该类有一个叫 "S "的类，该类有一个叫 "S "的类，该类有一个叫 "S "的类，该类有一个叫 "S "的类，该类有一个叫 "S "的类，该类有一个叫 "S "的类，该类有一个叫 "S "的类，该类有一个叫 "S "的类，该类有一个叫 "S "的类，该类有一个叫 "S "的类，该类有一个叫 "S "的类，该类有一个叫 "S "的类。 recyclerView的 阵列列表

我有一个保存按钮的活动，这将保存的日期和时间，日期和时间指定的应用程序本身，我想检索相同的数据在另一个活动，这有一个。recyclerView的 阵列列表 .

保存按钮只能保存数据，还有一个按钮，通过它我将进入另一个活动。

public class StudentListActivity extends AppCompatActivity {

private RecyclerView recyclerView;
private RecyclerView.Adapter rAdapter;
private RecyclerView.LayoutManager layoutManager;
ArrayList<ListOfNames> listOfNames;


SharedPreferences sharedPreferences;
SharedPreferences.Editor editor;

String t1 = "10";
String t2 = "100%";
Bundle bundle;
String subName;
Toolbar toolbar;


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

    toolbar = findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);

    bundle = getIntent().getExtras();
    subName = bundle.getString("Subject Name");
    if (bundle != null) {
        getSupportActionBar().setTitle(subName);
    }
    loadData();


    Calendar calendar = Calendar.getInstance();
    String currentDate = DateFormat.getDateTimeInstance().format(calendar.getTime());


    toolbar.setSubtitle(currentDate);
    fabButton();
    buildRecyclerView();
}

@Override
public void onBackPressed() {
    super.onBackPressed();
    Intent intent = new Intent(this, ScrollingActivity.class);
    intent.putExtra("count", listOfNames.size());
    startActivity(intent);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.main_menu, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(@NonNull MenuItem item) {
    switch (item.getItemId()) {
        case R.id.item1:
            handleDate();

            return true;
        case R.id.item2:
            Intent intent = new Intent(this, PastAttendences.class);

            startActivity(intent);

            return true;

        case R.id.title3:

/ 我想在这里使用sharedPrerefnces来保存日期时间。

            return true;
    }

    return super.onOptionsItemSelected(item);
}

public void handelTime(final CharSequence charSequence) {

    final Calendar calendar = Calendar.getInstance();

    int Hour = calendar.get(Calendar.HOUR);
    int Minute = calendar.get(Calendar.MINUTE);

    boolean is24Hour = android.text.format.DateFormat.is24HourFormat(this);

    TimePickerDialog timePickerDialog = new TimePickerDialog(this, new TimePickerDialog.OnTimeSetListener() {
        @Override
        public void onTimeSet(TimePicker view, int Hour, int Minute) {


            Calendar calendar1 = Calendar.getInstance();

            calendar1.set(Calendar.HOUR, Hour);
            calendar1.set(Calendar.MINUTE, Minute);

            CharSequence charSequence1 = android.text.format.DateFormat.format("HH.mm", calendar1);
            toolbar.setSubtitle(charSequence + " " + charSequence1);
        }
    }, Hour, Minute, is24Hour);
    timePickerDialog.show();
}

public void handleDate() {

    final Calendar calendar = Calendar.getInstance();

    int year = calendar.get(Calendar.YEAR);
    int month = calendar.get(Calendar.MONTH);
    int date = calendar.get(Calendar.DATE);

    DatePickerDialog datePickerDialog = new DatePickerDialog(this, new DatePickerDialog.OnDateSetListener() {
        @Override
        public void onDateSet(DatePicker view, int year, int month, int date) {


            Calendar calendar1 = Calendar.getInstance();

            calendar1.set(Calendar.YEAR, year);
            calendar1.set(Calendar.MONTH, month);
            calendar1.set(Calendar.DATE, date);

            CharSequence charSequence = android.text.format.DateFormat.format("dd-MMM-yyyy", calendar1);

            handelTime(charSequence);
        }
    }, year, month, date);

    datePickerDialog.show();
}


private void buildRecyclerView() {

    recyclerView = findViewById(R.id.recyclerView2);
    recyclerView.hasFixedSize();
    layoutManager = new LinearLayoutManager(StudentListActivity.this);
    rAdapter = new AdapterForStudentList(listOfNames);

    recyclerView.setLayoutManager(layoutManager);
    recyclerView.setAdapter(rAdapter);

    ItemTouchHelper itemTouchHelper = new ItemTouchHelper(simpleCallback);
    itemTouchHelper.attachToRecyclerView(recyclerView);

}

public void insertData(String text, String t1, String t2) {
    ListOfNames lt = new ListOfNames(text, t1, t2);
    listOfNames.add(lt);
    rAdapter.notifyDataSetChanged();

}

public void saveData() {
    sharedPreferences = getSharedPreferences("SHARED PREF", MODE_PRIVATE);
    editor = sharedPreferences.edit();

    Gson gson = new Gson();
    String json = gson.toJson(listOfNames);
    editor.putString(subName, json);
    editor.apply();
}

public void loadData() {


    sharedPreferences = getSharedPreferences("SHARED PREF", MODE_PRIVATE);

    Gson gson = new Gson();
    String json = sharedPreferences.getString(subName, null);
    Type type = new TypeToken<ArrayList<ListOfNames>>() {
    }.getType();

    listOfNames = gson.fromJson(json, type);

    if (listOfNames == null) {
        listOfNames = new ArrayList<>();
    }
}

ListOfNames deletedItem = null;
ItemTouchHelper.SimpleCallback simpleCallback = new ItemTouchHelper.SimpleCallback(0, ItemTouchHelper.LEFT) {
    @Override
    public boolean onMove(@NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder, @NonNull RecyclerView.ViewHolder target) {
        return false;
    }

    @Override
    public void onSwiped(@NonNull RecyclerView.ViewHolder viewHolder, int direction) {
        final int position = viewHolder.getAdapterPosition();
        String name = listOfNames.get(position).getStudentName();

        deletedItem = listOfNames.get(position);
        listOfNames.remove(deletedItem);

        sharedPreferences = getSharedPreferences("SHARED PREF", MODE_PRIVATE);
        editor = sharedPreferences.edit();
        editor.remove("text");


        saveData();
        editor.apply();
        rAdapter.notifyItemRemoved(position);

        Snackbar.make(recyclerView, name + "Deleted", Snackbar.LENGTH_LONG)
                .setAction("Undo", new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        listOfNames.add(position, deletedItem);
                        rAdapter.notifyItemInserted(position);

                        saveData();
                    }
                }).show();
    }

    @Override
    public void onChildDrawOver(@NonNull Canvas c, @NonNull RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, boolean isCurrentlyActive) {
        new RecyclerViewSwipeDecorator.Builder(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive)

                .addSwipeLeftBackgroundColor(ContextCompat.getColor(StudentListActivity.this, R.color.my_background))
                .addSwipeLeftActionIcon(R.drawable.ic_delete_black_24dp)
                .create()
                .decorate();
        super.onChildDrawOver(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive);

    }
};

public void fabButton() {
    FloatingActionButton floatingActionButton = findViewById(R.id.fab2);
    floatingActionButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            AlertDialog.Builder b = new AlertDialog.Builder(StudentListActivity.this);
            View view = getLayoutInflater().inflate(R.layout.dialogbox_frontpage, null);

            final EditText editText = view.findViewById(R.id.editText);
            b.setView(view);
            b.setTitle("Student name");
            b.setPositiveButton("ok", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    String text = editText.getText().toString();

                    if (text.isEmpty()) {
                        Toast.makeText(StudentListActivity.this, "Please add subject name", Toast.LENGTH_SHORT).show();
                    } else {
                        insertData(text, t1, t2);
                        saveData();
                    }
                }
            });
            b.setNegativeButton("cancel", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    dialog.dismiss();
                }
            });
            b.setCancelable(false);
            b.show();
        }
    });
}

}

下一个活动

public class PastAttendences extends AppCompatActivity {
RecyclerView recyclerView;
RecyclerView.Adapter adapter;
RecyclerView.LayoutManager layoutManager;

ArrayList<ListOfPastAttendences> mItems;
public static final String DATETIME = "dateTime";

@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setContentView(R.layout.past_attendence);
    Toolbar toolbar = findViewById(R.id.attendenceToolbar);
    setSupportActionBar(toolbar);
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);
    getSupportActionBar().setTitle("Past Attendances");


    mItems = new ArrayList<>();
    buildRecyclerView();

}


public void buildRecyclerView() {
    recyclerView = findViewById(R.id.pARecyclerView);
    recyclerView.hasFixedSize();
    layoutManager = new LinearLayoutManager(this);
    adapter = new PastAttendenceAdapter(mItems);

    recyclerView.setLayoutManager(layoutManager);
    recyclerView.setAdapter(adapter);
}

}

Answer 1

U可以Intiate sharedPref(如图所示) https:/www.tutorialspoint.comandroidandroid_shared_preferences.htm) :-

SharedPreferences sharedpreferences = getSharedPreferences(MyPREFERENCES, Context.MODE_PRIVATE);
Editor editor = sharedpreferences.edit();
editor.putString("key", "value");
editor.commit();

U可以通过使用(如图所示)得到sharedpref。https:/stackoverflow.coma4800111212987677):-。

      SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(context);
      preferences.getString(key, null);