java類在位置更新時回叫活動

Question

我發現這個類我想用來獲取位置更新，但我試圖找出位置更新時如何實現回調活動。 我是否使用一些回調或其他類型的方法來實現這個？

注意到我的代碼http://www.androidhive.info/2012/07/android-gps-location-manager-tutorial/

GPSTracker.java 
package com.example.gpstracking; 

import android.app.AlertDialog; 
import android.app.Service; 
import android.content.Context; 
import android.content.DialogInterface; 
import android.content.Intent; 
import android.location.Location; 
import android.location.LocationListener; 
import android.location.LocationManager; 
import android.os.Bundle; 
import android.os.IBinder; 
import android.provider.Settings; 
import android.util.Log; 

public class GPSTracker extends Service implements LocationListener { 

    private final Context mContext; 

    // flag for GPS status 
    boolean isGPSEnabled = false; 

    // flag for network status 
    boolean isNetworkEnabled = false; 

    // flag for GPS status 
    boolean canGetLocation = false; 

    Location location; // location 
    double latitude; // latitude 
    double longitude; // longitude 

    // The minimum distance to change Updates in meters 
    private static final long MIN_DISTANCE_CHANGE_FOR_UPDATES = 10; // 10 meters 

    // The minimum time between updates in milliseconds 
    private static final long MIN_TIME_BW_UPDATES = 1000 * 60 * 1; // 1 minute 

    // Declaring a Location Manager 
    protected LocationManager locationManager; 

    public GPSTracker(Context context) { 
     this.mContext = context; 
     getLocation(); 
    } 

    public Location getLocation() { 
     try { 
      locationManager = (LocationManager) mContext 
        .getSystemService(LOCATION_SERVICE); 

      // getting GPS status 
      isGPSEnabled = locationManager 
        .isProviderEnabled(LocationManager.GPS_PROVIDER); 

      // getting network status 
      isNetworkEnabled = locationManager 
        .isProviderEnabled(LocationManager.NETWORK_PROVIDER); 

      if (!isGPSEnabled && !isNetworkEnabled) { 
       // no network provider is enabled 
      } else { 
       this.canGetLocation = true; 
       // First get location from Network Provider 
       if (isNetworkEnabled) { 
        locationManager.requestLocationUpdates(
          LocationManager.NETWORK_PROVIDER, 
          MIN_TIME_BW_UPDATES, 
          MIN_DISTANCE_CHANGE_FOR_UPDATES, this); 
        Log.d("Network", "Network"); 
        if (locationManager != null) { 
         location = locationManager 
           .getLastKnownLocation(LocationManager.NETWORK_PROVIDER); 
         if (location != null) { 
          latitude = location.getLatitude(); 
          longitude = location.getLongitude(); 
         } 
        } 
       } 
       // if GPS Enabled get lat/long using GPS Services 
       if (isGPSEnabled) { 
        if (location == null) { 
         locationManager.requestLocationUpdates(
           LocationManager.GPS_PROVIDER, 
           MIN_TIME_BW_UPDATES, 
           MIN_DISTANCE_CHANGE_FOR_UPDATES, this); 
         Log.d("GPS Enabled", "GPS Enabled"); 
         if (locationManager != null) { 
          location = locationManager 
            .getLastKnownLocation(LocationManager.GPS_PROVIDER); 
          if (location != null) { 
           latitude = location.getLatitude(); 
           longitude = location.getLongitude(); 
          } 
         } 
        } 
       } 
      } 

     } catch (Exception e) { 
      e.printStackTrace(); 
     } 

     return location; 
    } 

    /** 
    * Stop using GPS listener 
    * Calling this function will stop using GPS in your app 
    * */ 
    public void stopUsingGPS(){ 
     if(locationManager != null){ 
      locationManager.removeUpdates(GPSTracker.this); 
     } 
    } 

    /** 
    * Function to get latitude 
    * */ 
    public double getLatitude(){ 
     if(location != null){ 
      latitude = location.getLatitude(); 
     } 

     // return latitude 
     return latitude; 
    } 

    /** 
    * Function to get longitude 
    * */ 
    public double getLongitude(){ 
     if(location != null){ 
      longitude = location.getLongitude(); 
     } 

     // return longitude 
     return longitude; 
    } 

    /** 
    * Function to check GPS/wifi enabled 
    * @return boolean 
    * */ 
    public boolean canGetLocation() { 
     return this.canGetLocation; 
    } 

    /** 
    * Function to show settings alert dialog 
    * On pressing Settings button will lauch Settings Options 
    * */ 
    public void showSettingsAlert(){ 
     AlertDialog.Builder alertDialog = new AlertDialog.Builder(mContext); 

     // Setting Dialog Title 
     alertDialog.setTitle("GPS is settings"); 

     // Setting Dialog Message 
     alertDialog.setMessage("GPS is not enabled. Do you want to go to settings menu?"); 

     // On pressing Settings button 
     alertDialog.setPositiveButton("Settings", new DialogInterface.OnClickListener() { 
      public void onClick(DialogInterface dialog,int which) { 
       Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS); 
       mContext.startActivity(intent); 
      } 
     }); 

     // on pressing cancel button 
     alertDialog.setNegativeButton("Cancel", new DialogInterface.OnClickListener() { 
      public void onClick(DialogInterface dialog, int which) { 
      dialog.cancel(); 
      } 
     }); 

     // Showing Alert Message 
     alertDialog.show(); 
    } 

    @Override 
    public void onLocationChanged(Location location) { 
    } 

    @Override 
    public void onProviderDisabled(String provider) { 
    } 

    @Override 
    public void onProviderEnabled(String provider) { 
    } 

    @Override 
    public void onStatusChanged(String provider, int status, Bundle extras) { 
    } 

    @Override 
    public IBinder onBind(Intent arg0) { 
     return null; 
    } 

} 

Answer 1

是的，你應該添加一個回調方法這樣的：

public GPSTracker(Context context, Activity calleractivity) { 
    this.mContext = context; 
    getLocation(); 

    this.calleractivity=calleractivity 
} 

而且你更新的方法是像

public void update(){ 
     calleractivity.getback(); 
    } 

而在你的活動：

gps = new GPSTracker(Context context, this); 

我希望它可以幫助

Answer 2

一些注意事項：

• 服務默認UI線程上運行。如果從特定源獲取位置需要很長時間，此類可能會阻止您的UI。你多久需要更新一次？您可以運行計時器向IntentService發送請求以獲取GPS信息。
• 如果你真的需要GPS「跟蹤」，那麼你做的是正確的事情，但請記住，GPS快速消耗電池。
• 從一個Android組件與另一個Android組件進行通信的最佳方式是使用BroadcastReceiver。這提供了清晰，直接的回調，可以處理來自各種組件的多個「消息」。

Answer 3

此代碼可用於使用您的GPSTracker類獲取位置，將您的代碼粘貼到您的活動onCreate方法上進行測試。是的，它會暫時阻止你的UI線程，但你會得到的位置。之後，您可以閱讀關於在Android中使用Service以獲得更好的想法。

  LocationResult locationResult = new LocationResult() { 
       @Override 
       public void gotLocation(Location location) { 
        Log.d("Activity","In gotLocation Listener"); 
        boolean hasAddedQr = false; 
        if(hasAddedQr){ 
         return; 
        } 
        hasAddedQr = true; 
        if (location != null) { 
         Log.d("Activity","Got the location"); 

         // Got the location! 
         try { 

          double lati = location.getLatitude(); 
          double longi = location.getLongitude(); 

          text.setText("Got Location: La="+lati+", Lo="+longi); 
         } catch (Exception e) { 
          // TODO: handle exception 
         } 
        } else { 
         GetLocation.this.runOnUiThread(new Runnable() { 

          @Override 
          public void run() { 
           // TODO Auto-generated method stub 
           text.setText("Location was returned null"); 

          } 
         }); 
        } 
       } 
      }; 
      GPSTracker myLocation = new GPSTracker(); 
      boolean isEnabled = myLocation.getLocation(GetLocation.this, locationResult); 
      if(!isEnabled){ 
       Log.d("Activity", "LOCATION SERVICES WERE NOT ENABLED"); 
       text.setText("Location service not available"); 
       getLocationBtn.setEnabled(true); 

      } 
      else{ 
       Log.d("Activity", "LOCATION SERVICES ENABLED"); 

      }