java - 回收器 View 未使用 notificationDataSetChanged() 进行更新；

Question

当我关闭该对话框时，它不会使用新数据刷新其下方的 Activity 。我需要手动刷新 Activity 或启动一个新 Activity (看起来很奇怪)才能显示它，我不确定为什么我的 recyclerViewAdapter.notifyDataSetChanged();在 saveItem 方法中不起作用。

package com.bawp.babyneeds;

import android.app.AlertDialog;
import android.content.Intent;
import android.os.Bundle;
import android.os.Handler;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;

import com.bawp.babyneeds.data.DatabaseHandlerDiary;
import com.bawp.babyneeds.model.Diary;
import com.bawp.babyneeds.ui.RecyclerViewAdapter;

import java.util.ArrayList;
import java.util.List;

public class ListActivity extends AppCompatActivity {
    private static final String TAG = "ListActivity";
    private RecyclerView recyclerView;
    private RecyclerViewAdapter recyclerViewAdapter;
    private List<Diary> diaryList;
    private DatabaseHandlerDiary databaseHandlerDiary;
    private FloatingActionButton fab;
    private AlertDialog.Builder builder;
    private AlertDialog alertDialog;
    private Button saveButton;
    private EditText diaryName;
    private EditText diaryDesc;


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

        recyclerView = findViewById(R.id.recyclerview);
        fab = findViewById(R.id.fab);


        databaseHandlerDiary = new DatabaseHandlerDiary(this);
        recyclerView.setHasFixedSize(true);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));

        diaryList = new ArrayList<>();

        //Get items from db
        diaryList = databaseHandlerDiary.getAllDiaries();

        for (Diary diary : diaryList) {

            Log.d(TAG, "onCreate: " + diary.getDiaryDesc());

        }

        recyclerViewAdapter = new RecyclerViewAdapter(this, diaryList);
        recyclerView.setAdapter(recyclerViewAdapter);
        recyclerViewAdapter.notifyDataSetChanged();

        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                createPopDialog();
            }
        });
    }


    private void createPopDialog() {
        builder = new AlertDialog.Builder(this);
        View view = getLayoutInflater().inflate(R.layout.popup, null);
        diaryName = view.findViewById(R.id.edit_text_name_diary);
        diaryDesc = view.findViewById(R.id.edit_text_desc_diary);
        saveButton = view.findViewById(R.id.saveButton);

        builder.setView(view);
        alertDialog = builder.create();
        alertDialog.show();

        saveButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (!diaryName.getText().toString().isEmpty()
                        && !diaryDesc.getText().toString().isEmpty()) {
                    saveItem(v);
                    //recyclerViewAdapter.notifyDataSetChanged();
                }else {
                    Snackbar.make(v, "Empty Fields not Allowed", Snackbar.LENGTH_SHORT)
                            .show();
                }
            }
        });
    }


    private void saveItem(View view) {
        //Todo: save each baby diary to db
        final Diary diary = new Diary();

        String newDiary = diaryName.getText().toString().trim();
        String newDesc = diaryDesc.getText().toString().trim();

        diary.setDiaryName(newDiary);
        diary.setDiaryDesc(newDesc);

        databaseHandlerDiary.addDiary(diary);
        recyclerViewAdapter.notifyDataSetChanged(); // <-------------------------this is not working

        Snackbar.make(view, "Diary Saved",Snackbar.LENGTH_SHORT)
                .show();


        new Handler().postDelayed(new Runnable() {
            @Override
            public void run() {
                alertDialog.dismiss();

                //Todo: move to next screen - details screen
                //startActivity(new Intent(ListActivity.this, ListActivity.class));
                //finish();

            }
        }, 1000);
    }
}

谢谢...

添加了DatabaseHandlerDiary类

package com.bawp.babyneeds.data;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import com.bawp.babyneeds.model.Diary;
import com.bawp.babyneeds.R;
import com.bawp.babyneeds.util.Util;

import java.text.DateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;

public class DatabaseHandlerDiary extends SQLiteOpenHelper {

    public DatabaseHandlerDiary(Context context) {
        super(context, Util.DATABASE_NAME_DIARY, null, Util.DATA_BASE_VERSION_DIARY);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        String CREATE_DIARY_TABLE = "CREATE TABLE " + Util.TABLE_NAME_DIARY + " ("
                + Util.KEY_ID_DIARY + " INTEGER PRIMARY KEY," + Util.KEY_NAME_DIARY + " TEXT,"
                + Util.KEY_DESC_DIARY + " TEXT," + Util.KEY_DATE_ADDED_DIARY + ")";
        db.execSQL(CREATE_DIARY_TABLE);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        String DROP_TABLE = String.valueOf(R.string.db_drop);
        db.execSQL(DROP_TABLE, new String[]{Util.DATABASE_NAME_DIARY});

        //create new table
        onCreate(db);
    }

    //CRUD: create read update delete

    //add diary
    public void addDiary(Diary diary) {
        SQLiteDatabase db = this.getWritableDatabase();

        ContentValues values = new ContentValues();
        values.put(Util.KEY_NAME_DIARY, diary.getDiaryName());
        values.put(Util.KEY_DESC_DIARY, diary.getDiaryDesc());
        values.put(Util.KEY_DATE_ADDED_DIARY, diary.getDateDiaryAdded());

        //^ insert to row
        db.insert(Util.TABLE_NAME_DIARY, null, values);
        db.close();
    }

    //get diary
    public Diary getDiary(int id) {
        SQLiteDatabase db = this.getReadableDatabase();

        Cursor cursor = db.query(Util.TABLE_NAME_DIARY, new String[]{
                        Util.KEY_NAME_DIARY, Util.KEY_DESC_DIARY, Util.KEY_DATE_ADDED_DIARY},
                Util.KEY_ID_DIARY +"=?", new String[]{String.valueOf(id)},
                null, null, null);

        if (cursor != null) {
            cursor.moveToFirst();
        }

        Diary diary = new Diary();
        diary.setDiaryId(Integer.parseInt(cursor.getString(0)));
        diary.setDiaryName(cursor.getString(1));
        diary.setDiaryDesc(cursor.getString(2));

        return diary;
    }

    //get all diaries
    public List<Diary> getAllDiaries() {
        SQLiteDatabase db = this.getReadableDatabase();

        List<Diary> diaryList = new ArrayList<>();

        Cursor cursor = db.query(Util.TABLE_NAME_DIARY,
                new String[]{Util.KEY_ID_DIARY,
                        Util.KEY_NAME_DIARY,
                        Util.KEY_DESC_DIARY,
                        Util.KEY_DATE_ADDED_DIARY},
                null, null, null, null,
                Util.KEY_DATE_ADDED_DIARY + " DESC");

        if (cursor.moveToFirst()) {
            do {
                Diary diary = new Diary();
                diary.setDiaryId(Integer.parseInt(cursor.getString(cursor.getColumnIndex(Util.KEY_ID_DIARY))));
                diary.setDiaryName(cursor.getString(cursor.getColumnIndex(Util.KEY_NAME_DIARY)));
                diary.setDiaryDesc(cursor.getString(cursor.getColumnIndex(Util.KEY_DESC_DIARY)));

                //convert Timestamp to something readable
                DateFormat dateFormat = DateFormat.getDateInstance();
                String formattedDate = dateFormat.format(new Date(cursor.getLong(cursor.getColumnIndex(Util.KEY_DATE_ADDED_DIARY)))
                        .getTime()); // Feb 23, 2020
                diary.setDateDiaryAdded(formattedDate);

                //Add to arraylist
                diaryList.add(diary);
            } while (cursor.moveToNext());
        }
        return diaryList;
    }

    public int updateItem(Diary diary) {
        SQLiteDatabase db = this.getWritableDatabase();

        ContentValues values = new ContentValues();
        values.put(Util.KEY_NAME_DIARY, diary.getDiaryName());
        values.put(Util.KEY_DESC_DIARY, diary.getDiaryDesc());
        values.put(Util.KEY_DATE_ADDED_DIARY, java.lang.System.currentTimeMillis());//timestamp of the system

        //update row
        return db.update(Util.TABLE_NAME_DIARY, values,
                Util.KEY_ID_DIARY + "=?",
                new String[]{String.valueOf(diary.getDiaryId())});

    }

    //Todo: Add Delete Item
    public void deleteItem(int id) {
        SQLiteDatabase db = this.getWritableDatabase();
        db.delete(Util.TABLE_NAME_DIARY,
                Util.KEY_ID_DIARY + "=?",
                new String[]{String.valueOf(id)});

        //close
        db.close();

    }

    //Todo: getItemCount
    public int getItemsCount() {
        String countQuery = "SELECT * FROM " + Util.TABLE_NAME_DIARY;
        SQLiteDatabase db = this.getReadableDatabase();

        Cursor cursor = db.rawQuery(countQuery, null);

        return cursor.getCount();

    }

}

Answer 1

将diary添加到diaryList，然后通知您的适配器

diaryList.add(diary);

recyclerViewAdapter.notifyDataSetChanged();

为了使其更加优化，请调用

recyclerViewAdapter.notifyItemInserted(diaryList.size() - 1)

您不需要更新所有数据集，您只需要通知添加的项目