如何在后台执行应用程序？

Question

两周前我开始使用Android Studio了，而且我每天都在学习，但是，我今天想要你的帮助代码，可能对你来说非常简单。

package com.exampledemo.parsaniahardik.gpsdemocode;

import android.Manifest;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.location.Location;
import android.location.LocationManager;
import android.provider.Settings;
import android.support.v4.app.ActivityCompat;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.widget.TextView;
import android.widget.Toast;


import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.api.GoogleApiClient;
import com.google.android.gms.location.LocationRequest;
import com.google.android.gms.location.LocationServices;
import com.google.android.gms.maps.model.LatLng;

public class MainActivity extends AppCompatActivity implements     GoogleApiClient.ConnectionCallbacks, GoogleApiClient.OnConnectionFailedListener, com.google.android.gms.location.LocationListener {

private static final String TAG = "MainActivity";
private TextView mLatitudeTextView;
private TextView mLongitudeTextView;
private GoogleApiClient mGoogleApiClient;
private Location mLocation;
private LocationManager mLocationManager;

private LocationRequest mLocationRequest;
private com.google.android.gms.location.LocationListener listener;
private long UPDATE_INTERVAL = 2 * 1000;  /* 10 secs */
private long FASTEST_INTERVAL = 10000; /* 2 sec */

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

    mLatitudeTextView = (TextView) findViewById((R.id.latitude_textview));
    mLongitudeTextView = (TextView) findViewById((R.id.longitude_textview));

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

    mLocationManager = (LocationManager)this.getSystemService(Context.LOCATION_SERVICE);

    checkLocation(); //check whether location service is enable or not in your  phone
}

@Override
public void onConnected(Bundle bundle) {
    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;
    }

    startLocationUpdates();

    mLocation = LocationServices.FusedLocationApi.getLastLocation(mGoogleApiClient);

    if(mLocation == null){
        startLocationUpdates();
    }
    if (mLocation != null) {

        // mLatitudeTextView.setText(String.valueOf(mLocation.getLatitude()));
        //mLongitudeTextView.setText(String.valueOf(mLocation.getLongitude()));
    } else {
        Toast.makeText(this, "Location not Detected", Toast.LENGTH_SHORT).show();
    }
}

@Override
public void onConnectionSuspended(int i) {
    Log.i(TAG, "Connection Suspended");
    mGoogleApiClient.connect();
}

@Override
public void onConnectionFailed(ConnectionResult connectionResult) {
    Log.i(TAG, "Connection failed. Error: " + connectionResult.getErrorCode());
}

@Override
protected void onStart() {
    super.onStart();
    if (mGoogleApiClient != null) {
        mGoogleApiClient.connect();
    }
}

@Override
protected void onStop() {
    super.onStop();
    if (mGoogleApiClient.isConnected()) {
        mGoogleApiClient.disconnect();
    }
}

protected void startLocationUpdates() {
    // Create the location request
    mLocationRequest = LocationRequest.create()
            .setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY)
            .setInterval(UPDATE_INTERVAL)
            .setFastestInterval(FASTEST_INTERVAL);
    // Request location updates
    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);
    Log.d("reque", "--->>>>");
}

@Override
public void onLocationChanged(Location location) {

    String msg = "Updated Location: " +
            Double.toString(location.getLatitude()) + "," +
            Double.toString(location.getLongitude());
    mLatitudeTextView.setText(String.valueOf(location.getLatitude()));
    mLongitudeTextView.setText(String.valueOf(location.getLongitude() ));
    Toast.makeText(this, msg, Toast.LENGTH_SHORT).show();
    // You can now create a LatLng Object for use with maps
    LatLng latLng = new LatLng(location.getLatitude(), location.getLongitude());
}

private boolean checkLocation() {
    if(!isLocationEnabled())
        showAlert();
    return isLocationEnabled();
}

private void showAlert() {
    final AlertDialog.Builder dialog = new AlertDialog.Builder(this);
    dialog.setTitle("Enable Location")
            .setMessage("Your Locations Settings is set to 'Off'.\nPlease Enable Location to " +
                    "use this app")
            .setPositiveButton("Location Settings", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface paramDialogInterface, int paramInt) {

                    Intent myIntent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
                    startActivity(myIntent);
                }
            })
            .setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface paramDialogInterface, int paramInt) {

                }
            });
    dialog.show();
}

private boolean isLocationEnabled() {
    locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
    return locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER) ||
            locationManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER);
}

}

正如您所看到的，它是一个小代码，但我遇到了一个问题：如何将此转换为始终在后台工作？我不知道如何开始...

是否正确启动下面此代码的服务？

 @Override
 protected void onStart() {
    super.onStart();
    if (mGoogleApiClient != null) {
        mGoogleApiClient.connect();

        Intent intent =  new Intent(this, MainActivity.class);
        startService(intent);

    }
}

我希望你明白我的意思。 谢谢，祝你有愉快的一天！