匿名类不是抽象的，不会覆盖（Android + Retrofit）

Question

我正在尝试使用 this tutorial 之后的改造来让 Google 地图显示附近的地方。

我收到此错误：

错误：(158, 46) 错误：不是抽象的，也不是 覆盖抽象方法 onFailure(Call,Throwable) 回调

Error:(159, 13) 错误：方法没有覆盖或实现方法 来自超类型

我尝试使用 alt + enter 来实现方法，但它与教程有所不同，并且会弄乱代码。

这是我的主要内容（与教程相同）

MapsActivity.java

package example.googlemapsapp;

import android.Manifest;
import android.content.pm.PackageManager;
import android.location.Location;
import android.os.Build;
import android.support.v4.app.ActivityCompat;
import android.support.v4.app.FragmentActivity;
import android.os.Bundle;
import android.support.v4.content.ContextCompat;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;


import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.GoogleApiAvailability;
import com.google.android.gms.common.api.GoogleApiClient;
import com.google.android.gms.location.LocationListener;
import com.google.android.gms.location.LocationRequest;
import com.google.android.gms.location.LocationServices;
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.BitmapDescriptorFactory;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.Marker;
import com.google.android.gms.maps.model.MarkerOptions;

import java.util.HashMap;

import example.googlemapsapp.POJO.Example;
import retrofit2.Call;
import retrofit2.Callback;
import retrofit2.Response;
import retrofit2.Retrofit;
import retrofit2.converter.gson.GsonConverterFactory;


public class MapsActivity extends FragmentActivity implements OnMapReadyCallback,
        GoogleApiClient.ConnectionCallbacks,
        GoogleApiClient.OnConnectionFailedListener,
        LocationListener {

    private GoogleMap mMap;
    double latitude;
    double longitude;
    private int PROXIMITY_RADIUS = 10000;
    GoogleApiClient mGoogleApiClient;
    Location mLastLocation;
    Marker mCurrLocationMarker;
    LocationRequest mLocationRequest;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_maps);

        if (android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            checkLocationPermission();
        }

        //show error dialog if Google Play Services not available
        if (!isGooglePlayServicesAvailable()) {
            Log.d("onCreate", "Google Play Services not available. Ending Test case.");
            finish();
        }
        else {
            Log.d("onCreate", "Google Play Services available. Continuing.");
        }

        // 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);
    }

    private boolean isGooglePlayServicesAvailable() {
        GoogleApiAvailability googleAPI = GoogleApiAvailability.getInstance();
        int result = googleAPI.isGooglePlayServicesAvailable(this);
        if(result != ConnectionResult.SUCCESS) {
            if(googleAPI.isUserResolvableError(result)) {
                googleAPI.getErrorDialog(this, result,
                        0).show();
            }
            return false;
        }
        return true;
    }

    /**
     * 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;
        mMap.setMapType(GoogleMap.MAP_TYPE_HYBRID);

        //Initialize Google Play Services
        if (android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            if (ContextCompat.checkSelfPermission(this,
                    Manifest.permission.ACCESS_FINE_LOCATION)
                    == PackageManager.PERMISSION_GRANTED) {
                buildGoogleApiClient();
                mMap.setMyLocationEnabled(true);
            }
        } else {
            buildGoogleApiClient();
            mMap.setMyLocationEnabled(true);
        }

        Button btnRestaurant = (Button) findViewById(R.id.btnRestaurant);
        btnRestaurant.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                build_retrofit_and_get_response("restaurant");
            }
        });

        Button btnHospital = (Button) findViewById(R.id.btnHospital);
        btnHospital.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                build_retrofit_and_get_response("hospital");
            }
        });

        Button btnSchool = (Button) findViewById(R.id.btnSchool);
        btnSchool.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                build_retrofit_and_get_response("school");
            }
        });
    }

    private void build_retrofit_and_get_response(String type) {

        String url = "https://maps.googleapis.com/maps/";

        Retrofit retrofit = new Retrofit.Builder()
                .baseUrl(url)
                .addConverterFactory(GsonConverterFactory.create())
                .build();

        RetrofitMaps service = retrofit.create(RetrofitMaps.class);

        Call<Example> call = service.getNearbyPlaces(type, latitude + "," + longitude, PROXIMITY_RADIUS);

        call.enqueue(new Callback<Example>() {

            @Override
            public void onResponse(Response<Example> response, Retrofit retrofit) {

                try {
                    mMap.clear();
                    // This loop will go through all the results and add marker on each location.
                    for (int i = 0; i < response.body().getResults().size(); i++) {
                        Double lat = response.body().getResults().get(i).getGeometry().getLocation().getLat();
                        Double lng = response.body().getResults().get(i).getGeometry().getLocation().getLng();
                        String placeName = response.body().getResults().get(i).getName();
                        String vicinity = response.body().getResults().get(i).getVicinity();
                        MarkerOptions markerOptions = new MarkerOptions();
                        LatLng latLng = new LatLng(lat, lng);
                        // Position of Marker on Map
                        markerOptions.position(latLng);
                        // Adding Title to the Marker
                        markerOptions.title(placeName + " : " + vicinity);
                        // Adding Marker to the Camera.
                        Marker m = mMap.addMarker(markerOptions);
                        // Adding colour to the marker
                        markerOptions.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_RED));
                        // move map camera
                        mMap.moveCamera(CameraUpdateFactory.newLatLng(latLng));
                        mMap.animateCamera(CameraUpdateFactory.zoomTo(11));
                    }
                } catch (Exception e) {
                    Log.d("onResponse", "There is an error");
                    e.printStackTrace();
                }
            }
            @Override
            public void onFailure(Throwable t) {
                Log.d("onFailure", t.toString());
            }
        });

    }

    protected synchronized void buildGoogleApiClient() {
        mGoogleApiClient = new GoogleApiClient.Builder(this)
                .addConnectionCallbacks(this)
                .addOnConnectionFailedListener(this)
                .addApi(LocationServices.API)
                .build();
        mGoogleApiClient.connect();
    }

    @Override
    public void onConnected(Bundle bundle) {
        mLocationRequest = new LocationRequest();
        mLocationRequest.setInterval(1000);
        mLocationRequest.setFastestInterval(1000);
        mLocationRequest.setPriority(LocationRequest.PRIORITY_BALANCED_POWER_ACCURACY);
        if (ContextCompat.checkSelfPermission(this,
                Manifest.permission.ACCESS_FINE_LOCATION)
                == PackageManager.PERMISSION_GRANTED) {
            LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient, mLocationRequest, this);
        }
    }

    @Override
    public void onConnectionSuspended(int i) {

    }

    @Override
    public void onLocationChanged(Location location) {

        Log.d("onLocationChanged", "entered");

        mLastLocation = location;
        if (mCurrLocationMarker != null) {
            mCurrLocationMarker.remove();
        }
        //Place current location marker
        latitude = location.getLatitude();
        longitude = location.getLongitude();
        LatLng latLng = new LatLng(location.getLatitude(), location.getLongitude());
        MarkerOptions markerOptions = new MarkerOptions();
        markerOptions.position(latLng);
        markerOptions.title("Current Position");

        // Adding colour to the marker
        markerOptions.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_MAGENTA));

        // Adding Marker to the Map
        mCurrLocationMarker = mMap.addMarker(markerOptions);

        //move map camera
        mMap.moveCamera(CameraUpdateFactory.newLatLng(latLng));
        mMap.animateCamera(CameraUpdateFactory.zoomTo(11));

        Log.d("onLocationChanged", String.format("latitude:%.3f longitude:%.3f", latitude, longitude));

        Log.d("onLocationChanged", "Exit");
    }

    @Override
    public void onConnectionFailed(ConnectionResult connectionResult) {

    }

    public static final int MY_PERMISSIONS_REQUEST_LOCATION = 99;
    public boolean checkLocationPermission(){
        if (ContextCompat.checkSelfPermission(this,
                Manifest.permission.ACCESS_FINE_LOCATION)
                != PackageManager.PERMISSION_GRANTED) {

            // Asking user if explanation is needed
            if (ActivityCompat.shouldShowRequestPermissionRationale(this,
                    Manifest.permission.ACCESS_FINE_LOCATION)) {

                // Show an explanation to the user *asynchronously* -- don't block
                // this thread waiting for the user's response! After the user
                // sees the explanation, try again to request the permission.

                //Prompt the user once explanation has been shown
                ActivityCompat.requestPermissions(this,
                        new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
                        MY_PERMISSIONS_REQUEST_LOCATION);


            } else {
                // No explanation needed, we can request the permission.
                ActivityCompat.requestPermissions(this,
                        new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
                        MY_PERMISSIONS_REQUEST_LOCATION);
            }
            return false;
        } else {
            return true;
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode,
                                           String permissions[], int[] grantResults) {
        switch (requestCode) {
            case MY_PERMISSIONS_REQUEST_LOCATION: {
                // If request is cancelled, the result arrays are empty.
                if (grantResults.length > 0
                        && grantResults[0] == PackageManager.PERMISSION_GRANTED) {

                    // permission was granted. Do the
                    // contacts-related task you need to do.
                    if (ContextCompat.checkSelfPermission(this,
                            Manifest.permission.ACCESS_FINE_LOCATION)
                            == PackageManager.PERMISSION_GRANTED) {

                        if (mGoogleApiClient == null) {
                            buildGoogleApiClient();
                        }
                        mMap.setMyLocationEnabled(true);
                    }

                } else {

                    // Permission denied, Disable the functionality that depends on this permission.
                    Toast.makeText(this, "permission denied", Toast.LENGTH_LONG).show();
                }
                return;
            }

            // other 'case' lines to check for other permissions this app might request.
            // You can add here other case statements according to your requirement.
        }
    }
}

Answer 1

The signature of onResponse 与你所拥有的不同。

你有：

public void onResponse( Response<Example> response, Retrofit retrofit)

应该是：

public void onResponse(Call<Example> call, Response<Example> response)

你的onFailure也需要带一个Call参数：

public void onFailure(Call<Example> call, Throwable t)

Retrofit 版本之间的方法签名可能已更改，并且本教程使用的版本可能比您的版本旧。但我只是推测。

Answer 2

诊断非常容易：只需阅读错误消息并理解即可：

它表示您正在尝试子类化CallBack 接口，因此您必须覆盖它声明的所有方法。但你不是；因为你还没有重写onFailure(Call<T> call, Throwable t) 方法。

看到了吗？您错过了在onFailure 方法中添加call 参数。

不要太相信教程；用它作为基础，而不是作为福音。也许该教程基于 Retrofit 的早期版本。 （或者它可能包含错误）。