我正在尝试创建一个使用 GPS 的 BB 应用程序。
_screen 出现但 _status 没有改变（它总是说“等待位置更新”）。
我用新的 GPS（lugar）创建了对象，但它不起作用。其他 GPS 应用程序正常工作。
这是我的 BB 代码：
package mypackage;
import java.util.*;
import javax.microedition.location.*;
import data.Lugar;
import net.rim.device.api.gps.*;
import net.rim.device.api.system.*;
import net.rim.device.api.ui.*;
import net.rim.device.api.ui.component.*;
import net.rim.device.api.ui.container.*;
public class GPS
{
// Represents the number of updates over which altitude is calculated, in seconds
private static final int GRADE_INTERVAL = 5;
// com.rim.samples.device.gpsdemo.GPSDemo.ID
private static final long ID = 0x5d459971bb15ae7aL;
// Represents period of the position query, in seconds
private static int _interval = 1;
private static Vector _previousPoints;
private static float[] _altitudes;
private static float[] _horizontalDistances;
private static PersistentObject _store;
// Initialize or reload the persisted WayPoints
static
{
_store = PersistentStore.getPersistentObject(ID);
if(_store.getContents() == null)
{
_previousPoints = new Vector();
_store.setContents(_previousPoints);
}
_previousPoints = (Vector) _store.getContents();
}
private long _startTime;
private float _wayHorizontalDistance;
private float _horizontalDistance;
private float _verticalDistance;
private double latitud;
private double longitud;
private double latitud_anterior = 0;
private double longitud_anterior = 0;
private RichTextField status;
private EditField _status;
private LocationProvider _locationProvider;
private GPSDemoScreen _screen;
Lugar destino;
/**
* Create a new GPS object
*/
public GPS(Lugar l)
{
destino = l;
// Used by WayPoints, represents the time since the last waypoint
_startTime = System.currentTimeMillis();
_altitudes = new float[GRADE_INTERVAL];
_horizontalDistances = new float[GRADE_INTERVAL];
_screen = new GPSDemoScreen();
_screen.setTitle("GPS Demo");
_status = new EditField(Field.NON_FOCUSABLE);
status = new RichTextField("Obteniendo señal GPS...");
_screen.add(_status);
_screen.add(status);
// Attempt to start the location listening thread
if(startLocationUpdate())
{
_screen.setState(_locationProvider.getState());
}
// Render the screen
UiApplication.getUiApplication().pushScreen(_screen);
}
/**
* Update the GUI with the data just received
*
* @param msg The message to display
*/
private void updateLocationScreen(final String msg)
{
_status.setText(msg);
}
/**
* Invokes the Location API with Standalone criteria
*
* @return True if the <code>LocationProvider</code> was successfully started, false otherwise
*/
private boolean startLocationUpdate()
{
boolean returnValue = false;
if(GPSInfo.isGPSModeAvailable(GPSInfo.GPS_MODE_AUTONOMOUS))
{
try
{
Criteria criteria = new Criteria();
criteria.setCostAllowed(false);
_locationProvider = LocationProvider.getInstance(criteria);
if(_locationProvider != null)
{
/*
* Only a single listener can be associated with a provider,
* and unsetting it involves the same call but with null.
* Therefore, there is no need to cache the listener
* instance request an update every second.
*/
_locationProvider.setLocationListener(new LocationListenerImpl(), _interval, -1, -1);
returnValue = true;
}
else
{
Dialog.alert("Failed to obtain a location provider, exiting...");
System.exit(0);
}
}
catch(final LocationException le)
{
Dialog.alert("Failed to instantiate LocationProvider object, exiting..." + le.toString());
System.exit(0);
}
}
else
{
Dialog.alert("GPS autonomous/standalone mode is not supported on this device, exiting...");
System.exit(0);
}
return returnValue;
}
/**
* Implementation of the LocationListener interface. Listens for updates to
* the device location and displays the results.
*/
private class LocationListenerImpl implements LocationListener
{
/**
* @see javax.microedition.location.LocationListener#locationUpdated(LocationProvider,Location)
*/
public void locationUpdated(LocationProvider provider, Location location)
{
if(location.isValid())
{
float heading = location.getCourse();
longitud = location.getQualifiedCoordinates().getLongitude();
latitud = location.getQualifiedCoordinates().getLatitude();
float altitude = location.getQualifiedCoordinates().getAltitude();
float speed = location.getSpeed();
// Horizontal distance for current Location
float horizontalDistance = speed * _interval;
_horizontalDistance += horizontalDistance;
// Horizontal distance for WayPoint
_wayHorizontalDistance += horizontalDistance;
// Distance over the current interval
float totalDist = 0;
// Moving average grade
for(int i = 0; i < GRADE_INTERVAL - 1; ++i)
{
_altitudes[i] = _altitudes[i + 1];
_horizontalDistances[i] = _horizontalDistances[i + 1];
totalDist = totalDist + _horizontalDistances[i];
}
_altitudes[GRADE_INTERVAL - 1] = altitude;
_horizontalDistances[GRADE_INTERVAL - 1] = speed * _interval;
totalDist = totalDist + _horizontalDistances[GRADE_INTERVAL - 1];
float grade = (totalDist == 0.0F) ? Float.NaN : ((_altitudes[4] - _altitudes[0]) * 100 / totalDist);
// Running total of the vertical distance gain
float altGain = _altitudes[GRADE_INTERVAL - 1] - _altitudes[GRADE_INTERVAL - 2];
if(altGain > 0)
{
_verticalDistance = _verticalDistance + altGain;
}
// Information to be displayed on the device
StringBuffer sb = new StringBuffer();
sb.append("Longitude: ");
sb.append(longitud);
sb.append("\n");
sb.append("Latitude: ");
sb.append(latitud);
sb.append("\n");
sb.append("Grade : ");
if(Float.isNaN(grade))
{
sb.append(" Not available");
}
else
{
sb.append(grade + " %");
}
GPS.this.updateLocationScreen(sb.toString());
//... other things non related to GPS
}
}
public void providerStateChanged(LocationProvider provider, int newState)
{
if(newState == LocationProvider.TEMPORARILY_UNAVAILABLE)
{
provider.reset();
}
_screen.setState(newState);
}
}
/**
* The main screen to display the current GPS information
*/
private final class GPSDemoScreen extends MainScreen
{
TextField _statusTextField;
/**
* Create a new GPScreen object
*/
GPScreen()
{
// Initialize UI
_statusTextField = new TextField(Field.NON_FOCUSABLE);
_statusTextField.setLabel("GPS Status: ");
add(_statusTextField);
RichTextField instructions = new RichTextField("Waiting for location update...", Field.NON_FOCUSABLE);
add(instructions);
}
public void setState(final int newState)
{
UiApplication.getUiApplication().invokeLater(new Runnable()
{
public void run()
{
switch(newState)
{
case LocationProvider.AVAILABLE:
_statusTextField.setText("Available");
break;
case LocationProvider.OUT_OF_SERVICE:
_statusTextField.setText("Out of Service");
break;
case LocationProvider.TEMPORARILY_UNAVAILABLE:
_statusTextField.setText("Temporarily Unavailable");
break;
}
}
});
}
/**
* @see net.rim.device.api.ui.Screen#close()
*/
public void close()
{
if(_locationProvider != null)
{
_locationProvider.reset();
_locationProvider.setLocationListener(null, -1, -1, -1);
}
super.close();
}
}
}