需要从onLocationChanged获得更新的位置/数据

Question

只是一个警告:我真的不为我编写的这段代码感到骄傲，但无论如何我都需要它来工作。别太苛刻地评价我。

嘿，各位，我正在编写一个速度表android应用程序，我遇到了一个基本的问题。我需要使用Android定位服务来计算两个GPS坐标之间的距离(我知道融合定位提供商更优越，但请容忍这一点)。

位置侦听器类位于一个名为CurrentLocationListener.java的Java文件中。到目前为止，我已经能够获得两个坐标，并在上面的java文件中获得更新的坐标和旧的坐标之间的距离，但是我需要一些方法将它传递到MainActivity.java文件，在那里我可以用所述的距离更新UI。这两个java文件的代码如下：

MainActivity.java

package com.example.speedometer;

import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;
import androidx.core.content.ContextCompat;

import android.Manifest;
import android.annotation.SuppressLint;
import android.content.Context;
import android.content.pm.PackageManager;
import android.location.Location;
import android.location.LocationManager;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;
import android.widget.Toast;
import java.lang.Thread;

public class MainActivity extends AppCompatActivity {

    CurrentLocationListener currentLocationListener;
    LocationManager locationManager;
    TextView textCurrentSpeed, textOdometer, textAvgSpeed;
//    MainActivity mainActivity;

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

        currentLocationListener = new CurrentLocationListener();
        textCurrentSpeed = findViewById(R.id.dispCurrentSpeed);
        textOdometer = findViewById(R.id.dispOdometer);
        textAvgSpeed = findViewById(R.id.dispAvgSpeed);

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

        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED)
        {
            Toast.makeText(this, "Location permission not granted. Please grant permission.", Toast.LENGTH_LONG).show();
            alertbox();
        }
        locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 2000, 5, currentLocationListener);
    }

    protected void alertbox()
    {
        if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED)
        {
            ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.ACCESS_FINE_LOCATION, Manifest.permission.ACCESS_COARSE_LOCATION}, 1);
        }
    }

    public void updateLocation() {
        Location location = null;
        double[] coords = new double[2];

        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            Toast.makeText(this, "Permission to gps not granted. Grant permissions and try again or restart the application.", Toast.LENGTH_LONG).show();
            alertbox();
        }
        else {
            location = locationManager.getLastKnownLocation(Context.LOCATION_SERVICE);
        }

        locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 5000, 5, currentLocationListener);

        if (location == null)
        {
            location = currentLocationListener.getLocation();
        }
        else {
            Toast.makeText(this, "unknown location", Toast.LENGTH_LONG).show();
        }

    }

    @SuppressLint("SetTextI18n")
    protected void main()
    {
        double oldlat, newlat, oldlong, newlong;
        double[] coords;
        double odometer = 0, timeElapsed = 0, distanceTravelled, currentSpeed, avgSpeed;
        double startTime, endTime;

//        coords = updateLocation();
//        oldlong = coords[0];
//        oldlat = coords[1];



//        while(true)
//        {
//            startTime = System.nanoTime();
//            try
//            {
//                Thread.sleep(10000);
//            } catch (InterruptedException e)
//            {
//                e.printStackTrace();
//            }
//
//            coords = updateLocation();
//
//            newlong = coords[0];
//            newlat = coords[1];
//            System.out.println(newlat + " " + newlong);
//
//            distanceTravelled = earthDistance(oldlat, oldlong, newlat, newlong);
//
//            odometer += distanceTravelled;
//
//            endTime = System.nanoTime();
//
//            timeElapsed += (endTime - startTime);
//            currentSpeed = (distanceTravelled)/((endTime-startTime)/1e9); // m/s to km/hr
//            avgSpeed = (odometer/1000)/(timeElapsed/1e9);
//
////            System.out.println("odo: " + odometer);
////            System.out.println("currspeed: " + currentSpeed);
//            System.out.println("dist: " + distanceTravelled);
//
//            textCurrentSpeed.setText(currentSpeed + " m/s");
//            textOdometer.setText((odometer) + " m");
//            textAvgSpeed.setText(avgSpeed + " km/hr");
//
//            oldlat = newlat;
//            oldlong = newlong;
//        }
    }


    protected double earthDistance(double lat1, double lon1, double lon2, double lat2)
    {

        final double R = 6371e3; // Radius of the earth

        double latDistance = Math.toRadians(lat2 - lat1);
        double lonDistance = Math.toRadians(lon2 - lon1);
        double a = Math.sin(latDistance / 2) * Math.sin(latDistance / 2)
                + Math.cos(Math.toRadians(lat1)) * Math.cos(Math.toRadians(lat2))
                * Math.sin(lonDistance / 2) * Math.sin(lonDistance / 2);
        double c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));

        return R * c;
    }

    public void setTextFields(double distance)
    {
        System.out.println(distance);
    }

    public void buttonStart(View MainActivity)
    {
//        main();
        updateLocation();
    }
}

CurrentLocationListener.java

package com.example.speedometer;

import android.location.Location;
import android.location.LocationListener;
import android.os.Bundle;
import android.os.Message;
import android.widget.TextView;
import android.view.View;
import android.content.Context;

public class CurrentLocationListener implements LocationListener {
    Location myLocation;
    double templat = 404, templong = 404;
    double odometer = 0, totalTime = 0, currentDist, currentSpeed, avgSpeed;
    TextView textCurrentSpeed, textOdometer, textAvgSpeed;
    MainActivity mainActivity;


    public Location getLocation()
    {
        return myLocation;
    }

    @Override
    public void onLocationChanged(Location location)
    {
//        textCurrentSpeed = mainActivity.findViewById(R.id.dispCurrentSpeed);
//        textOdometer = mainActivity.findViewById(R.id.dispOdometer);
//        textAvgSpeed = mainActivity.findViewById(R.id.dispAvgSpeed);
        double startTime, endTime;
        myLocation = location;
        if (templat == 404 && templong == 404)
        {
            templat = location.getLatitude();
            templong = location.getLongitude();
        }
        else
        {
            currentDist = earthDistance(location.getLatitude(), location.getLongitude(), templong, templat);
            templat = location.getLatitude();
            templong = location.getLongitude();
            System.out.println("dist: " + currentDist);
            odometer += currentDist;
            totalTime += 10;
            currentSpeed = currentDist/10;
            avgSpeed = odometer/totalTime;

            mainActivity.setTextFields(odometer);
//            textCurrentSpeed.setText(currentSpeed + " m/s");
        }
//        System.out.println("update");
//        System.out.println(location.getLatitude() + " " + location.getLongitude());
    }

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

    }

    @Override
    public void onProviderEnabled(String provider) {

    }

    @Override
    public void onProviderDisabled(String provider) {

    }

    protected double earthDistance(double lat1, double lon1, double lon2, double lat2)
    {

        final double R = 6371e3; // Radius of the earth

        double latDistance = Math.toRadians(lat2 - lat1);
        double lonDistance = Math.toRadians(lon2 - lon1);
        double a = Math.sin(latDistance / 2) * Math.sin(latDistance / 2)
                + Math.cos(Math.toRadians(lat1)) * Math.cos(Math.toRadians(lat2))
                * Math.sin(lonDistance / 2) * Math.sin(lonDistance / 2);
        double c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));

        return R * c;
    }
}

我的主要目标是用计算值更新TextView字段，比如里程表读数。我知道有很多重复的代码和评论，但老实说，我已经超出了我的深度，迫切需要帮助。如果还需要更多的信息，请告诉我。提前谢谢。

Answer 1

您可以让您的MainActivity实现LocationListener：

public class MainActivity 
extends 
AppCompactActivity implements 
LocationListener {
//Rest of the code

@Override
public void 
onLocationChanged(Location 
location){
//do your stuff       
 }

@Override
public void onStatusChanged(String 
provider, int status, Bundle 
extras) {
//do your stuff
}

@Override
public void 
onProviderEnabled(String provider) 
{
//do your stuff
}

@Override
public void 
onProviderDisabled(String 
provider) {
//do your stuff
}
    }