這是我的代碼始終返回“無位置”的原因嗎？

Question

我正在制作一個需要用戶位置的應用程序。 到目前為止，這是其代碼：

import android.Manifest;
import android.app.Activity;
import android.content.Context;
import android.content.pm.PackageManager;
import android.location.Criteria;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Build;
import android.os.Bundle;
import android.util.Log;
import android.view.View;

public class MainActivity extends Activity implements LocationListener {

LocationManager locationManager;
String provider;
Location location;


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

    locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);

    provider = LocationManager.NETWORK_PROVIDER;


    location = locationManager.getLastKnownLocation(provider);


}

public void locationStuff(View view) {
    if (location != null) {

        Log.i("Location Info", "Location achieved!");

    } else {

        Log.i("Location Info", "No location :(");

    }

}


@Override
protected void onResume() {
    super.onResume();


    locationManager.requestLocationUpdates(provider, 400, 1, this);

}


@Override
protected void onPause() {
    super.onPause();


    locationManager.removeUpdates(this);

}

@Override
public void onLocationChanged(Location location) {

    Double lat = location.getLatitude();
    Double lng = location.getLongitude();

    Log.i("Location info: Lat", lat.toString());
    Log.i("Location info: Lng", lng.toString());

}

@Override
public void onStatusChanged(String provider, int status, Bundle extras) {

}

@Override
public void onProviderEnabled(String provider) {

}

@Override
public void onProviderDisabled(String provider) {

}


public void getLocation(View view) {

    Location location = locationManager.getLastKnownLocation(provider);

    onLocationChanged(location);


}

}

它僅返回“無位置”。 我試圖讓它輸出“實現的位置”。 我在錯誤圖片上附加了一個鏈接。 如果您發現問題所在，請告訴我。 錯誤圖片

Answer 1

您可以使用GoggleLocationClient獲得更好的結果。

public class MainActivity extends AppCompatActivity  implements GoogleApiClient.ConnectionCallbacks,GoogleApiClient.OnConnectionFailedListener, LocationListener {

GoogleApiClient mGoogleApiClient;
Location mLastLocation;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    createLocationRequest();
    TextView mTextView = (TextView)findViewById(R.id.mTextView);
    mTextView.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            buildGoogleApipClient();
            mGoogleApiClient.connect();


        }
    });

}
LocationRequest mLocationRequest;
protected void createLocationRequest() {
    mLocationRequest = new LocationRequest();
    mLocationRequest.setInterval(10000);
    mLocationRequest.setFastestInterval(5000);
    mLocationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
}

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

}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_main, menu);
    return true;
}

@Override
protected void onResume() {
    super.onResume();
    Toast.makeText(this, "Yes calling", Toast.LENGTH_LONG).show();
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}

@Override
public void onConnected(Bundle bundle) {
    mLastLocation = LocationServices.FusedLocationApi.getLastLocation(mGoogleApiClient);
    if(mLastLocation!=null){
        Toast.makeText(this,mLastLocation.getLatitude()+"-----"+mLastLocation.getLongitude(),Toast.LENGTH_LONG).show();
    }
    if (true) {
        startLocationUpdates();
    }


}
protected void startLocationUpdates() {
    /*LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient, mLocationRequest, this);*/
    LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient, mLocationRequest, this);

}

@Override
public void onConnectionSuspended(int i) {

}

@Override
public void onConnectionFailed(ConnectionResult connectionResult) {

}

@Override
public void onLocationChanged(Location location) {
    location = location;
    //mLastUpdateTime = DateFormat.getTimeInstance().format(new Date());
    updateUI();
}

private void updateUI() {
    Toast.makeText(this,mLastLocation.getLatitude()+"-----"+mLastLocation.getLongitude(),Toast.LENGTH_LONG).show();
}
  }

Answer 2

從我所看到的，您沒有檢查是否已將設備設置為啟用查找位置，也沒有檢查任何可能的空值。 我添加了一些使用GPS且沒有網絡連接的代碼。

public Location getLocation() {
    try {
        locationManager = (LocationManager) mContext
                .getSystemService(LOCATION_SERVICE);
        // getting GPS status
        isGPSEnabled = locationManager
                .isProviderEnabled(LocationManager.GPS_PROVIDER);
        // getting network status
        isNetworkEnabled = locationManager
                .isProviderEnabled(LocationManager.NETWORK_PROVIDER);
        if (!isGPSEnabled && !isNetworkEnabled) {
            // no network provider is enabled
        } else {
            this.canGetLocation = true;
            // First get destination from Network Provider
            if (isNetworkEnabled) {
                locationManager.requestLocationUpdates(
                        LocationManager.NETWORK_PROVIDER,
                        MIN_TIME_BW_UPDATES,
                        MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
                //  Log.d("Network", "Network");
                if (locationManager != null) {
                    location = locationManager.getLastKnownLocation(
                            LocationManager.NETWORK_PROVIDER);
                    if (location != null) {
                        latitude = location.getLatitude();
                        longitude = location.getLongitude();
                    }
                }
            }
            // if GPS Enabled get lat/long using GPS Services
            if (isGPSEnabled) {
                if (location == null) {
                    locationManager.requestLocationUpdates(
                            LocationManager.GPS_PROVIDER,
                            MIN_TIME_BW_UPDATES,
                            MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
                    // Log.d("GPS Enabled", "GPS Enabled");
                    if (locationManager != null) {
                        location = locationManager.getLastKnownLocation(
                                LocationManager.GPS_PROVIDER);
                        if (location != null) {
                            latitude = location.getLatitude();
                            longitude = location.getLongitude();
                        }
                    }
                }
            }
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
    return location;
}

然后使用GPS和網絡可用性檢查，可以控制程序流程，以提示用戶啟用這些設置或控制空指針。