Question

以下代码来自Google地图活动，以查找用户输入的特定位置。它工作正常，但在没有持久的互联网连接时崩溃。请帮我修复此问题。 MainActivity.java类如下所示：

import android.location.Address;
import android.location.Geocoder;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.view.View;
import android.view.View.OnClickListener;
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.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 MainActivity
    extends FragmentActivity {

    GoogleMap googleMap;
    MarkerOptions markerOptions;
    LatLng latLng;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        SupportMapFragment supportMapFragment = (SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map);
        // Getting a reference to the map
        googleMap = supportMapFragment.getMap();
        // Getting reference to btn_find of the layout activity_main
        Button btn_find = (Button) findViewById(R.id.btn_find);
        // Defining button click event listener for the find button
        OnClickListener findClickListener = new OnClickListener() {

            @Override
            public void onClick(View v) {
                EditText etLocation = (EditText) findViewById(R.id.et_location);
                // Getting user input location
                String location = etLocation.getText().toString();
                if (location != null && !location.equals("")) {
                    new GeocoderTask().execute(location);
                }
            }
        };
        // Setting button click event listener for the find button
        btn_find.setOnClickListener(findClickListener);
    }

    // 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], 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();
            }
            // 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 = 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);
                googleMap.addMarker(markerOptions);
                // Locate the first location
                if (i == 0) {
                    googleMap.animateCamera(CameraUpdateFactory.newLatLng(latLng));
                }
            }
        }
    }
}

这是我的崩溃报告：

02-25 17:17:42.157 4312-4312/aravindaby.myapp123 E/test: Exception
02-25 17:17:42.157 4312-4312/aravindaby.myapp123 E/AndroidRuntime: FATAL EXCEPTION: main
java.lang.NullPointerException
at aravindaby.myapp123.MainActivity$GeocoderTask.onPostExecute(MainActivity.java:100)
at aravindaby.myapp123.MainActivity$GeocoderTask.onPostExecute(MainActivity.java:72)
at android.os.AsyncTask.finish(AsyncTask.java:631)
at android.os.AsyncTask.access$600(AsyncTask.java:177)
at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4793)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:808)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:575)
at dalvik.system.NativeStart.main(Native Method)

Answer 1

如果没有互联网连接，address为null。因此，在显示Toast消息后，您应该return控件。

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

应用程序在没有持久的Internet连接时崩溃

1 个答案: