在Android SQLITE数据库中存储新城市天气数据并更新现有城市天气数据

Question

我使用OpenWeatherMap API以JSON格式提取当前天气数据。

下面的数据是一个例子：

{"coord":{"lon":-83.05,"lat":42.33},"weather":[{"id":800,"main":"Clear","description":"clear sky","icon":"01d"}],"base":"stations","main":{"temp":48.1,"pressure":1004.19,"humidity":100,"temp_min":48.1,"temp_max":48.1,"sea_level":1028.21,"grnd_level":1004.19},"wind":{"speed":15.23,"deg":315.508},"clouds":{"all":0},"dt":1477154497,"sys":{"message":0.1743,"country":"US","sunrise":1477137281,"sunset":1477175856},"id":4990729,"name":"Detroit","cod":200} 
{"coord":{"lon":-87.65,"lat":41.85},"weather":[{"id":802,"main":"Clouds","description":"scattered clouds","icon":"03d"}],"base":"stations","main":{"temp":51.38,"pressure":1009.38,"humidity":100,"temp_min":51.38,"temp_max":51.38,"sea_level":1031.85,"grnd_level":1009.38},"wind":{"speed":8.08,"deg":227.508},"clouds":{"all":48},"dt":1477154834,"sys":{"message":0.1714,"country":"US","sunrise":1477138345,"sunset":1477177000},"id":4887398,"name":"Chicago","cod":200} 
{"coord":{"lon":-74.01,"lat":40.71},"weather":[{"id":500,"main":"Rain","description":"light rain","icon":"10d"}],"base":"stations","main":{"temp":48.14,"pressure":1008,"humidity":100,"temp_min":48.14,"temp_max":48.14,"sea_level":1011.38,"grnd_level":1008},"wind":{"speed":15.46,"deg":296.508},"rain":{"3h":2.2},"clouds":{"all":80},"dt":1477154848,"sys":{"message":0.1842,"country":"US","sunrise":1477134973,"sunset":1477173827},"id":5128581,"name":"New York","cod":200} 

作为可以在用户选择的任何时间删除“虚拟条目”，这三个城市被插入的onCreate（）（虽然现在我明白为什么能是一个坏主意）

我的意图是让这三个虚拟记录更新onCreate（）或onResume（）而不创建自己的新记录，然后将其添加到ListView。

添加新城市将拉取当前天气数据并将其添加到表格中，随后使用实时数据进行更新。

我的想法是在插入之前检查记录是否已经存在，而不是插入新条目，它会查找并设置新数据的温度和任何其他相关字段。

但我很笨，以及如何开始“检查”。这里是我的插入方法：

public void insertRow(CustomListData weather){ 
    SQLiteDatabase db = this.getWritableDatabase(); 
     ContentValues insertValues = new ContentValues(); 
     insertValues.put("TEMP", weather.getTemperature()); 
     insertValues.put("CITYNAME", weather.getCity()); 
     insertValues.put("ZIP", weather.getZip()); 
     db.insert("weather_data", null, insertValues); 
     db.close(); 
} 

编辑：

架构：

CREATE TABLE weather_data(_id INTEGER PRIMARY KEY AUTOINCREMENT, TEMP VARCHAR(5), CITYNAME VARCHAR(255), ZIP VARCHAR(6)); 

第二个编辑：

WeatherDataStorage -- helper class

Answer 1

如果需要检查，如果记录不存在在表格中，最快的方法是检查这种方式（假设邮政编码是所有记录）独特：

 public static boolean checkIfRecordExists(Context context, String tableName, 
           String tableAttribute, String attributeValue) { 

      Cursor cursor = context.getContentResolver().query(tableName, 
      new String[]{"1"}, 
      tableAttribute + "=?, 
      new String[]{attributeValue}, 
      null); 

      boolean recordExists = (cursor !=null && cursor.getCount() > 0); 
      cursor.close(); 

      return recordExists; 
    } 

所以，你可以调用此方法来检查，如果你的“weather_data”表中存在的记录。

public void insertRow(CustomListData weather){ 
SQLiteDatabase db = this.getWritableDatabase(); 

//(Context context, String tableName, String tableAttribute, String attributeValue) 

    boolean recordExists = checkIfRecordExists(context, "weather_data", "ZIP", weather.getZip()); 

    if(!recordExists) { 
     ContentValues insertValues = new ContentValues(); 
     insertValues.put("TEMP", weather.getTemperature()); 
     insertValues.put("CITYNAME", weather.getCity()); 
     insertValues.put("ZIP", weather.getZip()); 
     db.insert("weather_data", null, insertValues); 
     db.close(); 
    } 
} 

请尽量严格按照规范操作。您正试图检查表中的记录是否与邮政编码相关。

因此，当调用实用方法checkIfRecordExists与这些PARAMS checkIfRecordExists（上下文中， “weather_data”， “邮政编码”， “DUMMY_ZIP_1234”），

查询转换为选择1 FROM weather_data WHERE ZIP =“DUMMY_ZIP_1234”

您运行select查询，将结果保存在游标中，并检查游标是否保存任何记录。如果游标保存了一些记录，则表示记录已经存在。

PS：如果邮政编码是唯一的，请使用邮政编码作为你的“weather_data”表的主键