獲取應用程序崩潰時檢索經度和緯度

Question

你好，我目前正在嘗試檢索我目前的經度和經度，並將它們轉換成地址，但我得到一個應用程序崩潰，每當我運行該程序。任何想法可能會造成這種情況？

活動：

public class LocatahActivity extends Activity { 

    LocationManager lm; 
    String towers; 

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

     lm = (LocationManager) getSystemService(Context.LOCATION_SERVICE); 
     Criteria criteria = new Criteria(); 
     criteria.setAccuracy(Criteria.ACCURACY_FINE); 
     criteria.setAltitudeRequired(false); 
     criteria.setBearingRequired(false); 
     criteria.setCostAllowed(true); 
     criteria.setPowerRequirement(Criteria.POWER_LOW); 

     towers = lm.getBestProvider(criteria, false); 
     Location location = lm.getLastKnownLocation(towers);   

     //double lat = (location.getLatitude()*1E6); 
     //double longi = (location.getLongitude()*1E6); 

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

     Log.e("TAG", "Latitude: " + lat); 
     Log.e("TAG", "Longitude: " + longi); 

     TextView myLatitude = (TextView)findViewById(R.id.mylatitude); 
     TextView myLongitude = (TextView)findViewById(R.id.mylongitude); 
     TextView myAddress = (TextView)findViewById(R.id.myaddress); 

     myLatitude.setText("Latitude: " + String.valueOf(lat)); 
     myLongitude.setText("Longitude: " + String.valueOf(longi)); 

     Geocoder geocoder = new Geocoder(this, Locale.ENGLISH); 

     try { 
      List<Address> addresses = geocoder.getFromLocation(lat, longi, 1); 
      StringBuilder sb = new StringBuilder(); 
      if (addresses.size() > 0) { 
      Address address = addresses.get(0); 
      for (int i = 0; i < address.getMaxAddressLineIndex(); i++) 
      sb.append(address.getAddressLine(i)).append("\n"); 
      sb.append(address.getLocality()).append("\n"); 
      sb.append(address.getPostalCode()).append("\n"); 
      sb.append(address.getCountryName()); 

      myAddress.setText(sb.toString()); 
      } 
     }catch (IOException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
      myAddress.setText("Cannont get Address!"); 
     } 

    } 


} 

清單：

<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" /> 
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" /> 
<uses-permission android:name="android.permission.INTERNET" /> 

logcat的

08-01 19:20:45.572: E/AndroidRuntime(6233): FATAL EXCEPTION: main 
08-01 19:20:45.572: E/AndroidRuntime(6233): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.location/com.example.location.LocatahActivity}: java.lang.NullPointerException 
08-01 19:20:45.572: E/AndroidRuntime(6233):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1967) 
08-01 19:20:45.572: E/AndroidRuntime(6233):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1992) 
08-01 19:20:45.572: E/AndroidRuntime(6233):  at android.app.ActivityThread.access$600(ActivityThread.java:127) 
08-01 19:20:45.572: E/AndroidRuntime(6233):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1158) 
08-01 19:20:45.572: E/AndroidRuntime(6233):  at android.os.Handler.dispatchMessage(Handler.java:99) 
08-01 19:20:45.572: E/AndroidRuntime(6233):  at android.os.Looper.loop(Looper.java:137) 
08-01 19:20:45.572: E/AndroidRuntime(6233):  at android.app.ActivityThread.main(ActivityThread.java:4511) 
08-01 19:20:45.572: E/AndroidRuntime(6233):  at java.lang.reflect.Method.invokeNative(Native Method) 
08-01 19:20:45.572: E/AndroidRuntime(6233):  at java.lang.reflect.Method.invoke(Method.java:511) 
08-01 19:20:45.572: E/AndroidRuntime(6233):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:980) 
08-01 19:20:45.572: E/AndroidRuntime(6233):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:747) 
08-01 19:20:45.572: E/AndroidRuntime(6233):  at dalvik.system.NativeStart.main(Native Method) 
08-01 19:20:45.572: E/AndroidRuntime(6233): Caused by: java.lang.NullPointerException 
08-01 19:20:45.572: E/AndroidRuntime(6233):  at com.example.location.LocatahActivity.onCreate(LocatahActivity.java:44) 
08-01 19:20:45.572: E/AndroidRuntime(6233):  at android.app.Activity.performCreate(Activity.java:4470) 
08-01 19:20:45.572: E/AndroidRuntime(6233):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1052) 
08-01 19:20:45.572: E/AndroidRuntime(6233):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1931) 
08-01 19:20:45.572: E/AndroidRuntime(6233):  ... 11 more 

Answer 1

好像你location對象爲null。這可能是因爲您正在使用getLastKnownLocation()。如果沒有最後一個位置，或者提供程序當前被禁用，您將使用此方法得到一個空值。

除此之外，你說你想要當前位置。這是獲取當前位置的錯誤方法。要獲取用戶的當前位置，您需要使用LocationManager API中給出的requestLocationUpdates（）方法。使用這些和一個LocationListener接收更新。請記住，在獲得位置之前，它可能需要幾秒到幾分鐘的時間。