Question

我已经完成了使用SQLite，但我无法存储值。我通过ListView检索值来检查这一点。有人可以帮忙吗？我很震惊这个项目。

package com.mahesh.map2;
public class history extends ListActivity {

    //private static final String DATABASE_TABLE = null;

    private ArrayList<String> results = new ArrayList<String>();
    // private static final String DATABASE_TABLE = "locations";

    private static String DBNAME = "locationmarkersqlite";

    /** Field 1 of the table locations, which is the primary key */
    public static final String FIELD_ROW_ID = "_id";

    /** Field 2 of the table locations, stores the latitude */
    public static final String FIELD_LAT = "lat";

    /** Field 3 of the table locations, stores the longitude*/
    public static final String FIELD_LNG = "lng";

    /** Field 4 of the table locations, stores the zoom level of map*/
    public static final String FIELD_ZOOM = "zom";

    /** A constant, stores the the table name */
    private static final String DATABASE_TABLE = "locations";

    /** An instance variable for SQLiteDatabase */
    private SQLiteDatabase mDB;  

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        openAndQueryDatabase();

        displayResultList();


    }
    private void displayResultList() {
        TextView tView = new TextView(this);
        tView.setText("This data is retrieved from the database and only 4 " +
                "of the results are displayed");
        getListView().addHeaderView(tView);

        setListAdapter(new ArrayAdapter<String>(this,
                android.R.layout.simple_list_item_1, results));
        getListView().setTextFilterEnabled(true);

    }
    private void openAndQueryDatabase() {
        try {
            LocationsDB dbHelper = new LocationsDB(this.getApplicationContext());
            mDB = dbHelper.getWritableDatabase();
            //double latitude;
            //double longitude;
            Cursor c = mDB.query("locations", new String[]{
                     "latitude", "longitude"}, null, null,
                    null, null, null);
            if (c != null ) {
                if  (c.moveToFirst()) {
                    do {
                    //  String title = c.String(c
                     //           .getColumnIndex("title"));
                     //   String description = c.String(c
                      //          .getColumnIndex("description"));
                        int latitude = (int) (c.getDouble(c
                                .getColumnIndex("latitude")) * 1E6);
                        int longitude = (int) (c.getDouble(c
                                .getColumnIndex("longitude")) * 1E6);
                        results.add("FIELD_LNG" + latitude + ",FIELD_LAT " + longitude);
                    }while (c.moveToNext());
                } 
            }           
        } catch (SQLiteException e ) {
            Log.e(getClass().getSimpleName(), "Could not create or Open the database");
        } finally {
            if (mDB != null) 
                mDB.execSQL("DELETE FROM " + DATABASE_TABLE);
                mDB.close();
        }

    }

}

Answer 1

我正在使用ORMLite库来管理Db的东西。它很容易实现，不应超过4小时，但将来会非常有价值。首先，您必须创建一些要存储在db中的对象并添加注释，以便ORMLite知道存储的内容和方式。

public class MyTableRow {
    @DatabaseField
    long longitude;
    @DatabaseField
    long latitude;
    @DatabaseField(id=true)
    int id;
    public MyTableRow(long lon,long lat){..};
}

之后，创建连接源：

MySqliteOpenHelper dbHelper = null;
                AndroidConnectionSource connectionSource = null;
                if (dbHelper == null || connectionSource == null) {
                    dbHelper = new MySqliteOpenHelper(context, null, null,
                            0);
                    connectionSource = new AndroidConnectionSource(dbHelper);
                }

MySqliteOpenHelper可以是一个简单的配置类，具有数据库名称和版本：

public class MySqliteOpenHelper extends OrmLiteSqliteOpenHelper {

private static final String DATABASE_NAME = "test";
private static final int DATABASE_VERSION = 2;

public MySqliteOpenHelper(Context context, String databaseName,
        CursorFactory factory, int databaseVersion) {
    super(context, DATABASE_NAME, factory, DATABASE_VERSION);
    // TODO Auto-generated constructor stub
}

@Override
public void onCreate(SQLiteDatabase db, ConnectionSource connectionSource) {

}

@Override
public void onUpgrade(SQLiteDatabase database,
        ConnectionSource connectionSource, int oldVersion, int newVersion) {
    // TODO Auto-generated method stub

}
}

设置好后，您可以开始创建表格并插入和检索数据：

public static void createTables(ConnectionSource connectionSource,
        Class<?>... classes) {
    for (Class<?> c : classes) {
        try {
            TableUtils.createTableIfNotExists(connectionSource, c);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}
private static <T> void doInserts(ConnectionSource connectionSource,
        Class<T> object, List<T> objects)
        throws SQLException {
            final Dao<T, String> dao = DaoManager.createDao(connectionSource,
            object);

    for (T data : objects) {
        dao.createOrUpdate(data);
    }

}
public static <T> List<T> getTable(Class<T> objectClass,
        Context context) {
    MySqliteOpenHelper sqliteDbHelper = new MySqliteOpenHelper(context,
            null, null, 0);
    ConnectionSource connectionSource = new AndroidConnectionSource(
            sqliteDbHelper);

    List<T> mList;
    try {
        Dao<T, String> mDao = DaoManager.createDao(connectionSource,
                objectClass);
            mList = mDao.queryForAll();
        return mList;
    } catch (SQLException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IllegalStateException e) {
        e.printStackTrace();
    }
    return null;
}

如何在数据库中存储纬度和经度详细信息，并在ListView中检索详细信息

1 个答案: