java - 在 Android 应用程序中进行地理编码

Question

我无法弄清楚为什么我每次运行该应用程序时都会收到空指针异常。这个 android 应用程序找到了这个地方并使用地理编码在 map 上标记了它。但是我没有成功这样做并且没有得到知道错误在哪里。请帮助!主要 Activity 代码如下:

package com.dutt.rishabh.locator;

import android.location.Address;
import android.location.Geocoder;
import android.os.AsyncTask;
import android.support.v4.app.FragmentActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;


import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.OnMapReadyCallback;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;

import java.io.IOException;
import java.util.List;

public class MapsActivity extends FragmentActivity implements OnMapReadyCallback {

    private GoogleMap mMap;
    EditText x;
    Button bfind;
    String location;
    MarkerOptions markerOptions;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_maps);
        // Obtain the SupportMapFragment and get notified when the map is ready to be used.
        SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
                .findFragmentById(R.id.map);
        mapFragment.getMapAsync(this);

        bfind=(Button)findViewById(R.id.bfind);
        View.OnClickListener findClickListener =new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                x=(EditText)findViewById(R.id.etsearch);
                location=x.getText().toString();
                if(location!=null || location.equals("")){
                    new GeocoderTask().execute(location);
                }
            }
        };
        bfind.setOnClickListener(findClickListener);



    }
    private class GeocoderTask extends AsyncTask<String, Void, List<Address>>{
        @Override
        protected List<Address> doInBackground(String... strings) {
            Geocoder geocoder = new Geocoder(getBaseContext());
            List<Address> addresses=null;
            try {
                addresses=geocoder.getFromLocationName(strings[0],3);
            } catch (IOException e) {
                e.printStackTrace();
            }
            return addresses;
        }
        @Override
        protected void onPostExecute(List<Address> addresses){
            if(addresses==null || addresses.size()==0){
                Toast.makeText(getBaseContext(),"No location found",Toast.LENGTH_SHORT).show();
            }
            mMap.clear();
            for(int i=0;i<addresses.size();i++){
                Address address= addresses.get(i);
                LatLng latLng=new LatLng(address.getLatitude(),address.getLongitude());
                String addressText=String.format("%s,%s",address.getMaxAddressLineIndex()>0?address.getAddressLine(0):"",address.getCountryName());
                markerOptions=new MarkerOptions();
                markerOptions.position(latLng);
                markerOptions.title(addressText);

                mMap.addMarker(markerOptions);
                if(i==0){
                    mMap.animateCamera(CameraUpdateFactory.newLatLng(latLng));
                }
            }
        }
    }



    /**
     * Manipulates the map once available.
     * This callback is triggered when the map is ready to be used.
     * This is where we can add markers or lines, add listeners or move the camera. In this case,
     * we just add a marker near Sydney, Australia.
     * If Google Play services is not installed on the device, the user will be prompted to install
     * it inside the SupportMapFragment. This method will only be triggered once the user has
     * installed Google Play services and returned to the app.
     */
    @Override
    public void onMapReady(GoogleMap googleMap) {
        mMap = googleMap;

        // Add a marker in Sydney and move the camera
        LatLng sydney = new LatLng(-34, 151);
        mMap.addMarker(new MarkerOptions().position(sydney).title("Marker in Sydney"));
        mMap.moveCamera(CameraUpdateFactory.newLatLng(sydney));
    }
}

请帮助并请指出我的错误，以便我理解。以下是 logcat:

07-26 15:02:02.264 30388-30388/com.dutt.rishabh.locator E/AndroidRuntime: FATAL EXCEPTION: main
                                                                          Process: com.dutt.rishabh.locator, PID: 30388
                                                                          java.lang.NullPointerException
                                                                              at com.dutt.rishabh.locator.MapsActivity$GeocoderTask.onPostExecute(MapsActivity.java:75)
                                                                              at com.dutt.rishabh.locator.MapsActivity$GeocoderTask.onPostExecute(MapsActivity.java:57)
                                                                              at android.os.AsyncTask.finish(AsyncTask.java:632)
                                                                              at android.os.AsyncTask.access$600(AsyncTask.java:177)
                                                                              at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:645)
                                                                              at android.os.Handler.dispatchMessage(Handler.java:110)
                                                                              at android.os.Looper.loop(Looper.java:193)
                                                                              at android.app.ActivityThread.main(ActivityThread.java:5345)
                                                                              at java.lang.reflect.Method.invokeNative(Native Method)
                                                                              at java.lang.reflect.Method.invoke(Method.java:515)
                                                                              at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:828)
                                                                              at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:644)
                                                                              at dalvik.system.NativeStart.main(Native Method)

Answer 1

地址空检查

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

或添加回车

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