问题描述
我正在尝试从GPS获取经纬度
我找到了以下链接：
How to get Android GPS location
https://www.vogella.com/tutorials/AndroidLocationAPI/article.html
这是我的代码：
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;
import android.Manifest;
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.Bundle;
import android.widget.TextView;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity implements LocationListener {
private TextView latituteField;
private TextView longitudeField;
private LocationManager locationManager;
private String provider;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
latituteField = (TextView) findViewById(R.id.TextView02);
longitudeField = (TextView) findViewById(R.id.TextView04);
// Get the location manager
locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
// Define the criteria how to select the locatioin provider -> use
// default
Criteria criteria = new Criteria();
provider = locationManager.getBestProvider(criteria,false);
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.
Location location = locationManager.getLastKNownLocation(provider);
if (location != null) {
System.out.println("Provider " + provider + " has been selected.");
onLocationChanged(location);
} else {
latituteField.setText("Location not available");
longitudeField.setText("Location not available");
}
return;
}
}
@Override
protected void onResume() {
super.onResume();
if (ActivityCompat.checkSelfPermission(this,// int[] grantResults)
// to handle the case where the user grants the permission. See the documentation
// for ActivityCompat#requestPermissions for more details.
locationManager.requestLocationUpdates(provider,400,1,this);
return;
}
}
@Override
protected void onPause() {
super.onPause();
locationManager.removeUpdates(this);
}
@Override
public void onLocationChanged(Location location) {
double lat = (double) (location.getLatitude());
double lng = (double) (location.getLongitude());
latituteField.setText(String.valueOf(lat));
longitudeField.setText(String.valueOf(lng));
}
@Override
public void onStatusChanged(String provider,int status,Bundle extras) {
}
@Override
public void onProviderEnabled(String provider) {
Toast.makeText(this,"Enabled new provider " + provider,Toast.LENGTH_SHORT).show();
}
@Override
public void onProviderdisabled(String provider) {
Toast.makeText(this,"disabled provider " + provider,Toast.LENGTH_SHORT).show();
}}
当我运行此应用程序时，该应用程序停止
这是错误：
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.locationmanagertutorial,PID: 13737
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.locationmanagertutorial/com.example.locationmanagertutorial.MainActivity}: java.lang.IllegalArgumentException: invalid provider: null
at android.app.ActivityThread.performlaunchActivity(ActivityThread.java:2957)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3032)
at android.app.ActivityThread.-wrap11(UnkNown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1696)
at android.os.Handler.dispatchMessage(Handler.java:105)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6944)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:327)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1374)
Caused by: java.lang.IllegalArgumentException: invalid provider: null
at android.location.LocationManager.checkProvider(LocationManager.java:2098)
at android.location.LocationManager.getLastKNownLocation(LocationManager.java:1199)
at com.example.locationmanagertutorial.MainActivity.onCreate(MainActivity.java:47)
at android.app.Activity.performCreate(Activity.java:7183)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1220)
at android.app.ActivityThread.performlaunchActivity(ActivityThread.java:2910)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3032)
at android.app.ActivityThread.-wrap11(UnkNown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1696)
at android.os.Handler.dispatchMessage(Handler.java:105)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6944)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:327)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1374)
如果有可能我想在没有互联网的情况下从GPS获取纬度和经度。
解决方法
- 将以下权限放入android清单（用于LocationManager.GPS_PROVIDER），并使用checkSelfPermission方法照常请求权限。
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="yourpackage.com">
...
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
...
- 然后您需要请求位置更新，如下所示：
LocationManager locationManager = (LocationManager)context.getSystemService(Context.LOCATION_SERVICE);
LocationListener locationListener = new LocationListener();
try
{
if (locationManager != null) {
locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER,10000,locationListener);
}
} catch (Exception e) {
//logger.error("Can't access GPS_PROVIDER",e);
}
- 这是LocationListener类：
private class LocationListener implements android.location.LocationListener {
@Override
public void onLocationChanged(Location location) {
//logger.trace(String.format("Location changed: provider=%1$s,lat = %2$.4f,lon = %3$.4f,time = %4$tF %4$tT",location.getProvider(),location.getLatitude(),location.getLongitude(),new Date(location.getTime())));
}
@Override
public void onProviderDisabled(String provider) {
// logger.trace(provider + " disabled");
}
@Override
public void onProviderEnabled(String provider) {
// logger.trace(provider + " enabled");
}
@Override
public void onStatusChanged(String provider,int status,Bundle extras) {
// logger.trace(provider + " sent changed to " + Integer.toString(status));
}
}
检查权限后，您应该进行与位置相关的查询。最好创建另一种启动位置服务的方法，例如
private void startLocationservice(){
Criteria criteria = new Criteria();
provider = locationManager.getBestProvider(criteria,false);
if(provider == null){
provider = LocationManager.GPS_PROVIDER;
}
locationManager.requestLocationUpdates(provider,400,1,this);
}
现在在onCreate中添加此代码
if (ActivityCompat.checkSelfPermission(this,Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this,Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
startLocationservice();
}
else{
String [] missingPermissions = {Manifest.permission.ACCESS_FINE_LOCATION,Manifest.permission.ACCESS_COARSE_LOCATION };
ActivityCompat.requestPermissions(activity,missingPermissions,PERMISSIONS_REQUEST_CODE)
}
添加回调活动
public void onRequestPermissionsResult(int requestCode,int[] grantResults){
if (ActivityCompat.checkSelfPermission(this,Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
startLocationservice();
}
}
从您的活动中删除重复的代码