LocationListener 没有提供任何速度更新

Question

我正在尝试使用LocationListener 获取我的 GPS 速度。

我在第一次启动应用程序时请求许可，然后授予许可，“onLocationChanged()”立即显示祝酒词，但不再显示。

我在手机上激活了位置信息。 但我没有收到更多位置更新。

我很抱歉倾倒了我所有的代码，但我不确定要显示什么。

有人知道我在这里缺少什么吗？

package com.example.username.yaddayadda;

import android.Manifest;
import android.annotation.TargetApi;
import android.app.Activity;
import android.content.Context;
import android.content.pm.PackageManager;
import android.location.Location;
import android.location.LocationManager;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.TextView;
import android.location.GpsStatus;
import android.location.LocationListener;
import android.location.Location;
import android.widget.Toast;
import java.util.Formatter;
import java.util.Locale;

@TargetApi(23)
public class MainActivity extends Activity implements LocationListener{

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

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

    try {
        if (checkIfPermissionIsGranted()){
            Toast toast = Toast.makeText(getApplicationContext(), "Permission is granted for fine and coarse location", Toast.LENGTH_LONG);
            toast.show();
            locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, this);
            locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, this);
        }
        else {
            ActivityCompat.requestPermissions(this, new String[] {
                            Manifest.permission.ACCESS_FINE_LOCATION,
                            Manifest.permission.ACCESS_COARSE_LOCATION },
                    1);

            if(checkIfPermissionIsGranted()){
                Toast toast = Toast.makeText(getApplicationContext(), "Permission was granted for fine and coarse location", Toast.LENGTH_LONG);
                toast.show();

                locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, this);
                locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, this);
            } else {
                Toast toast = Toast.makeText(getApplicationContext(), "Permission was denied for fine and coarse location", Toast.LENGTH_LONG);
                toast.show();
            }
        }
    } catch(SecurityException e){
        Context context = getApplicationContext();
        CharSequence text = "Got exception: \n" + e.getMessage();
        int duration = Toast.LENGTH_LONG;

        Toast toast = Toast.makeText(context, text, duration);
        toast.show();
    }
    this.onLocationChanged(null);
}

private boolean checkIfPermissionIsGranted(){
    return (ContextCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED
            && ContextCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_COARSE_LOCATION) == PackageManager.PERMISSION_GRANTED);
}

@Override
public void onLocationChanged(Location location) {
    TextView txt = (TextView) this.findViewById(R.id.txtCurrentSpeed);
    Toast toast = Toast.makeText(getApplicationContext(), "onLocationChanged()", Toast.LENGTH_SHORT);
    toast.show();

    if(location==null){
        txt.setText("-.- m/s");
    }
    else {
        if(location.hasSpeed()){
            float nCurrentSpeed = location.getSpeed();
            txt.setText(nCurrentSpeed + " m/s");
        } else {
            txt.setText("0.0 m/s");
        }
    }
}

@Override
public void onStatusChanged(String provider, int status, Bundle extras) {
    Toast toast = Toast.makeText(getApplicationContext(), "onStatusChanged()", Toast.LENGTH_SHORT);
    toast.show();
}

@Override
public void onProviderEnabled(String provider) {
    Toast toast = Toast.makeText(getApplicationContext(), "onProviderEnabled()", Toast.LENGTH_SHORT);
    toast.show();
}

@Override
public void onProviderDisabled(String provider) {
    Toast toast = Toast.makeText(getApplicationContext(), "onProviderdisabled()", Toast.LENGTH_SHORT);
    toast.show();
}
}

Answer 1

“onLocationChanged()”立即显示祝酒词，但不再显示。

您没有收到任何位置更新，但您在此处自己调用此函数

// toast because of this , so no need of this , remove this call
this.onLocationChanged(null); 

但是我没有更多的位置更新。

因为第一次，您拥有权限，然后在授予权限后，您需要再次从onRequestPermissionsResult 执行位置请求代码。

所以你需要覆盖onRequestPermissionsResult，一旦你获得了权限，然后requestLocationUpdates就像

@Override
public void onRequestPermissionsResult(int requestCode,
                                       String permissions[], int[] grantResults) {
    switch (requestCode) {
        case 1: {
            // If request is cancelled, the result arrays are empty.
            if (grantResults.length > 0
                    && grantResults[0] == PackageManager.PERMISSION_GRANTED) {

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

                    //Request location updates:
                    locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 10, 1000*60, this);
                }

            } else {

                // permission denied, Disable the
                // functionality that depends on this permission.
            }
            return;
        }

    }
}

注意：向两个提供商请求位置是理想的，只需使用最好的一个，您可以将您的位置请求代码移动到单独的函数中，并在需要时调用它。

参考

getBestLocation()