关于Android获取GPS位置问题

Question

各位大佬，我是大二学生。最近在看《第一行代码（第一版）》时，看到GPS定位时按着书上代码打的，但是却显示工程发生错误，检查了一下代码，未能发现错误。特此求助。
注明：已在AndroidMainFest中声明网络权限和位置权限。
package com.example.school_pet;

import java.util.List;

import android.app.Activity;
import android.content.Context;
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 test_location extends Activity{
private TextView positionTextView;
private LocationManager locationManager;
private String provider;

protected void onCreate(Bundle savedInstanceState){
    super.onCreate(savedInstanceState);
    setContentView(R.layout.location_test);

    positionTextView=(TextView)findViewById(R.id.show_location);
    locationManager=(LocationManager)getSystemService(Context.LOCATION_SERVICE);

    //获取所有可用的位置提供器
    List<String>providerList=locationManager.getProviders(true);
    if(providerList.contains(LocationManager.GPS_PROVIDER)){
        provider=LocationManager.GPS_PROVIDER;
    }else if(providerList.contains(LocationManager.NETWORK_PROVIDER)){
        provider=LocationManager.NETWORK_PROVIDER;
    }else {
        Toast.makeText(this, "No location provider to use.",Toast.LENGTH_SHORT).show();
        return;
    }
    Location location=locationManager.getLastKnownLocation(provider);
    if(location !=null)
        {showLocation(location);}
    locationManager.requestLocationUpdates(provider, 5000, 1, locationListener);
}
protected void onDestroy(){
    super.onDestroy();
    if(locationManager!=null){
        locationManager.removeUpdates(locationListener);
    }
}
LocationListener locationListener=new LocationListener(){
    public void onStatusChanged(String provider,int status,Bundle extras){

    }
    public void onProviderEnabled(String provider){

    }
    public void onProviderDisabled(String provider){

    }
    public void onLocationChanged(Location location){
        showLocation(location);
    }
};
private void showLocation(Location location){
    String currentPosition="latitude is"+location.getLatitude()+"\n"+"longitude is "+location.getLongitude();
    positionTextView.setText(currentPosition);
}

}

Answer 1