4.4.5
1、創建CopntrolPoints類文件
2、引入必要到類
package com.nokia.example.location.tourist.model;
import Java.io.IOException;
import Java.util.Enumeration;
import Javax.microedition.location.Coordinates;
import Javax.microedition.location.Landmark;
import Javax.microedition.location.LandmarkException;
import Javax.microedition.location.LandmarkStore;
3、創建ControlPoints類，並定義類中使用的常量。LandmarkStore類用來從一個永久的路標庫中存儲、刪除、恢復一個路標。
關於這個類的更多信息，參考Location API。
/**
* Model class that handles landmark store actions.
*/
public class ControlPoints
{
private LandmarkStore store = null;
private static final String STORENAME = "TOURIST_DEMO";
private static final String DEFAULT_CATEGORY = null;
private static ControlPoints INSTANCE = null;
4、創建構架。createLandmarkStore方法重新創建了一個新的路標庫。當處理陸標發生錯誤的時候程序跳轉至LandmarkException。
/**
* Constructs instance of this class. Makes sure that landmark store
* instance exists.
*/
private ControlPoints()
{
String name = null;
// Try to find landmark store called "TOURIST_DEMO".
try
{
store = LandmarkStore.getInstance(STORENAME);
}
catch (NullPointerException npe)
{
// This should never occur.
}
// Check whether landmark store exists.
if (store == null)
{
// Landmark store does not exist.
try
{
// Try to create landmark store named "TOURIST_DEMO".
LandmarkStore.createLandmarkStore(STORENAME);
name = STORENAME;
}
catch (IllegalArgumentException iae)
{
// Name is too long or landmark store with the specifIEd
// name already exists. This Exception should not occur,
// because we have earlIEr tryed to created instance of
// this landmark store.
}
catch (IOException e)
{
// Landmark store couldn't be created due to an I/O error
}
catch (LandmarkException e)
{
// Implementation does not support creating new landmark
// stores.
}
store = LandmarkStore.getInstance(name);
}
}
5、創建一個獨有的getInstance方法
/**
* Singleton patterns getInstance method. Makes sure that only one instance
* of this class is alive at once.
*
* @return instance of this class.
*/
public static ControlPoints getInstance()
{
if (INSTANCE == null)
{
INSTANCE = new ControlPoints();
}
return INSTANCE;
}
6、創建一個方法，通過索引從路標庫中尋找陸標。Landmark類代表了一個陸標。
/**
* Find a Landmark from the landmark store using a index.
*
* @param index -
* the landmark in the store.
* @return Landmark from landmark store.
*/
public Landmark findLandmark(int index)
{
Landmark lm = null;
Enumeration cps = ControlPoints.getInstance().getLandMarks();
int counter = 0;
while (cps.hasMoreElements())
{
lm = (Landmark) cps.nextElement();
if (counter == index)
{
break;
}
counter++;
}
return lm;
}
7、用getLandmarks方法列舉庫中所有的陸標。
GetLatitude方法和getLongtitude方法將返回坐標的經度和緯度。getQualifIEdCoordinates方法將獲取陸標的QualifIEdCoordinate值。
/**
* Find nearest landmark to coordinate parameter from the landmarkstore.
*/
public Landmark findNearestLandMark(Coordinates coord)
{
Landmark landmark = null;
double latRadius = 0.1;
double lonRadius = 0.1;
float dist = Float.MAX_VALUE;
try
{
// Generate enumeration of Landmarks that are close to coord.
Enumeration enu = store.getLandmarks(null, coord.getLatitude()
- latRadius, coord.getLatitude() + latRadius, coord
.getLongitude() - lonRadius, coord.getLongitude()
+ lonRadius);
float tmpDist;
Landmark tmpLandmark = null;
while (enu.hasMoreElements())
{
tmpLandmark = (Landmark) enu.nextElement();
tmpDist = tmpLandmark.getQualifIEdCoordinates().distance(coord);
if (tmpDist < dist)
{
landmark = tmpLandmark;
}
}
}
catch (IOException ioe)
{
// I/O error happened when Accessing the landmark store.
return null;
}
return landmark;
}
public Enumeration getLandMarks()
{
Enumeration enu = null;
try
{
enu = store.getLandmarks();
}
catch (IOException ioe)
{
// I/O error happened when Accessing the landmark store.
}
return enu;
}
8、創建變量，用於類中方法的增加、更新、刪除。
public void addLandmark(Landmark landmark) throws IOException
{
store.addLandmark(landmark, DEFAULT_CATEGORY);
}
public void updateLandmark(Landmark landmark) throws IOException,
LandmarkException
{
store.updateLandmark(landmark);
}
public void removeLandmark(Landmark landmark) throws IOException,
LandmarkException
{
store.deleteLandmark(landmark);
}
