Question

http://blog.teamtreehouse.com/beginners-guide-location-android

我正在学习本教程，似乎在某个地方犯了错误。我不太确定我哪里出错了，我所知道的就是它说它是在我制作地图的部分引起的

public class MapsActivity extends FragmentActivity implements OnMapReadyCallback, GoogleApiClient.ConnectionCallbacks,
        GoogleApiClient.OnConnectionFailedListener, LocationListener {
private GoogleMap mMap;
private GoogleApiClient mGoogleApiClient;
private final static int CONNECTION_FAILURE_RESOLUTION_REQUEST = 9000;
private LocationRequest mLocationRequest;
public static final String TAG = MapsActivity.class.getSimpleName();


@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);

    mGoogleApiClient = new GoogleApiClient.Builder(this)
            .addConnectionCallbacks(this)
            .addOnConnectionFailedListener(this)
            .addApi(LocationServices.API)
            .build();

    // Create the LocationRequest object
    mLocationRequest = LocationRequest.create()
            .setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY)
            .setInterval(10 * 1000)        // 10 seconds, in milliseconds
            .setFastestInterval(1 * 1000); // 1 second, in milliseconds
}

@Override
protected void onResume() {
    super.onResume();
    setUpMap();
    mGoogleApiClient.connect();
}

@Override
protected void onPause() {
    super.onPause();
    if (mGoogleApiClient.isConnected()) {
        LocationServices.FusedLocationApi.removeLocationUpdates(mGoogleApiClient, this);
        mGoogleApiClient.disconnect();
    }
}


/**
 * 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));
}

@Override
public void onConnected(Bundle bundle) {
    Log.i(TAG, "Location services connected.");
    Location location = LocationServices.FusedLocationApi.getLastLocation(mGoogleApiClient);
    if (location == null) {
        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            // TODO: Consider calling
            //    ActivityCompat#requestPermissions
            // here to request the missing permissions, and then overriding
            //   public void onRequestPermissionsResult(int requestCode, String[] permissions,
            //                                          int[] grantResults)
            // to handle the case where the user grants the permission. See the documentation
            // for ActivityCompat#requestPermissions for more details.
            return;
        }
        LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient, mLocationRequest, this);
    }
    else {
        handleNewLocation(location);
    }
}

@Override
public void onConnectionSuspended(int i) {
    Log.i(TAG, "Location services suspended. Please reconnect.");
}

@Override
public void onConnectionFailed(ConnectionResult connectionResult) {
    if (connectionResult.hasResolution()) {
        try {
            // Start an Activity that tries to resolve the error
            connectionResult.startResolutionForResult(this, CONNECTION_FAILURE_RESOLUTION_REQUEST);
        } catch (IntentSender.SendIntentException e) {
            e.printStackTrace();
        }
    } else {
        Log.i(TAG, "Location services connection failed with code " + connectionResult.getErrorCode());
    }

}
private void handleNewLocation(Location location) {
    Log.d(TAG, location.toString());
    double currentLatitude = location.getLatitude();
    double currentLongitude = location.getLongitude();
    LatLng latLng = new LatLng(currentLatitude, currentLongitude);

    MarkerOptions options = new MarkerOptions()
            .position(latLng)
            .title("I am here!");

    mMap.addMarker(options);

    mMap.moveCamera(CameraUpdateFactory.newLatLng(latLng));
}

@Override
public void onLocationChanged(Location location) {
    handleNewLocation(location);
}

private void setUpMap() {
    mMap.addMarker(new MarkerOptions().position(new LatLng(0, 0)).title("Marker"));
}

}

根据控制台，它说它是setUpMap();方法onResume()行和setUpMap方法引起的。当我尝试运行应用程序时会发生什么错误导致它立即关闭。我也意识到我将它从setUpMapIfNeeded更改为SetUpMap，因为在教程中我没有找到任何setUpMapIfNeeded()方法。

Answer 1

你可以避免从setUpMap();调用onResume或者检查mMap是否为空

private void setUpMap() {
    if (mMap != null) {
        mMap.addMarker(new MarkerOptions().position(new LatLng(0, 0)).title("Marker"));
    }
}

顾名思义，getMapAsync以异步方式调用onMapReady，并且您无法保证在调用onMapReady之前已调用onResume < / p>

以下教程中的错误

1 个答案: