创建一个SQLite数据库来存储Geopoints并将它们读到MapActivity上

Question

我正在尝试创建一个Map活动，并且我已经能够成功地从主活动中读取一个静态坐标字符串，但是这是硬编码的，我希望您将这些坐标插入到SQLite数据库中并且他们被阅读。 我试过环顾四周但我无法得到我正在寻找的答案，如果有人可以帮助我，我会很感激

继承我的主要活动 - GMapsActivity.java：

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

    mapView = (MapView)findViewById(R.id.map_view);
    mapView.setBuiltInZoomControls(true);
    //mapView.setStreetView(true);
    mapController = mapView.getController();

    String coordinates[] = {"51.52241608253253","-0.1318359375"};
    double lat = Double.parseDouble(coordinates[0]);
    double lng = Double.parseDouble(coordinates[1]);
    GeoPoint general = new GeoPoint((int) (lat * 1E6), (int) (lng * 1E6) );
    mapController.setZoom(10);
    mapController.animateTo(general);

    mapOverlays = mapView.getOverlays();
    drawable = this.getResources().getDrawable(R.drawable.blue);
    itemizedOverlay = new NewItemizedOverlay(drawable, this);

    GeoPoint point = new GeoPoint((int)(51.555890943494276*1E6), (int)(-0.39989858865737915*1E6));
    OverlayItem overlayitem = new OverlayItem(point, "Greenword Veterinary" , "57 Station Approach, South Ruislip, Ruislip, Middlesex, HA4 6SL, 020 8845 8144");
    itemizedOverlay.addOverlay(overlayitem);

    GeoPoint point2 = new GeoPoint((int)(51.598707*1E6), (int)(-0.393416*1E6));
    OverlayItem overlayitem2 = new OverlayItem(point2, "MediVet Pinner" , "2A Pinner Green, Pinner, Middlesex, HA5 2AA, 020 8866 0727");
    itemizedOverlay.addOverlay(overlayitem2);

    GeoPoint point3 = new GeoPoint((int)(51.670865*1E6), (int)(-0.397034*1E6));
    OverlayItem overlayitem3 = new OverlayItem(point3, "MediVet Watford" , "237 Saint Albans Road, Watford, Hertfordshire WD24 5BP, 01923 243 429");
    itemizedOverlay.addOverlay(overlayitem3);
    mapOverlays.add(itemizedOverlay);

    myLocationOverlay = new MyLocationOverlay(this, mapView);
    mapView.getOverlays().add(myLocationOverlay);

这是我的数据库创建者 - DatabaseManager.java

package com.javacodegeeks.android.googlemaps;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;

public class DatabaseManager {

public static final String KEY_ID = "_id";
public static final String KEY_LAT = "vetlat";
public static final String KEY_LONGI = "vetlongi";
public static final String KEY_NAME = "vetname";
public static final String KEY_INFO = "vetinfo";

private static final String DATABASE_NAME = "myvet.db";
private static final String DATABASE_TABLE = "vetLocations";
private static final int DATABASE_VERSION = 1;

private DbHelper ourHelper;
private final Context ourContext;
private SQLiteDatabase ourDB;

private static class DbHelper extends SQLiteOpenHelper
{

    public DbHelper(Context context) 
    {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
        // TODO Auto-generated constructor stub
    }

    @Override
    public void onCreate(SQLiteDatabase db) 
    {
        // TODO Auto-generated method stub
        db.execSQL("CREATE TABLE " + DATABASE_TABLE + " (" + 
                KEY_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " + 
                KEY_LAT + "REAL NOT NULL," + 
                KEY_LONGI + "REAL NOT NULL," +
                KEY_NAME + "TEXT NOT NULL," +
                KEY_INFO + "TEXT NOT NULL);"
        );
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // TODO Auto-generated method stub
        db.execSQL("DROP TABLE IF EXISTS " + DATABASE_TABLE);
        onCreate(db);
    }

}

public DatabaseManager(Context c)
{
    ourContext = c;
}

public DatabaseManager open()
{
    ourHelper = new DbHelper(ourContext);
    ourDB = ourHelper.getReadableDatabase();
    return this;
}

public void close()
{
    ourHelper.close();
}

}

我是Android编程的新手，所以我很感激有人能真正向我展示代码片段，而不是一般的指示，因为我真的不了解它们大声笑

编辑： 我在SQLite浏览器中创建了数据库条目 我怎样才能使主活动文件读取该文件中的值？

一般认为代码会尝试调用以下值： SELECT * FROM DB 放入数组 然后循环它

points = ((int)([lat_value_from_db1*E6]), ((int)([longi_value_from_db1*E6]);
overlay = (points, [name_value_from_db], [info_value_from_db]);
itemizedOverylay.addOverlay(allOverlays);

我真的不确定如何实现这个：/

我非常感谢任何形式的帮助

提前谢谢

Answer 1

首先，创建一个类作为数据库记录DatabaseObject.java的对象：

public class DatabaseObject {

       int _id;
       double _lat;
       double _lng;
       String _name;
       String _info;

        // Empty constructor
        public DatabaseObject(){

        }
        // constructor
        public DatabaseObject(int id, double lat, double lng,String name ,String info){
            this._id = id;
            this._lat=lat;
            this._lng=lng;
            this._name=name;
            this._info=info;
        }
        public DatabaseObject(double lat, double lng,String name ,String info){
             this._lat=lat;
                this._lng=lng;
                this._name=name;
                this._info=info;
        }
        // constructor

        // getting ID
        public int getID(){
            return this._id;
        }

        // setting id
        public void setID(int id){
            this._id = id;
        }


        public double getlat(){
            return this._lat;
        }

        public void setlat(double lat){
            this._lat = lat;
        }

        public double getlng(){
            return this._lng;
        }

        public void setlng(double lng){
            this._lng = lng;
        }

        public String getname(){
            return this._name;
        }

        // setting id
        public void setname(String name){
            this._name = name;
        }

        public String getinfo(){
            return this._info;
        }

        // setting id
        public void setinfo(String info){
            this._infor= info;
        }   
}

然后在DatabaseManager.java：

中添加这两个功能

// Getting one database object by id
public DatabaseObject get_DatabaseObject(int id) {
       SQLiteDatabase db = this.getReadableDatabase();

        Cursor cursor = db.query(TABLE_NAME, new String[] { KEY_ID,
                KEY_LAT, KEY_LONGI,KEY_NAME,KEY_INFO }, KEY_ID + "=?",
                new String[] { String.valueOf(id) }, null, null,null,null);
        if (cursor != null)
            cursor.moveToFirst();

        DatabaseObject data = new DatabaseObject(Integer.parseInt(cursor.getString(0)),
                Double.parseDouble(cursor.getString(1)), Double.parseDouble(cursor.getString(2)),cursor.getString(3), cursor.getString(4));
        // return database object
       return data;
   }

    // Getting All database objects
    public List<DatabaseObject> getAllDatabaseObject() {
        List<DatabaseObject> contactList = new ArrayList<DatabaseObject>();
       //  Select All Query
        String selectQuery = "SELECT  * FROM " + TABLE_NAME;

        SQLiteDatabase db = this.getWritableDatabase();
        Cursor cursor = db.rawQuery(selectQuery, null);

        // looping through all rows and adding to list
        if (cursor.moveToFirst()) {
           do {
               DatabaseObject data = new DatabaseObject();
               data.setID(Integer.parseInt(cursor.getString(0)));
                data.setLAT( Double.parseDouble(cursor.getString(1)));
                data.setLONGI( Double.parseDouble(cursor.getString(2)));
                data.setNAME(cursor.getString(3));
               data.setINFO(cursor.getString(4));

              //   Adding contact to list
               contactList.add(data);
            } while (cursor.moveToNext());
        }

        // return database object list
       return dataList;
    }

现在在以下任何活动中使用这些：

1-将此声明为全局变量：

DatabaseManager db = new DatabaseManager(this);

2-检索所有对象：

List<DatabaseObject> K = db.getAllDatabaseObject(); 

3-以循环方式使用它：

for (DatabaseObject cn : K) {
        point = new GeoPoint((int)(cn.getlat()*E6), (int)(cn.getlng()*E6));
        overlayitem = new OverlayItem(point, cn.getname(), cn.getinfo());
        itemizedOverlay.addOverlay(overlayitem);
        mapOverlays.add(itemizedOverlay);
}