Words 词汇记录

1. 配置应用

  说明: Jetpack 组件实现 (Room，ViewModel，LiveData，Repository，AsyncTack)

  1.1 build.gradle 文件引用库

dependencies {
    def room_version = "2.4.3"
    implementation "androidx.room:room-runtime:$room_version"
    annotationProcessor "androidx.room:room-compiler:$room_version"
    implementation 'androidx.navigation:navigation-fragment:2.5.1'
    implementation 'androidx.navigation:navigation-ui:2.5.1'
}

  1.2 ids.xml 文件下添加 id

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <item name="word_for_view_holder" type="id" />
</resources>

  1.3 添加矢量图标文件, 如: ic_baseline_search_24.xml

<vector xmlns:android="http://schemas.android.com/apk/res/android"
    android:width="24dp"
    android:height="24dp"
    android:tint="#FFFFFF"
    android:viewportWidth="24"
    android:viewportHeight="24">
    <path
        android:fillColor="@android:color/white"
        android:pathData="M15.5,14h-0.79l-0.28,-0.27C15.41,12.59 16,11.11 16,9.5 16,5.91 13.09,3 9.5,3S3,5.91 3,9.5 5.91,16 9.5,16c1.61,0 3.09,-0.59 4.23,-1.57l0.27,0.28v0.79l5,4.99L20.49,19l-4.99,-5zM9.5,14C7.01,14 5,11.99 5,9.5S7.01,5 9.5,5 14,7.01 14,9.5 11.99,14 9.5,14z" />
</vector>

  1.4 添加其他矢量图标，依次从 Android Studio 系统自动图标中导入

      1. ic_baseline_add_24.xml
      2. ic_baseline_chevron_right_24.xml
      3. ic_baseline_delete_forever_24.xml

  1.5 menu 文件夹添加菜单布局文件: main_menu.xml

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">
    <item
        android:id="@+id/clear_data"
        android:title="清空数据" />
    <item
        android:id="@+id/switch_type"
        android:title="切换视图" />
    <item
        android:id="@+id/app_bar_search"
        android:icon="@android:drawable/ic_menu_search"
        android:title="Search"
        app:actionViewClass="android.widget.SearchView"
        app:showAsAction="always" />
</menu>

  1.6 navigation 文件夹添加 Fragment 导航文件: navigation.xml

<?xml version="1.0" encoding="utf-8"?>
<navigation xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/navigation"
    app:startDestination="@id/wordsFragment">

    <fragment
        android:id="@+id/wordsFragment"
        android:name="com.example.words.WordsFragment"
        android:label="Words"
        tools:layout="@layout/fragment_words">
        <action
            android:id="@+id/action_wordsFragment_to_addFragment"
            app:destination="@id/addFragment"
            app:enterAnim="@anim/nav_default_enter_anim" />
    </fragment>
    <fragment
        android:id="@+id/addFragment"
        android:name="com.example.words.AddFragment"
        android:label="Add"
        tools:layout="@layout/fragment_add" />
</navigation>

2. 搭建数据库

  2.1 创建实体类, Word.java

@Entity
public class Word {
    @PrimaryKey(autoGenerate = true)
    private int id; //主键
    @ColumnInfo(name = "english_word")
    private String word;
    @ColumnInfo(name = "chinese_meaning")
    private String chineseMeaning;
    @ColumnInfo(name = "chinese_invisible")
    private boolean chineseInvisible;
//    @ColumnInfo(name = "foo_data")
//    private boolean foo;
//    @ColumnInfo(name = "bar_data")
//    private boolean bar;
    public Word(String word, String chineseMeaning) {
        this.word = word;
        this.chineseMeaning = chineseMeaning;
    }
    public boolean isChineseInvisible() {
        return chineseInvisible;
    }
    public void setChineseInvisible(boolean chineseInvisible) {
        this.chineseInvisible = chineseInvisible;
    }
//    public boolean isBar() {
//        return bar;
//    }
//
//    public void setBar(boolean bar) {
//        this.bar = bar;
//    }
//
//    public boolean isFoo() {
//        return foo;
//    }
//
//    public void setFoo(boolean foo) {
//        this.foo = foo;
//    }
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getWord() {
        return word;
    }
    public String getChineseMeaning() {
        return chineseMeaning;
    }
}

  2.2 操作数据库接口类, WordDao.java

@Dao //Database access object
public interface WordDao {
    @Insert
    void insertWords(Word... words);

    @Update
    void updateWords(Word... words);

    @Delete
    void deleteWords(Word... words);

    @Query("DELETE FROM WORD")
    void deleteAllWords();

    @Query("SELECT * FROM WORD ORDER BY ID DESC")
    //List<Word> getAllWords();
    LiveData<List<Word>> getAllWordsLive();

    @Query("SELECT * FROM WORD WHERE english_word LIKE :pattern ORDER BY ID DESC ")
    LiveData<List<Word>>findWordsWithPattern(String pattern);
}

  2.3 创建维护数据库与表类, WordDatabase.java

//singleton 只允许生成一个实例
@Database(entities = {Word.class}, version = 5, exportSchema = false)
public abstract class WordDatabase extends RoomDatabase {
    private static WordDatabase INSTANCE;

    //synchronized: 解决多个线程下调用，创建多个实例问题
    static synchronized WordDatabase getDatabase(Context context) {
        if (INSTANCE == null) {
            //fallbackToDestructiveMigration 把当前的数据清空，创建新的库
            //addMigrations 添加迁移的策略
            INSTANCE = Room.databaseBuilder(context.getApplicationContext(), WordDatabase.class, "word_database")
                    .addMigrations(migration_4_5)
                    .build();
        }
        return INSTANCE;
    }

    public abstract WordDao getWordDao();

    //添加字段操作
    static final Migration migration_2_3 = new Migration(2, 3) {
        @Override
        public void migrate(@NonNull SupportSQLiteDatabase database) {
            database.execSQL("ALTER TABLE word ADD COLUMN bar_data INTEGER NOT NULL DEFAULT 1");
        }
    };

    //删除字段操作
    static final Migration migration_3_4 = new Migration(3, 4) {
        @Override
        public void migrate(@NonNull SupportSQLiteDatabase database) {
            database.execSQL("CREATE TABLE word_temp (id INTEGER PRIMARY KEY NOT NULL , english_word TEXT," +
                    "chinese_meaning TEXT)");
            database.execSQL("INSERT INTO word_temp (id,english_word,chinese_meaning) " +
                    "SELECT id,english_word,chinese_meaning FROM word");
            database.execSQL("DROP TABLE word");
            database.execSQL("ALTER TABLE word_temp RENAME to word");
        }
    };

    //添加字段操作
    private static final Migration migration_4_5 = new Migration(4, 5) {
        @Override
        public void migrate(@NonNull SupportSQLiteDatabase database) {
            database.execSQL("ALTER TABLE word ADD COLUMN chinese_invisible INTEGER NOT NULL DEFAULT 0");
        }
    };
}

  2.4 创建数据库, 操作数据库类, WordRepository.java

//Repository 仓库 获取数据的意思
class WordRepository {
    private WordDao wordDao;
    private LiveData<List<Word>> allWordsLive;

    WordRepository(Context context) {
        WordDatabase wordDatabase = WordDatabase.getDatabase(context);
        wordDao = wordDatabase.getWordDao();
        allWordsLive = wordDao.getAllWordsLive();
    }

    void insertWords(Word... words) {
        new InsertAsyncTask(wordDao).execute(words);
    }

    void updateWords(Word... words) {
        new UpdateAsyncTask(wordDao).execute(words);
    }

    void deleteWords(Word... words) {
        new DeleteAsyncTask(wordDao).execute(words);
    }

    void deleteAllWords() {
        new DeleteAllAsyncTask(wordDao).execute();
    }

    LiveData<List<Word>> getAllWordsLive() {
        return allWordsLive;
    }

    LiveData<List<Word>> findWordsWithPattern(String pattern) {
        return wordDao.findWordsWithPattern("%" + pattern + "%");
    }

    static class InsertAsyncTask extends AsyncTask<Word, Void, Void> {
        private WordDao wordDao;

        InsertAsyncTask(WordDao wordDao) {
            this.wordDao = wordDao;
        }

        @Override
        protected Void doInBackground(Word... words) {
            wordDao.insertWords(words);
            return null;
        }
    }

    static class UpdateAsyncTask extends AsyncTask<Word, Void, Void> {
        private WordDao wordDao;

        UpdateAsyncTask(WordDao wordDao) {
            this.wordDao = wordDao;
        }

        @Override
        protected Void doInBackground(Word... words) {
            wordDao.updateWords(words);
            return null;
        }
    }

    static class DeleteAsyncTask extends AsyncTask<Word, Void, Void> {
        private WordDao wordDao;

        DeleteAsyncTask(WordDao wordDao) {
            this.wordDao = wordDao;
        }

        @Override
        protected Void doInBackground(Word... words) {
            wordDao.deleteWords(words);
            return null;
        }
    }

    static class DeleteAllAsyncTask extends AsyncTask<Void, Void, Void> {
        private WordDao wordDao;

        DeleteAllAsyncTask(WordDao wordDao) {
            this.wordDao = wordDao;
        }

        @Override
        protected Void doInBackground(Void... voids) {
            this.wordDao.deleteAllWords();
            return null;
        }
    }
}

3. 创建 ViewModel 类, 处理数据操作, WordViewModel.java

public class WordViewModel extends AndroidViewModel {
    private WordRepository wordRepository = null;

    public WordViewModel(@NonNull Application application) {
        super(application);
        wordRepository = new WordRepository(application);
    }

    public LiveData<List<Word>> getAllWordsLive() {
        return wordRepository.getAllWordsLive();
    }

    public LiveData<List<Word>> findWordsWithPattern(String pattern) {
        return wordRepository.findWordsWithPattern(pattern);
    }

    void insertWords(Word... words) {
        wordRepository.insertWords(words);
    }

    void updateWords(Word... words) {
        wordRepository.updateWords(words);
    }

    void deleteWords(Word... words) {
        wordRepository.deleteWords(words);
    }

    void deleteAllWords() {
        wordRepository.deleteAllWords();
    }
}

4. 词汇列表页

  4.1 创建列表内容管理器布局1: cell_card_2.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="70dp">

    <androidx.cardview.widget.CardView
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="8dp"
        android:foreground="?attr/selectableItemBackground"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent">

        <androidx.constraintlayout.widget.ConstraintLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent">

            <View
                android:id="@+id/divider2"
                android:layout_width="1dp"
                android:layout_height="0dp"
                android:layout_marginTop="8dp"
                android:background="?android:attr/listDivider"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintEnd_toStartOf="@+id/guideline9"
                app:layout_constraintStart_toEndOf="@+id/guideline9"
                app:layout_constraintTop_toTopOf="parent" />

            <androidx.constraintlayout.widget.ConstraintLayout
                android:id="@+id/constraintLayout"
                android:layout_width="0dp"
                android:layout_height="match_parent"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintEnd_toStartOf="@+id/guideline9"
                app:layout_constraintStart_toStartOf="parent"
                app:layout_constraintTop_toTopOf="parent">

                <androidx.constraintlayout.widget.Guideline
                    android:id="@+id/guideline11"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:orientation="vertical"
                    app:layout_constraintGuide_percent="0.15" />

                <TextView
                    android:id="@+id/tv_number"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:text="TextView"
                    android:textSize="16sp"
                    app:layout_constraintBottom_toBottomOf="parent"
                    app:layout_constraintEnd_toStartOf="@+id/guideline11"
                    app:layout_constraintStart_toStartOf="parent"
                    app:layout_constraintTop_toTopOf="parent"
                    tools:text="1" />

                <TextView
                    android:id="@+id/tv_english"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_marginStart="16dp"
                    android:text="TextView"
                    android:textSize="24sp"
                    app:layout_constraintBottom_toTopOf="@+id/tv_chinese"
                    app:layout_constraintEnd_toEndOf="parent"
                    app:layout_constraintHorizontal_bias="0.0"
                    app:layout_constraintStart_toStartOf="@+id/guideline11"
                    app:layout_constraintTop_toTopOf="parent" />

                <TextView
                    android:id="@+id/tv_chinese"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:text="TextView"
                    android:textSize="18sp"
                    app:layout_constraintBottom_toBottomOf="parent"
                    app:layout_constraintStart_toStartOf="@+id/tv_english"
                    app:layout_constraintTop_toBottomOf="@+id/tv_english" />

            </androidx.constraintlayout.widget.ConstraintLayout>

            <androidx.constraintlayout.widget.ConstraintLayout
                android:id="@+id/constraintLayout2"
                android:layout_width="0dp"
                android:layout_height="match_parent"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintEnd_toEndOf="parent"
                app:layout_constraintStart_toStartOf="@+id/guideline9"
                app:layout_constraintTop_toTopOf="parent">

                <Switch
                    android:id="@+id/switchChineseInvisible"
                    android:layout_width="wrap_content"
                    android:layout_height="0dp"
                    android:paddingStart="30dp"
                    android:paddingEnd="15dp"
                    app:layout_constraintBottom_toBottomOf="parent"
                    app:layout_constraintEnd_toEndOf="parent"
                    app:layout_constraintStart_toStartOf="parent"
                    app:layout_constraintTop_toTopOf="parent" />
            </androidx.constraintlayout.widget.ConstraintLayout>

            <androidx.constraintlayout.widget.Guideline
                android:id="@+id/guideline9"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:orientation="vertical"
                app:layout_constraintGuide_percent="0.8" />

        </androidx.constraintlayout.widget.ConstraintLayout>
    </androidx.cardview.widget.CardView>
</androidx.constraintlayout.widget.ConstraintLayout>

  4.2 创建列表内容管理器布局2: cell_normal_2.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="60dp"
    android:background="#FFFFFF"
    android:foreground="?attr/selectableItemBackground">

    <View
        android:id="@+id/divider"
        android:layout_width="1dp"
        android:layout_height="0dp"
        android:layout_marginTop="8dp"
        android:layout_marginBottom="8dp"
        android:background="?android:attr/listDivider"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="@+id/constraintLayout2"
        app:layout_constraintStart_toStartOf="@+id/guideline7"
        app:layout_constraintTop_toTopOf="parent" />

    <androidx.constraintlayout.widget.ConstraintLayout
        android:id="@+id/constraintLayout2"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toStartOf="@+id/guideline7"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent">

        <androidx.constraintlayout.widget.Guideline
            android:id="@+id/guideline10"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:orientation="vertical"
            app:layout_constraintGuide_percent="0.15" />

        <TextView
            android:id="@+id/tv_number"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="TextView"
            android:textSize="16sp"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toStartOf="@+id/guideline10"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            tools:text="1" />

        <TextView
            android:id="@+id/tv_english"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginStart="16dp"
            android:text="TextView"
            android:textSize="24sp"
            app:layout_constraintBottom_toTopOf="@+id/tv_chinese"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintHorizontal_bias="0.0"
            app:layout_constraintStart_toStartOf="@+id/guideline10"
            app:layout_constraintTop_toTopOf="parent" />

        <TextView
            android:id="@+id/tv_chinese"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="TextView"
            android:textSize="18sp"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintStart_toStartOf="@+id/tv_english"
            app:layout_constraintTop_toBottomOf="@+id/tv_english" />

    </androidx.constraintlayout.widget.ConstraintLayout>

    <androidx.constraintlayout.widget.ConstraintLayout
        android:id="@+id/constraintLayout"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="@+id/guideline7"
        app:layout_constraintTop_toTopOf="parent">

        <Switch
            android:id="@+id/switchChineseInvisible"
            android:layout_width="wrap_content"
            android:layout_height="0dp"
            android:paddingStart="30dp"
            android:paddingEnd="15dp"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            tools:ignore="UseSwitchCompatOrMaterialXml" />

    </androidx.constraintlayout.widget.ConstraintLayout>

    <androidx.constraintlayout.widget.Guideline
        android:id="@+id/guideline7"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        app:layout_constraintGuide_percent="0.8" />
</androidx.constraintlayout.widget.ConstraintLayout>

  4.3 创建列表内容管理器, MyAdapter.java

//内容管理器
public class MyAdapter extends ListAdapter<Word, MyAdapter.MyViewHolder> {
    private final boolean useCardView;
    private final WordViewModel viewModel;
    public MyAdapter(boolean useCardView, WordViewModel viewModel) {
        super(new DiffUtil.ItemCallback<Word>() {
            @Override
            public boolean areItemsTheSame(@NonNull Word oldItem, @NonNull Word newItem) {
                return oldItem.getId() == newItem.getId();
            }
            @Override
            public boolean areContentsTheSame(@NonNull Word oldItem, @NonNull Word newItem) {
                return (oldItem.getWord().equals(newItem.getWord()) && oldItem.getChineseMeaning().equals(newItem.getChineseMeaning()) && oldItem.isChineseInvisible() == newItem.isChineseInvisible());
            }
        });
        this.useCardView = useCardView;
        this.viewModel = viewModel;
    }

    @NonNull
    @Override
    public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        LayoutInflater layoutInflater = LayoutInflater.from(parent.getContext());
        View itemView;
        if (useCardView) {
            itemView = layoutInflater.inflate(R.layout.cell_card_2, parent, false);
        } else {
            itemView = layoutInflater.inflate(R.layout.cell_normal_2, parent, false);
        }
        MyViewHolder holder = new MyViewHolder(itemView);
        holder.itemView.setOnClickListener(view -> {
            Uri uri = Uri.parse("https://m.youdao.com/m/result?lang=en&word=" + holder.tvEnglish.getText());
            Intent intent = new Intent(Intent.ACTION_VIEW);
            intent.setData(uri);
            holder.itemView.getContext().startActivity(intent);
        });
        holder.aSwitchChineseInvisible.setOnCheckedChangeListener((compoundButton, isChecked) -> {
            Word word = (Word) holder.itemView.getTag(R.id.word_for_view_holder);
            if (isChecked) {
                holder.tvChinese.setVisibility(View.GONE);
                word.setChineseInvisible(true);
            } else {
                holder.tvChinese.setVisibility(View.VISIBLE);
                word.setChineseInvisible(false);
            }
            viewModel.updateWords(word);
        });
        return holder;
    }

    @Override
    public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {
        Word word = getItem(position);
        holder.itemView.setTag(R.id.word_for_view_holder, word);
        holder.tvNumber.setText(String.valueOf(position + 1));
        holder.tvEnglish.setText(word.getWord());
        holder.tvChinese.setText(word.getChineseMeaning());
        if (word.isChineseInvisible()) {
            holder.tvChinese.setVisibility(View.GONE);
            holder.aSwitchChineseInvisible.setChecked(true);
        } else {
            holder.tvChinese.setVisibility(View.VISIBLE);
            holder.aSwitchChineseInvisible.setChecked(false);
        }
    }

    @Override
    public void onViewAttachedToWindow(@NonNull MyViewHolder holder) {
        super.onViewAttachedToWindow(holder);
        holder.tvNumber.setText(String.valueOf(holder.getAdapterPosition() + 1));
    }

    static class MyViewHolder extends RecyclerView.ViewHolder {
        TextView tvNumber, tvEnglish, tvChinese;
        @SuppressLint("UseSwitchCompatOrMaterialCode")
        Switch aSwitchChineseInvisible;
        public MyViewHolder(@NonNull View itemView) {
            super(itemView);
            tvNumber = itemView.findViewById(R.id.tv_number);
            tvEnglish = itemView.findViewById(R.id.tv_english);
            tvChinese = itemView.findViewById(R.id.tv_chinese);
            aSwitchChineseInvisible = itemView.findViewById(R.id.switchChineseInvisible);
        }
    }
}

  4.4 创建词汇列表布局页, fragment_words.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/words_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/recycle_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

    <com.google.android.material.floatingactionbutton.FloatingActionButton
        android:id="@+id/floatingActionButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|center_horizontal"
        android:layout_marginBottom="20dp"
        android:clickable="true"
        android:focusable="true"
        android:src="@drawable/ic_baseline_add_24"
        tools:ignore="SpeakableTextPresentCheck" />
</androidx.coordinatorlayout.widget.CoordinatorLayout>

  4.5 创建实现列表页, WordsFragment.java

public class WordsFragment extends Fragment {
    private WordViewModel viewModel;
    private RecyclerView recyclerView;
    private MyAdapter myAdapter1, myAdapter2;
    private LiveData<List<Word>> filteredWords;
    private static final String VIEW_TYPE_SHP = "view_type_shp";
    private static final String IS_USING_CARD_VIEW = "is_using_card_view";
    private List<Word> allWords;
    private int temp;
    private boolean undoAction;
    private DividerItemDecoration dividerItemDecoration;//边线

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        setHasOptionsMenu(true);
        return inflater.inflate(R.layout.fragment_words, container, false);
    }

    @SuppressLint("NonConstantResourceId")
    @Override
    public boolean onOptionsItemSelected(@NonNull MenuItem item) {
        switch (item.getItemId()) {
            case R.id.clear_data:
                AlertDialog.Builder builder = new AlertDialog.Builder(requireActivity());
                builder.setTitle("清空数据");
                builder.setPositiveButton("确定", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialogInterface, int i) {
                        viewModel.deleteAllWords();
                    }
                });
                builder.setNegativeButton("取消", null);
                builder.create();
                builder.show();
                break;
            case R.id.switch_type:
                SharedPreferences shp = requireActivity().getSharedPreferences(VIEW_TYPE_SHP, Context.MODE_PRIVATE);
                boolean viewType = shp.getBoolean(IS_USING_CARD_VIEW, false);
                SharedPreferences.Editor editor = shp.edit();
                if (viewType) {
                    recyclerView.setAdapter(myAdapter1);
                    recyclerView.addItemDecoration(dividerItemDecoration);
                    editor.putBoolean(IS_USING_CARD_VIEW, false);
                } else {
                    recyclerView.setAdapter(myAdapter2);
                    recyclerView.removeItemDecoration(dividerItemDecoration);
                    editor.putBoolean(IS_USING_CARD_VIEW, true);
                }
                editor.apply();
                break;
        }
        return super.onOptionsItemSelected(item);
    }

    @Override
    public void onCreateOptionsMenu(@NonNull Menu menu, @NonNull MenuInflater inflater) {
        super.onCreateOptionsMenu(menu, inflater);
        inflater.inflate(R.menu.main_menu, menu);
        SearchView searchView = (SearchView) menu.findItem(R.id.app_bar_search).getActionView();
        searchView.setMaxWidth(720);
        searchView.setOnQueryTextListener(new SearchView.OnQueryTextListener() {
            @Override
            public boolean onQueryTextSubmit(String query) {
                return false;
            }

            @Override
            public boolean onQueryTextChange(String newText) {
                String pattern = newText.trim();
                filteredWords.removeObservers(getViewLifecycleOwner()); //...
                filteredWords = viewModel.findWordsWithPattern(pattern);
                filteredWords.observe(getViewLifecycleOwner(), words -> {
                    int temp = myAdapter1.getItemCount();
                    allWords = words;
                    if (temp != words.size()) {
                        myAdapter1.submitList(words);
                        myAdapter2.submitList(words);
                    }
                });
                return true;
            }
        });
    }

    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        viewModel = new ViewModelProvider(requireActivity()).get(WordViewModel.class);
        recyclerView = view.findViewById(R.id.recycle_view);
        recyclerView.setLayoutManager(new LinearLayoutManager((requireActivity())));
        myAdapter1 = new MyAdapter(false, viewModel);
        myAdapter2 = new MyAdapter(true, viewModel);
        recyclerView.setItemAnimator(new DefaultItemAnimator() {
            @Override
            public void onAnimationFinished(@NonNull RecyclerView.ViewHolder viewHolder) {
                super.onAnimationFinished(viewHolder);
                LinearLayoutManager linearLayoutManager = (LinearLayoutManager) recyclerView.getLayoutManager();
                if (linearLayoutManager != null) {
                    int firstPosition = linearLayoutManager.findFirstVisibleItemPosition();
                    int lastPosition = linearLayoutManager.findLastVisibleItemPosition();
                    for (int i = firstPosition; i <= lastPosition; i++) {
                        MyAdapter.MyViewHolder holder = (MyAdapter.MyViewHolder) recyclerView.findViewHolderForAdapterPosition(i);
                        if (holder != null) {
                            holder.tvNumber.setText(String.valueOf(i + 1));
                        }
                    }
                }
            }
        });
        SharedPreferences shp = requireActivity().getSharedPreferences(VIEW_TYPE_SHP, Context.MODE_PRIVATE);
        boolean viewType = shp.getBoolean(IS_USING_CARD_VIEW, false);
        dividerItemDecoration = new DividerItemDecoration(requireActivity(), DividerItemDecoration.VERTICAL);
        if (viewType) {
            recyclerView.setAdapter(myAdapter2);
        } else {
            recyclerView.setAdapter(myAdapter1);
            recyclerView.addItemDecoration(dividerItemDecoration);
        }
        filteredWords = viewModel.getAllWordsLive();
        filteredWords.observe(getViewLifecycleOwner(), words -> {
            temp = myAdapter1.getItemCount();
            allWords = words;
            if (temp != words.size()) {
                if (temp < allWords.size() && !undoAction) {
                    //recyclerView.smoothScrollToPosition(0);
                    recyclerView.smoothScrollBy(0, -200);
                }
                undoAction = false;
                //recyclerView.smoothScrollBy(0, -200);
                //提交的数据列表 会在后台进行差异化比较 根据比对结果, 来刷新界面
                myAdapter1.submitList(words);
                myAdapter2.submitList(words);
            }
        });

        new ItemTouchHelper(new ItemTouchHelper.SimpleCallback(0, ItemTouchHelper.START | ItemTouchHelper.END) {
            @Override
            public boolean onMove(@NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder, @NonNull RecyclerView.ViewHolder target) {
//                Word wordFrom = allWords.get(viewHolder.getAdapterPosition());
//                Word wordTo = allWords.get(target.getAdapterPosition());
//                int idTemp = wordFrom.getId();
//                wordFrom.setId(wordTo.getId());
//                wordTo.setId(idTemp);
//                viewModel.updateWords(wordFrom, wordTo);
//                myAdapter1.notifyItemMoved(viewHolder.getAdapterPosition(), target.getAdapterPosition());
//                myAdapter2.notifyItemMoved(viewHolder.getAdapterPosition(), target.getAdapterPosition());
                return false;
            }

            @Override
            public void onSwiped(@NonNull RecyclerView.ViewHolder viewHolder, int direction) {
                Word wordToData = allWords.get(viewHolder.getAdapterPosition());
                viewModel.deleteWords(wordToData);
                Snackbar.make(requireActivity().findViewById(R.id.words_layout), "删除了一个词汇", Snackbar.LENGTH_SHORT)
                        .setAction("撤销", view12 -> {
                            undoAction = true;
                            viewModel.insertWords(wordToData);
                        })
                        .show();
            }

            final Drawable icon = ContextCompat.getDrawable(requireActivity(), R.drawable.ic_baseline_delete_forever_24);
            final Drawable background = new ColorDrawable(Color.LTGRAY);
            @Override
            public void onChildDraw(@NonNull Canvas c, @NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, boolean isCurrentlyActive) {
                super.onChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive);
                View itemView = viewHolder.itemView;
                assert icon != null;
                int iconMargin = (itemView.getHeight() - icon.getIntrinsicHeight()) / 2;
                int iconStart, iconEnd, iconTop, iconBottom;
                int backStart, backEnd, backTop, backBottom;
                backTop = itemView.getTop();
                backBottom = itemView.getBottom();
                iconTop = itemView.getTop() + (itemView.getHeight() - icon.getIntrinsicHeight()) / 2;
                iconBottom = iconTop + icon.getIntrinsicHeight();
                if (dX > 0) {
                    backStart = itemView.getLeft();
                    backEnd = itemView.getLeft() + (int) dX;
                    background.setBounds(backStart, backTop, backEnd, backBottom);
                    iconStart = itemView.getLeft() + iconMargin;
                    iconEnd = iconStart + icon.getIntrinsicWidth();
                    icon.setBounds(iconStart, iconTop, iconEnd, iconBottom);
                } else if (dX < 0) {
                    backEnd = itemView.getRight();
                    backStart = itemView.getRight() + (int) dX;
                    background.setBounds(backStart, backTop, backEnd, backBottom);
                    iconEnd = itemView.getRight() - iconMargin;
                    iconStart = iconEnd - icon.getIntrinsicWidth();
                    icon.setBounds(iconStart, iconTop, iconEnd, iconBottom);
                } else {
                    background.setBounds(0, 0, 0, 0);
                    icon.setBounds(0, 0, 0, 0);
                }
                background.draw(c);
                icon.draw(c);
            }

        }).attachToRecyclerView(recyclerView);

        FloatingActionButton floatingActionButton = view.findViewById(R.id.floatingActionButton);
        floatingActionButton.setOnClickListener(view1 -> {
            NavController navController = Navigation.findNavController(view1);
            navController.navigate(R.id.action_wordsFragment_to_addFragment);
        });
    }
}

5. 创建添加词汇页

  5.1 添加词汇布局文件, fragment_add.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/addLayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".AddFragment" >

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="添加单词"
        android:textSize="24sp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.1" />

    <EditText
        android:id="@+id/et_english"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginEnd="16dp"
        android:ems="10"
        android:hint="English Word"
        android:inputType="textPersonName"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.2" />

    <EditText
        android:id="@+id/et_chinese"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:ems="10"
        android:hint="中文释义"
        android:inputType="textPersonName"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="@+id/et_english"
        app:layout_constraintStart_toStartOf="@+id/et_english"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.3" />

    <Button
        android:id="@+id/bt_submit"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:text="确定"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="@+id/et_english"
        app:layout_constraintStart_toStartOf="@+id/et_english"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.4" />
</androidx.constraintlayout.widget.ConstraintLayout>

  5.2 创建添加词汇页, AddFragment.java

public class AddFragment extends Fragment {
    private Button btSubmit;
    private EditText etEnglish, etChinese;
    private WordViewModel viewModel;
    private InputMethodManager imm;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        return inflater.inflate(R.layout.fragment_add, container, false);
    }

    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        FragmentActivity activity = requireActivity();
        btSubmit = view.findViewById(R.id.bt_submit);
        etEnglish = view.findViewById(R.id.et_english);
        etChinese = view.findViewById(R.id.et_chinese);
        btSubmit.setEnabled(false);
        etEnglish.requestFocus();
        imm = (InputMethodManager) activity.getSystemService(Context.INPUT_METHOD_SERVICE);
        imm.showSoftInput(etEnglish, 0);

        TextWatcher textWatcher = new TextWatcher() {
            @Override
            public void beforeTextChanged(CharSequence charSequence, int i, int i1, int i2) {
            }
            @Override
            public void onTextChanged(CharSequence charSequence, int i, int i1, int i2) {
                String english = etEnglish.getText().toString().trim();
                String chinese = etChinese.getText().toString().trim();
                btSubmit.setEnabled(!english.isEmpty() && !chinese.isEmpty());
            }

            @Override
            public void afterTextChanged(Editable editable) {
            }
        };
        etEnglish.addTextChangedListener(textWatcher);
        etChinese.addTextChangedListener(textWatcher);
        viewModel = new ViewModelProvider(activity).get(WordViewModel.class);
        btSubmit.setOnClickListener(view1 -> {
            String english = etEnglish.getText().toString().trim();
            String chinese = etChinese.getText().toString().trim();
            Word word = new Word(english, chinese);
            viewModel.insertWords(word);
            imm.hideSoftInputFromWindow(view1.getWindowToken(), 0);
            NavController navController = Navigation.findNavController(view1);
            navController.navigateUp();
        });
    }
}

6. 主页 Activity

  6.1 布局文件, activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <androidx.fragment.app.FragmentContainerView
        android:id="@+id/fragmentContainerView"
        android:name="androidx.navigation.fragment.NavHostFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:defaultNavHost="true"
        app:navGraph="@navigation/navigation" />
</androidx.constraintlayout.widget.ConstraintLayout>

  6.2 创建主页，MainActivity.java

public class MainActivity extends AppCompatActivity {
    NavController navController;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        NavHostFragment navHostFragment = (NavHostFragment) getSupportFragmentManager().findFragmentById(R.id.fragmentContainerView);
        assert navHostFragment != null;
        navController = navHostFragment.getNavController();
        NavigationUI.setupActionBarWithNavController(this, navController);
    }

    @Override
    public boolean onSupportNavigateUp() {
        navController.navigateUp();
        return super.onSupportNavigateUp();
    }

    @Override
    public void onBackPressed() {
        super.onBackPressed();
        navController.navigateUp();
    }
}

7. 效果图