从 Android 获取 GPS 位置

Question

I don't know why but I can't get gps location anymore with the same app I've builded months ago.

That's the simple code:

public class MainActivity extends AppCompatActivity {

        private Button b;
        private TextView t;
        private LocationManager locationManager;
        private LocationListener listener;


        @Override
        protected void onCreate(@Nullable Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);

            setContentView(R.layout.activity_main);

            t = (TextView) findViewById(R.id.textView);
            b = (Button) findViewById(R.id.button);

            locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);


            listener = new LocationListener() {
                @Override
                public void onLocationChanged(Location location) {
                    t.setText(Double.toString(location.getLongitude()));
                }

                @Override
                public void onStatusChanged(String s, int i, Bundle bundle) {

                }

                @Override
                public void onProviderEnabled(String s) {

                }

                @Override
                public void onProviderDisabled(String s) {

                    Intent i = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
                    startActivity(i);
                }
            };

            configure_button();
        }

        @Override
        public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
            switch (requestCode){
                case 10:
                    configure_button();
                    break;
                default:
                    break;
            }
        }

        void configure_button(){
            // first check for permissions
            if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                    requestPermissions(new String[]{Manifest.permission.ACCESS_COARSE_LOCATION,Manifest.permission.ACCESS_FINE_LOCATION,Manifest.permission.INTERNET}
                            ,10);
                }
                return;
            }
            // this code won't execute IF permissions are not allowed, because in the line above there is return statement.
            b.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    //noinspection MissingPermission
                    locationManager.requestLocationUpdates("gps", 5000, 0, listener);
                }
            });
        }
    }

And the permissions added in the manifest:

<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>

As you can see, It's a very simple code. The gps icon appears when I click the button but no longitude is shown. Why? Can you help me? The strange thing is that as I said, months ago this code use to work perfectly.

Answer 1

Try this:

public class MainActivity extends AppCompatActivity {

    private Button b;
    private TextView t;
    private LocationManager locationManager;
    private LocationListener listener;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.main_activity);

        b = (Button) findViewById(R.id.button);
        t = (TextView) findViewById(R.id.textView);

        locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);

        listener = new LocationListener() {
            @Override
            public void onLocationChanged(Location location) {
                t.setText(String.valueOf(location.getLongitude()));
            }

            @Override
            public void onStatusChanged(String s, int i, Bundle bundle) {
                //
            }

            @Override
            public void onProviderEnabled(String s) {
                //
            }

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

        b.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                configure_button();
            }
        });
    }

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

        switch (requestCode) {
            case 10:
                configure_button();
                break;
            default:
                break;
        }
    }

    void configure_button() {
        // first check for permissions
        if (ActivityCompat.checkSelfPermission(MainActivity.this, Manifest.permission.ACCESS_FINE_LOCATION)
                != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(MainActivity.this,
                ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {

            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                request_permission();
            }
        } else {
            // permission has been granted
            locationManager.requestLocationUpdates("gps", 5000, 0, listener);
        }
    }

    private void request_permission() {
        if (ActivityCompat.shouldShowRequestPermissionRationale(MainActivity.this,
                ACCESS_COARSE_LOCATION)) {

            Snackbar.make(findViewById(R.id.main_linear_layout), "Location permission is needed because ...",
                    Snackbar.LENGTH_LONG)
                    .setAction("retry", new View.OnClickListener() {
                        @Override
                        public void onClick(View view) {
                            requestPermissions(new String[]{ACCESS_COARSE_LOCATION, Manifest.permission.ACCESS_FINE_LOCATION}, 10);
                        }
                    })
                    .show();
        } else {
            // permission has not been granted yet. Request it directly.
            requestPermissions(new String[]{ACCESS_COARSE_LOCATION, Manifest.permission.ACCESS_FINE_LOCATION}, 10);
        }
    }
}

Extract configure_button() to the onClickListener of the button. This way, you only ask for the permission when it is needed (when the button is clicked). It also helps with the case where the user denies permission because clicking the button later in the future will request for the permission again.

There's also a Snackbar with a message telling the user why the permission is needed, along with an action for requesting the permission.