Android GPS基础

package org.example.locationtest;
import java.util.List;
import android.app.Activity;
import android.location.Criteria;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.location.LocationProvider;
import android.os.Bundle;
import android.widget.TextView;

public class LocationTest extends Activity implements
      LocationListener { 
   // Define human readable names
   private static final String[] A = { "invalid", "n/a", "fine", "coarse" };
   private static final String[] P = { "invalid", "n/a", "low", "medium",
         "high" };
   private static final String[] S = { "out of service", "temporarily unavailable", "available" };
   
   private LocationManager mgr;
   private TextView output;
   private String best;

   @Override
   public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.main);
      mgr = (LocationManager) getSystemService(LOCATION_SERVICE); 
      output = (TextView) findViewById(R.id.output);

      log("Location providers:");
      dumpProviders(); 

      Criteria criteria = new Criteria(); 
      best = mgr.getBestProvider(criteria, true);//获取最好的提供者
      log("\nBest provider is: " + best);

//      注：这里取到的GPS值是目前存储在GPS上的Location值，
//      如果刚刚打开GPS就用这个方法取Location取到的会是上一次代开GPS时取到的旧值。
//      等待GPS取得新值需要用LocationListener里的 onLocationChanged。
      log("\nLocations (starting with last known):");
      Location location = mgr.getLastKnownLocation(best); //通过最好的提供者获得GPS的方法
      dumpLocation(location);
   }
   
   @Override
   protected void onResume() {
      super.onResume();
      // Start updates (doc recommends delay >= 60000 ms)
      mgr.requestLocationUpdates(best, 15000, 1, this);//通过best启动（例如设置成LocationManager.GPS_PROVIDER就是通过gps启动），Location更新的设置是每隔15000ms更新一次，最后一个参数是LocationListener的一个引用，这个类需要实现
   }

   @Override
   protected void onPause() {
      super.onPause();
//      停止GPS运行：
      mgr.removeUpdates(this);
   }
   //如果需要去到GPS启动后取到的Location,必须用这个！  
   public void onLocationChanged(Location location) {
      dumpLocation(location);
   }
   // Provider被disable时触发此函数，比如GPS被关闭   
   public void onProviderDisabled(String provider) {
      log("\nProvider disabled: " + provider);
   }
   //  Provider被enable时触发此函数，比如GPS被打开   
   public void onProviderEnabled(String provider) {
      log("\nProvider enabled: " + provider);
   }
   // Provider的转态在可用、暂时不可用和无服务三个状态直接切换时触发此函数   
   public void onStatusChanged(String provider, int status,
         Bundle extras) {
      log("\nProvider status changed: " + provider + ", status="
            + S[status] + ", extras=" + extras);
   }

   /** Write a string to the output window */
   private void log(String string) {
      output.append(string + "\n");
   }

   /** Write information from all location providers */
   private void dumpProviders() {
      List<String> providers = mgr.getAllProviders();
      for (String provider : providers) {
         dumpProvider(provider);
      }
   }

   /** Write information from a single location provider */
   private void dumpProvider(String provider) {
      LocationProvider info = mgr.getProvider(provider);
      StringBuilder builder = new StringBuilder();
      builder.append("LocationProvider[")
            .append("name=")
            .append(info.getName())
            .append(",enabled=")
            .append(mgr.isProviderEnabled(provider))//检测GPS是否已经启动:
            .append(",getAccuracy=")
            .append(A[info.getAccuracy() + 1])
            .append(",getPowerRequirement=")
            .append(P[info.getPowerRequirement() + 1])
            .append(",hasMonetaryCost=")
            .append(info.hasMonetaryCost())
            .append(",requiresCell=")
            .append(info.requiresCell())
            .append(",requiresNetwork=")
            .append(info.requiresNetwork())
            .append(",requiresSatellite=")
            .append(info.requiresSatellite())
            .append(",supportsAltitude=")
            .append(info.supportsAltitude())
            .append(",supportsBearing=")
            .append(info.supportsBearing())
            .append(",supportsSpeed=")
            .append(info.supportsSpeed())
            .append("]");
      log(builder.toString());
   }

   /** Describe the given location, which might be null */
   private void dumpLocation(Location location) {
      if (location == null)
         log("\nLocation[unknown]");
      else
//    	  double latitude = location.getLatitude();     //经度   
//        double longitude = location.getLongitude(); //纬度   
//        double altitude =  location.getAltitude();     //海拔   
         log("\n" + location.toString());
   }

}