我在按下按鈕（在搜索按鈕上）時得到NullpointerException java.lang.NullPointerException

Question

在etSearch（EDitText）中寫入地址後，當我單擊按鈕「btnSearch」時，它應該顯示地圖中的地址.But它給了我errors.Can幫我

錯誤是

02-07 19:34:30.251: E/AndroidRuntime(24364): FATAL EXCEPTION: main 
02-07 19:34:30.251: E/AndroidRuntime(24364): java.lang.NullPointerException 
02-07 19:34:30.251: E/AndroidRuntime(24364): at com.mamun.tasktest.MapActivity$GeocoderTask.onPostExecute(MapActivity.java:178) 
02-07 19:34:30.251: E/AndroidRuntime(24364): at com.mamun.tasktest.MapActivity$GeocoderTask.onPostExecute(MapActivity.java:1) 
02-07 19:34:30.251: E/AndroidRuntime(24364): at android.os.AsyncTask.finish(AsyncTask.java:631) 
02-07 19:34:30.251: E/AndroidRuntime(24364): at android.os.AsyncTask.access$600(AsyncTask.java:177) 
02-07 19:34:30.251: E/AndroidRuntime(24364): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644) 
02-07 19:34:30.251: E/AndroidRuntime(24364): at android.os.Handler.dispatchMessage(Handler.java:99) 
02-07 19:34:30.251: E/AndroidRuntime(24364): at android.os.Looper.loop(Looper.java:137) 
02-07 19:34:30.251: E/AndroidRuntime(24364): at android.app.ActivityThread.main(ActivityThread.java:4960) 
02-07 19:34:30.251: E/AndroidRuntime(24364): at java.lang.reflect.Method.invokeNative(Native Method) 
02-07 19:34:30.251: E/AndroidRuntime(24364): at java.lang.reflect.Method.invoke(Method.java:511) 
02-07 19:34:30.251: E/AndroidRuntime(24364): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1038) 
02-07 19:34:30.251: E/AndroidRuntime(24364): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:805) 
02-07 19:34:30.251: E/AndroidRuntime(24364): at dalvik.system.NativeStart.main(Native Method) 


public class MapActivity extends Activity implements 
     GooglePlayServicesClient.ConnectionCallbacks, 
     GooglePlayServicesClient.OnConnectionFailedListener, LocationListener { 

    private LocationManager manager; 

    private TextView tvAddress; 
    private Button btnSearch; 
    private EditText etSearch; 
    private LocationClient locationClient; 
    private GoogleMap googleMap; 
    private MapFragment mapFragment; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 

     super.onCreate(savedInstanceState); 

     setContentView(R.layout.map); 

     manager = (LocationManager) getSystemService(LOCATION_SERVICE); 

     tvAddress = (TextView) findViewById(R.id.tvaddress); 
     btnSearch = (Button) findViewById(R.id.btnSearch); 
     etSearch= (EditText)findViewById(R.id.etSearch); 
     mapFragment = (MapFragment) getFragmentManager().findFragmentById(
       R.id.maps); 
     googleMap = mapFragment.getMap(); 
     locationClient = new LocationClient(this, this, this); 

    } 

    public void onSearch(View v) { 

      // Getting user input location 
      String location = etSearch.getText().toString(); 

      if(location!=null && !location.equals("")){ 
       new GeocoderTask().execute(location); 
      } 
    } 

    @Override 
    protected void onResume() { 
     // TODO Auto-generated method stub 
     super.onResume(); 
     locationClient.connect(); 
    } 

    @Override 
    protected void onPause() { 
     // TODO Auto-generated method stub 
     super.onPause(); 
     locationClient.disconnect(); 
    } 

    @Override 
    public void onLocationChanged(Location location) { 
     // TODO Auto-generated method stub 

    } 

    @Override 
    public void onConnectionFailed(ConnectionResult result) { 

    } 

    @Override 
    public void onConnected(Bundle connectionHint) { 
     Location currentLocation = locationClient.getLastLocation(); 
     double lat = currentLocation.getLatitude(); 
     double lng = currentLocation.getLongitude(); 
     // txtLocation.setText(lat + ", " + lng); 

     Geocoder geocoder = new Geocoder(this); 
     try { 
      ArrayList<Address> address = (ArrayList<Address>) geocoder 
        .getFromLocation(currentLocation.getLatitude(), 
          currentLocation.getLongitude(), 5); 
      Address addr = address.get(0); 
      String currentAddress = (addr.getAddressLine(0) + "-" 
        + addr.getAdminArea() + "-" + addr.getLocality() + "-" 
        + addr.getPostalCode() + "-" + addr.getCountryCode()); 
      MarkerOptions options = new MarkerOptions(); 
      options.position(new LatLng(lat, lng)); 
      options.title(currentAddress); 
      options.snippet("Current location"); 
      options.icon(BitmapDescriptorFactory 
        .defaultMarker(BitmapDescriptorFactory.HUE_AZURE)); 
      if (googleMap != null) { 
       googleMap.moveCamera(CameraUpdateFactory.newLatLngZoom(
         new LatLng(lat, lng), 14.0f)); 
       googleMap.addMarker(options); 
      } else { 
       Toast.makeText(getApplicationContext(), "Map is null", 
         Toast.LENGTH_LONG).show(); 
      } 

     } catch (IOException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
     } 
    } 

    @Override 
    public void onDisconnected() { 
     // TODO Auto-generated method stub 

    } 

    // An AsyncTask class for accessing the GeoCoding Web Service 
    private class GeocoderTask extends AsyncTask<String, Void, ArrayList<Address>>{ 

     @Override 
     protected ArrayList<Address> doInBackground(String... locationName) { 
      // Creating an instance of Geocoder class 
      Geocoder geocoder = new Geocoder(getBaseContext()); 
      ArrayList<Address> addresses = null; 

      try { 
       // Getting a maximum of 3 Address that matches the input text 
       addresses = (ArrayList<Address>) geocoder.getFromLocationName(locationName[0], 3); 
      } catch (IOException e) { 
       e.printStackTrace(); 
      } 
      return addresses; 
     } 

     @Override 
     protected void onPostExecute(ArrayList<Address> addresses) { 

      if(addresses==null || addresses.size()==0){ 
       Toast.makeText(getBaseContext(), "No Location found", Toast.LENGTH_SHORT).show(); 
      } 

      // Clears all the existing markers on the map 
      // googleMap.clear(); 

      // Adding Markers on Google Map for each matching address 
      for(int i=0;i<addresses.size();i++){ 

       Address address = (Address) addresses.get(i); 

       // Creating an instance of GeoPoint, to display in Google Map 
       LatLng latLng ; 
     latLng = new LatLng(address.getLatitude(), address.getLongitude()); 

       String addressText = String.format("%s, %s", 
       address.getMaxAddressLineIndex() > 0 ? address.getAddressLine(0) : "", 
       address.getCountryName()); 
       MarkerOptions markerOptions = new MarkerOptions(); 
       // markerOptions = new MarkerOptions(); 
       markerOptions.position(latLng); 
       markerOptions.title(addressText); 

       googleMap.addMarker(markerOptions); 

       // Locate the first location 
       if(i==0) 
        googleMap.animateCamera(CameraUpdateFactory.newLatLng(latLng)); 
      } 
     } 
    } 
} 

Answer 1

你必須退出功能時，地址爲空。

@Override 
protected void onPostExecute(ArrayList<Address> addresses) { 
    if(addresses==null || addresses.size()==0){ 
     Toast.makeText(getBaseContext(), "No Location found", Toast.LENGTH_SHORT).show(); 
     return; 
    }