ROOM

ROOM對Sqlite進行了封裝，直接使用ROOM來進行數(shù)據(jù)庫訪問。

代碼：https://github.com/Gong-Shijie/RoomDemo

ROOM數(shù)據(jù)庫查詢可以直接返回LiveData對象，每次CRUD都會自動更新該LiveData，LiveData始終是數(shù)據(jù)庫最新值

利用該特性可以直接將數(shù)據(jù)庫的變化，通過LiveData作為觀察者傳遞到ViewModel，保證拿到的數(shù)據(jù)都是數(shù)據(jù)庫中時刻最新的值

使用流程：

Entry類-->Dao-->EntryRoomDatabase(單例模式)-->Repository(從EntryRoomDatabase獲得Dao)-->在Repository中實現(xiàn)異步-->AndroidViewModel通過Repository訪問數(shù)據(jù)庫CRUD

資料：https://codelabs.developers.google.com/codelabs/android-room-with-a-view/index.html?index=..%2F..index#0

框架

詳細設(shè)計

主要角色

• Entry 實體類
• Dao 定義接口數(shù)據(jù)庫操作
• 繼承RoomDatabase 通過ROOM實例化database返回Dao供調(diào)用
• 異步類調(diào)用Dao中數(shù)據(jù)庫操作如AsyncTask
• Repository對操作進行封裝
• AndroidViewModel 聚合 Repository來執(zhí)行數(shù)據(jù)庫操作

使用方法

工程結(jié)構(gòu)

代碼實現(xiàn)

Entry

@Entity
public class Word {
    @PrimaryKey(autoGenerate = true)
    private int id;
    @ColumnInfo(name = "english")
    private String english;
    @ColumnInfo(name = "chinese")
    private String mean;
    public Word(String english, String mean) {
        this.english = english;
        this.mean = mean;
    }
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getEnglish() {
        return english;
    }
    public void setEnglish(String english) {
        this.english = english;
    }
    public String getMean() {
        return mean;
    }
    public void setMean(String mean) {
        this.mean = mean;
    }
}

Dao

@Dao
public interface WordDao {
    @Insert
    void insertWord(Word... words);

    @Update
    void update(Word... words);
    @Delete
    void delete(Word... words);
    @Query("DELETE FROM WORD")
    void deleteAll();
    @Query("SELECT * FROM WORD ORDER BY ID DESC")
    LiveData<List<Word>> getAll();
}

WordRoomDatabase

@Database(entities = {Word.class},version = 1,exportSchema = false)
public abstract  class WordRoomDatabase extends RoomDatabase {
    public abstract WordDao getWordDao();
    private static  WordRoomDatabase INSTANCE;
    public  static  WordRoomDatabase getInstance(final Context context) {
        if (INSTANCE == null) {
            synchronized (WordRoomDatabase.class) {
                if (INSTANCE == null) {
                    INSTANCE = Room.databaseBuilder(context.getApplicationContext(),
                            WordRoomDatabase.class, "word_database")
                            .build();
                }
            }
        }
        return INSTANCE;
    }
}

Repository

public class Repository {
    private LiveData<List<Word>> wordsLive;

    public LiveData<List<Word>> getWordsLive() {
        return wordsLive;
    }

    //用來調(diào)用數(shù)據(jù)庫操作
    private WordDao wordDao;

    public Repository(Context context) {
        WordRoomDatabase wordRoomDatabase = WordRoomDatabase.getInstance(context.getApplicationContext());
        wordDao = wordRoomDatabase.getWordDao();
        wordsLive = wordDao.getAll();
    }
   public   void insert(Word... words){
        new InsertTask(wordDao).execute(words);
    }
   public    void delete(Word... words){
        new DeleteTask(wordDao).execute(words);
    }
   public    void update(Word... words){
        new UpdateTask(wordDao).execute(words);
    }
   public   void deleteAll(){
        new DeleteAllTask(wordDao).execute();
    }
}

VeiwModel

public class MainViewModel extends AndroidViewModel {
    // ViewModel 沒有很好的方法來獲得一個Context 需要繼承AndroidViewModel
    Repository repository;
    public MainViewModel(Application application) {
        super(application);
        this.repository = new Repository(application);
    }
  public   LiveData<List<Word>> getAll(){
        return repository.getWordsLive();
    }
   public void insert(Word... words){
        repository.insert(words);
    }
   public void update(Word... words){
        repository.update(words);
    }
   public void delete(Word... words){
        repository.delete(words);
    }
   public void deleteAll(){
        repository.deleteAll();
    }
}

總結(jié)

總結(jié)