重新打开应用后，LocationManager将无法启动

Question

我正在做一个项目，该项目会定期确定手机的坐标并将其上载到数据库中。 我使用的代码是：

public class Activity2 extends AppCompatActivity {

private LocationManager locm;
private LocationListener locl;
private Geocoder geocoder;
public TextView text, position;
public double lat, lon;
public String city;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_2);
    text = (TextView) findViewById(R.id.textView4);
    position = (TextView) findViewById(R.id.textView5);

    text.setText("Seriale: " + Build.SERIAL + "\nNome: " + Build.MANUFACTURER + " " + Build.PRODUCT);
    geocoder = new Geocoder(getApplicationContext(), Locale.getDefault());
    locm = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
    locl = new LocationListener(){
        @Override
        public void onLocationChanged(Location location) {
            try{
                lat=location.getLatitude();
                lon=location.getLongitude();
                DateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
                String date = df.format(Calendar.getInstance().getTime());
                List<Address> la = geocoder.getFromLocation(lat, lon, 1);
                if (la != null & la.size() > 0) {
                    Address address = la.get(0);
                    city = address.getLocality();
                }
                else
                {
                    city="UNKNOWN";
                }
                MainActivity.st.executeUpdate("INSERT INTO position VALUES ('" + Build.SERIAL + "', '" + date + "', '" + lat + "', '" + lon + "', '" +city + "')");
                position.setText(city);
            } catch (Exception a){

            }
        }

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

        }

        @Override
        public void onProviderEnabled(String provider) {

        }

        @Override
        public void onProviderDisabled(String provider) {
            Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
            startActivity(intent);
        }

    };

    if (Build.VERSION.SDK_INT>=Build.VERSION_CODES.M) {
        if(checkSelfPermission(Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
           requestPermissions(new String[]{
                   Manifest.permission.ACCESS_FINE_LOCATION,Manifest.permission.ACCESS_COARSE_LOCATION,
                   Manifest.permission.INTERNET
           }, 10);
            return;
        }
    }else{
        locm.requestLocationUpdates("gps", 5000, 0, locl);
    }
}

@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
    switch (requestCode){

        case 10:
            if(grantResults.length>0 && grantResults[0]==PackageManager.PERMISSION_GRANTED) {
                try{
                    locm.requestLocationUpdates("gps", 5000, 0, locl);
                }catch (SecurityException e){

                }
            }
    }
}

从一个干净的开始（之前没有保存过有关应用程序的缓存/数据），它运行良好并且可以按预期工作：

• 启动第一个简单登录的活动（如果usertext = user $$ passtext = text启动Activity2 ）
• Activity2要求许可（如果禁用，则要求GPS）
• 等待GPS找到其第一个位置
• 每5秒钟上传一次职位

但是，如果我关闭该应用程序（不按后退按钮，而是从RAM中清除它），然后尝试再次打开它，则在启动Activity2后，它不再要求我启用GPS，即使它不再显示位置，它已经启用。 恢复工作的唯一方法是清除内部存储内存中的数据。

我怎么解决这个问题？ 谢谢。

Answer 1

问题是当Build.VERSION.SDK_INT >= Build.VERSION_CODES.M为true并且您已经具有必需的权限时，您不调用requestLocationUpdates() 。

请尝试以下操作：

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
    if (checkSelfPermission(Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED
                    && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
        requestPermissions(new String[] { Manifest.permission.ACCESS_FINE_LOCATION, Manifest.permission.ACCESS_COARSE_LOCATION,
                        Manifest.permission.INTERNET }, 10);
        return;
    } else {
        // you are missing this else block
        locm.requestLocationUpdates("gps", 5000, 0, locl);
    }
} else {
    locm.requestLocationUpdates("gps", 5000, 0, locl);
}