高德天气应用开发之十三：android room数据库天气数据读写使用方法

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1. 请支持原创，转载请注明出处：https://blog.csdn.net/cbk861110/article/details/86665564

2. 项目源码请移步：https://github.com/caobaokang419/WeatherApp（欢迎Github Fork&Star，框架和技术实现不妥之处，请帮忙指正），谢谢！

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基于MVVM框架的高德天气APP：

MVVM框架和组件实现：

Room：一个简单好用的对象映射层；其对SqliteDatabase进行了封装，简化开发者对于数据持久层的开发工作量

一、技术背景：

room，Android推荐的DB实现库，使用库提供的大量注解自动生成相关DB类和代码，极大简化应用开发DB模块代码量；

二、实现方式（以高德城市配置表DB为例）：

1. gradle中集成Room jar：

implementation "android.arch.persistence.room:runtime:1.0.0"
implementation "android.arch.persistence.room:rxjava2:1.0.0"
annotationProcessor "android.arch.persistence.room:compiler:1.0.0"

2. room table表实现：

@Entity(tableName = CityInfoEntity.TABLE_NAME)
public class CityInfoEntity {
    public static final String TABLE_NAME = "city_info";

    @PrimaryKey
    public long id;

    @ColumnInfo(name = "city_name")
    public String city_name;

    @ColumnInfo(name = "adcode")
    public String adcode;

    public void setCityName(String cityname) {
        city_name = cityname;
    }

    public String getCityName() {
        return city_name;
    }

    public void setAdcode(String adcode) {
        this.adcode = adcode;
    }

    public String getAdcode() {
        return adcode;
    }
}

3. room DAO 实现：

@Dao
public interface CityInfoDAO {
    @Query("SELECT * FROM " + CityInfoEntity.TABLE_NAME)
    List<CityInfoEntity> getAll();

    @Query("SELECT * FROM " + CityInfoEntity.TABLE_NAME + " WHERE id IN (:ids)")
    List<CityInfoEntity> getAllByIds(long[] ids);

    @Insert
    void insert(CityInfoEntity... entities);

    @Delete
    void delete(CityInfoEntity entity);

    @Update
    void update(CityInfoEntity entity);
}

4. room database 实现：

@Database(entities = {CityForecastEntity.class, CityInfoEntity.class}, version = 1, exportSchema = false)
public abstract class WtDatabase extends RoomDatabase {
    public static final String WEATHER_DB_NAME = "weather_db";
    private static WtDatabase mWtDatabase;
    private static final Object mLock = new Object();

    /*城市天气数据DB*/
    public abstract CityForecastDAO cityForecastDAO();

    /*城市配置表DB*/
    public abstract CityInfoDAO cityInfoDAO();

    @Override
    public void clearAllTables() {

    }

    public static WtDatabase getInstance(Context context) {
        synchronized (mLock) {
            if (mWtDatabase == null) {
                mWtDatabase =
                        Room.databaseBuilder(context.getApplicationContext(),
                                WtDatabase.class,
                                WtDatabase.WEATHER_DB_NAME)
                                /*.allowMainThreadQueries()*//*db 耗时不应在UI线程发起*/
                                .build();
            }
            return mWtDatabase;
        }
    }
}

5. room 使用方法举例（插入cityinfo data item）：

private void insertCityInfo(CityInfoEntity entity) {
    WtDatabase.getInstance(WtApplication.getInstance()).cityInfoDAO().insert(entity);
}

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文章目录（未完，待续）：

一：android 应用子功能及移动框架总述 https://blog.csdn.net/cbk861110/article/details/86665564

二：android 高德天气API说明及城市天气查询实现 https://blog.csdn.net/cbk861110/article/details/86665655

三：android 自定义控件实现(ActionBar + PageIndicatorView) https://blog.csdn.net/cbk861110/article/details/86665790

四：android ViewPager实现左右页面滑动切换 https://blog.csdn.net/cbk861110/article/details/86665964

五：android应用权限动态申请 https://blog.csdn.net/cbk861110/article/details/86666321

六：android RecyclerView 封装及使用 https://blog.csdn.net/cbk861110/article/details/86666392

七：android Xutils3文件下载实现（高德天气城市配置） https://blog.csdn.net/cbk861110/article/details/86666573

八：android DiskLruCache 磁盘缓存封装和使用 https://blog.csdn.net/cbk861110/article/details/86666664

九：android ThreadPoolExecutor线程池封装及使用 https://blog.csdn.net/cbk861110/article/details/86667101

十：android 天气网络请求框架(retrofit2&okhttp3&Gson) 封装及使用 https://blog.csdn.net/cbk861110/article/details/86667375

十一：android RxAndroid(响应式编程) 异步网络请求实现 https://blog.csdn.net/cbk861110/article/details/86669178

十二：android DataBinding 数据和UI双向绑定实现 https://blog.csdn.net/cbk861110/article/details/86669708

十三：android room数据库天气数据读写实现 https://blog.csdn.net/cbk861110/article/details/86670354

十四：android LiveData 使用方法（实现城市天气自动刷新） https://blog.csdn.net/cbk861110/article/details/86670531

十五：android ViewModel 使用方法 https://blog.csdn.net/cbk861110/article/details/86670703

十六：android 集成友盟消息推送机制（U-Push） https://blog.csdn.net/cbk861110/article/details/86683849

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【版权说明】

1. 请支持原创，转载请注明出处：https://blog.csdn.net/cbk861110/article/details/86665564

2. 项目源码请移步：https://github.com/caobaokang419/WeatherApp（欢迎Github Fork&Star，框架和技术实现不妥之处，请帮忙指正），谢谢！