Question

这是我的项目，您在列表视图中单击医院名称，并在下一个活动中显示详细信息，详细信息下方是mapview。我的项目崩溃了，我从logcat

得到了这个错误

11-30 18:22:50.085: E/AndroidRuntime(13114): FATAL EXCEPTION: main
11-30 18:22:50.085: E/AndroidRuntime(13114): java.lang.NullPointerException
11-30 18:22:50.085: E/AndroidRuntime(13114):    at com.dr.droid.lee.HospResult$GeocoderTask.onPostExecute(HospResult.java:130)
11-30 18:22:50.085: E/AndroidRuntime(13114):    at com.dr.droid.lee.HospResult$GeocoderTask.onPostExecute(HospResult.java:1)
11-30 18:22:50.085: E/AndroidRuntime(13114):    at android.os.AsyncTask.finish(AsyncTask.java)
11-30 18:22:50.085: E/AndroidRuntime(13114):    at android.os.AsyncTask.access$600(AsyncTask.java)
11-30 18:22:50.085: E/AndroidRuntime(13114):    at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java)

这是我班级的代码

public class HospResult extends MapActivity {

    String hcity;
    String hregion;
    String hadd;
    String hname;
    String hcon;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        Typeface type = Typeface.createFromAsset(this.getAssets(),"MyriadPro-Bold.ttf");
        setContentView(R.layout.map);
        TextView hosname =  (TextView) findViewById(R.id.tvName);
        TextView hosreg =  (TextView) findViewById(R.id.tvRegion);
        TextView hosadd =  (TextView) findViewById(R.id.tvAddress);
        TextView hoscon =  (TextView) findViewById(R.id.tvContact);
        TextView hoscity =  (TextView) findViewById(R.id.tvCity);
        Bundle receive = getIntent().getExtras();
        hcity = receive.getString("city");
        hregion = receive.getString("region");
        hadd = receive.getString("address");
        hname = receive.getString("name");
        hcon = receive.getString("contact");
        hosname.setText(hname);
        hosreg.setText(hregion);
        hoscity.setText(hcity);
        hosadd.setText(hcon);
        hoscon.setText(hadd);
        hosname.setTypeface(type);
        hosreg.setTypeface(type);
        hosadd.setTypeface(type);
        hoscity.setTypeface(type);
        hoscon.setTypeface(type);
        //MapView mv =  (MapView) findViewById(R.id.mv1);
        //MapController mp = mv.getController();
        //mp.setZoom(15);
        String loc = hosname.getText().toString();
        //Toast.makeText(this, loc, Toast.LENGTH_SHORT).show();

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


    }

    @Override
    protected boolean isRouteDisplayed() {
        // TODO Auto-generated method stub
        return false;
    }

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

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

                try {
                    // Getting a maximum of 3 Address that matches the input text
                    addresses = geocoder.getFromLocationName(locationName[0], 1);
                } catch (IOException e) {
                    e.printStackTrace();
                }           
                return addresses;
            }


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

                // Getting Reference to MapView of the layout activity_main
                MapView mapView = (MapView) findViewById(R.id.mv1);

                // Setting ZoomControls
                mapView.setBuiltInZoomControls(true);

                // Getting MapController for the MapView
                MapController mc = mapView.getController();
                mc.setZoom(18);

                // Getting Drawable object corresponding to a resource image
                Drawable drawable = getResources().getDrawable(R.drawable.marker);


                // Getting Overlays of the map
                List<Overlay> overlays = mapView.getOverlays();

                // Creating an ItemizedOverlay
                LocationOverlay locationOverlay = new LocationOverlay(drawable,getBaseContext());

                // Clearing the overlays
                overlays.clear();

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

                    // Redraws the map to clear the overlays
                    mapView.invalidate();
                }

                // 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
                    GeoPoint p = new GeoPoint(
                                              (int)(address.getLatitude()*1E6),
                                              (int)(address.getLongitude()*1E6)
                                             );

                    String addressText = String.format("%s, %s",
                            address.getMaxAddressLineIndex() > 0 ? address.getAddressLine(0) : "",
                            address.getCountryName());


                    // Creating an OverlayItem to mark the point
                    OverlayItem overlayItem = new OverlayItem(p, "Location",addressText);

                    // Adding the OverlayItem in the LocationOverlay
                    locationOverlay.addOverlay(overlayItem);

                    // Adding locationOverlay to the overlay
                    overlays.add(locationOverlay);

                    // Locate the first location
                    if(i==0)
                        mc.animateTo(p);                    
                }

                // Redraws the map
                mapView.invalidate();

            }       
        }

}

第130行从这里开始

for(int i=0;i<addresses.size();i++){

在添加此类搜索功能之前，我的项目正在显示一个地图并运行罚款，但是在添加此搜索后，我从教程中获得的功能就崩溃了。想知道为什么我的项目在加载地图时崩溃了？我该怎么做才能解决这个问题？

Answer 1

尝试使用List<Address> addresses = new List<Address>();

初始化您的列表

正如@Carnal非常正确地说，如果您确定通过方法geocoder.getFromLocationName获得列表，那么您必须初始化您的列表然后您可以使用List<Address> addresses=null或者您可以检查列表的大小和根据您在内部使用它们进行循环使用。

Answer 2

您无需初始化List<Address> addresses = new List<Address>();，因为List<Address> addresses = null返回geocoder.getFromLocationName，您仍然可以List<Address>。在执行循环之前，您似乎没有检查地址列表是否为null。这似乎会破坏你的程序。

请检查：

if(addresses != null && addresses.size() > 0){
    for(int i=0;i<addresses.size();i++){
        // rest of your code..
    }
}

像Mapview一样搜索

2 个答案: