从 Android 获取 GPS 位置

Question

我不知道为什么，但我无法再使用我几个月前构建的同一个应用程序获取 gps 位置。

这是简单的代码：

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);
                }
            });
        }
    }

以及清单中添加的权限：

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

如您所见，这是一个非常简单的代码。单击按钮时会出现 gps 图标，但未显示经度。为什么？你能帮助我吗？奇怪的是，正如我所说，几个月前这段代码使用完美。

Answer 1

试试这个：

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);
        }
    }
}

提取configure_button()到按钮的onClickListener。这样，您仅在需要时（单击按钮时）才请求许可。它还有助于解决用户拒绝权限的情况，因为稍后单击该按钮将再次请求权限。

还有一个Snackbar with a message telling the user why the permission is needed, along with an action请求权限。

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