Android Room SQLite_ERROR 没有这样的表

Question

我正在尝试使用 Android Room并在关注 this tutorial 之后尝试构建应用程序时出现以下错误:

Error:(23, 27) error: 查询有问题:[SQLITE_ERROR] SQL错误或缺少数据库(没有这样的表:screen_items)

名称很好，应该存在。进行更改后，我清理了项目并确保它已从设备上完全卸载。

在我的 Activity 中，我正在用这一行初始化 onCreate 中的东西:

db = AppDatabase.getDatabase(getApplicationContext());

这是我的代码:

应用数据库

@Database(entities = {PermitItem.class}, version = 1, exportSchema = false)
public abstract class AppDatabase extends RoomDatabase {
  public static String DATABASE_NAME = "my_database";
  public final static String TABLE_ITEMS = "screen_items";

  private static AppDatabase INSTANCE;

  public abstract PermitItemDao permitItemModel();

  public static AppDatabase getDatabase(Context context) {
    if (INSTANCE == null) {
        INSTANCE = Room.databaseBuilder(context, AppDatabase.class, DATABASE_NAME).allowMainThreadQueries().build();
    }
    return INSTANCE;
  }

  public static void destroyInstance() {
    INSTANCE = null;
  }
}

PermitItem

@Entity
public class PermitItem {
  @PrimaryKey(autoGenerate = true)
  public final int id;
  private String posX, posY, width, height, content, type;

  public PermitItem(int id, String posX, String posY, String width, String height, String content, String type) {
    this.id = id;
    this.posX = posX;
    this.posY = posY;
    this.width = width;
    this.height = height;
    this.content = content;
    this.type = type;
  }

  public static PermitItemBuilder builder(){
    return new PermitItemBuilder();
  }

  public static class PermitItemBuilder{
    int id;
    String posX, posY, width, height, content, type;


    public PermitItemBuilder setId(int id) {
        this.id = id;
        return this;
    }


    public PermitItemBuilder setPosX(String posX) {
        this.posX = posX;
        return this;
    }


    public PermitItemBuilder setPosY(String posY) {
        this.posY = posY;
        return this;
    }


    public PermitItemBuilder setWidth(String width) {
        this.width = width;
        return this;
    }


    public PermitItemBuilder setHeight(String height) {
        this.height = height;
        return this;
    }


    public PermitItemBuilder setContent(String content) {
        this.content = content;
        return this;
    }


    public PermitItemBuilder setType(String type) {
        this.type = type;
        return this;
    }

    public PermitItem build() {
        return new PermitItem(id, posX, posY, width, height, content, type);
    }
  }

  public long getId() {
    return id;
  }

  public String getPosX() {
    return posX;
  }

  public void setPosX(String posX) {
    this.posX = posX;
  }

  public String getPosY() {
    return posY;
  }

  public void setPosY(String posY) {
    this.posY = posY;
  }

  public String getWidth() {
    return width;
  }

  public void setWidth(String width) {
    this.width = width;
  }

  public String getHeight() {
    return height;
  }

  public void setHeight(String height) {
    this.height = height;
  }

  public String getContent() {
    return content;
  }

  public void setContent(String content) {
    this.content = content;
  }

  public String getType() {
    return type;
  }

  public void setType(String type) {
    this.type = type;
  }

  @Override
  public String toString() {
    return "PermitItem{" +
            "id=" + id +
            ", posX='" + posX + '\'' +
            ", posY='" + posY + '\'' +
            ", width='" + width + '\'' +
            ", height='" + height + '\'' +
            ", content='" + content + '\'' +
            ", type='" + type + '\'' +
            '}';
  }


}

PermitItemDao

@Dao
public interface PermitItemDao {

  @Insert(onConflict = OnConflictStrategy.REPLACE)
  long addPermitItem(PermitItem permitItem);

  @Query("select * from " + TABLE_ITEMS)
  ArrayList<PermitItem> getAllPermitItems();

  @Query("select * from " + TABLE_ITEMS + " where id = :id")
  PermitItem getPermitItemById(int id);

  @Update(onConflict = OnConflictStrategy.REPLACE)
  void updatePermitItem(PermitItem permitItem);

  @Query("delete from " + TABLE_ITEMS)
  void removeAllPermitItems();
}

Answer 1

此错误的另一个原因可能是该实体未在 AppDatabase.java 文件中列出:

    @Database(entities = {XEntity.class, YEntity.class, ZEntity.class}, 
version = 1, exportSchema = true)

确保数据库文件夹中有最新的 db 文件，如果导出架构，请确保 app\schemas 下的 .json 架构文件正确更新。