java - onLocationChanged() 不会自动调用

Question

如果我理解正确，在这段代码中，我的代码 onLocationChanged 方法应该每 1m 或 0.4sec 自动调用一次，因为我设置了 locationManager.requestLocationUpdates(provider, 400, 1 ，这个)；

但是什么也没发生!当我按下按钮时，onLocationChanged 被调用。没有任何内容自动调用，无论是每 1 秒还是 0.4 秒。有人可以帮忙吗？

public class MainActivity extends AppCompatActivity implements LocationListener {
LocationManager locationManager;
public static final int MY_PERMISSIONS_REQUEST_LOCATION = 99;
String provider;

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

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

    provider = locationManager.getBestProvider(new 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.
        return;
    }
    Location location = locationManager.getLastKnownLocation(provider);

    if (location != null) {

        Log.i("Location Info", "Location achieved!");
        Toast.makeText(getApplicationContext(),"Location achieved!",Toast.LENGTH_SHORT).show();

    } else {

        Log.i("Location Info", "No location :(");
        Toast.makeText(getApplicationContext(),"No location :(",Toast.LENGTH_SHORT).show();

    }

}
public boolean checkLocationPermission() {
    if (ContextCompat.checkSelfPermission(this,
            Manifest.permission. ACCESS_FINE_LOCATION)
            != PackageManager.PERMISSION_GRANTED) {

        // Should we show an explanation?
        if (ActivityCompat.shouldShowRequestPermissionRationale(this,
                Manifest.permission. ACCESS_FINE_LOCATION)) {

            // Show an explanation to the user *asynchronously* -- don't block
            // this thread waiting for the user's response! After the user
            // sees the explanation, try again to request the permission.
            new AlertDialog.Builder(this)
                    .setTitle("Title")
                    .setMessage("Text")
                    .setPositiveButton("Ok", new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialogInterface, int i) {
                            //Prompt the user once explanation has been shown
                            ActivityCompat.requestPermissions(MainActivity.this,
                                    new String[]{Manifest.permission. ACCESS_FINE_LOCATION},
                                    MY_PERMISSIONS_REQUEST_LOCATION);
                        }
                    })
                    .create()
                    .show();


        } else {
            // No explanation needed, we can request the permission.
            ActivityCompat.requestPermissions(this,
                    new String[]{Manifest.permission. ACCESS_FINE_LOCATION},
                    MY_PERMISSIONS_REQUEST_LOCATION);
        }
        return false;
    } else {
        return true;
    }
}
@Override
public void onRequestPermissionsResult(int requestCode,
                                       String permissions[], int[] grantResults) {
    switch (requestCode) {
        case MY_PERMISSIONS_REQUEST_LOCATION: {
            // 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(provider, 400, 1, this);
                }

            } else {

                // permission denied, boo! Disable the
                // functionality that depends on this permission.

            }
            return;
        }

    }
}



@Override
protected void onResume() {
    super.onResume();

    checkLocationPermission();


}

@Override
protected void onPause() {
    super.onPause();

    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.
        return;
    }
    locationManager.removeUpdates(this);

}

@Override
public void onLocationChanged(Location location) {

    Double lat = location.getLatitude();
    Double lng = location.getLongitude();

    Log.i("Location info: Lat", lat.toString());
    Log.i("Location info: Lng", lng.toString());
    Toast.makeText(getApplicationContext(),"Location info: Lat"+lat.toString(),Toast.LENGTH_SHORT).show();
    Toast.makeText(getApplicationContext(),"Location info: Lng"+lng.toString(),Toast.LENGTH_SHORT).show();

}

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

}

@Override
public void onProviderEnabled(String provider) {

}

@Override
public void onProviderDisabled(String provider) {

}


public void getLocation(View view) {

    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.
        return;
    }
    Location location = locationManager.getLastKnownLocation(provider);

    onLocationChanged(location);
}
}

Answer 1

如果已授予权限，只需修改您的 onResume() 方法重写即可请求位置更新。

如果尚未授予权限，则 requestLocationUpdates() 调用将在 onRequestPermissionsResult() 方法重写中发生(如果用户接受权限请求)。

如果之前已授予该权限，您可以立即调用 requestLocationUpdates()。

@Override
protected void onResume() {
    super.onResume();

    if (checkLocationPermission()) {
        locationManager.requestLocationUpdates(provider, 400, 1, this);
    }
}