getLastKnownLocation 第一次 return 空问题

Question

我正在开发一个简单的 android 位置应用程序，但我有点小麻烦。（也很抱歉我的英语不好。）

我想通过单击按钮获取当前位置，但 getLastKnownLocation returns 第一次全部为空。

而且，如果我首先打开 google 地图并在地图上显示我的当前位置，然后我通过背景，然后打开我自己的应用程序，请单击可用的按钮。但我不想要这种方式，我只想在我的应用程序上提供位置而不是这种方式。

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Object clipboardService = getSystemService(CLIPBOARD_SERVICE);
    final ClipboardManager clipboardManager = (ClipboardManager) clipboardService;
    tvEnlem = (TextView) findViewById(R.id.textViewEnlem);
    tvBoylam = (TextView) findViewById(R.id.textViewBoylam);
    retrieveLocationButton = (Button) findViewById(R.id.buttonNeredeyim);
    locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);

    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(this, new String[]{android.Manifest.permission.ACCESS_FINE_LOCATION, android.Manifest.permission.ACCESS_COARSE_LOCATION}, 101);
        //    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;
    }


    retrieveLocationButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            showCurrentLocation();
        }
    });

}

protected void showCurrentLocation() {

    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(this, new String[]{android.Manifest.permission.ACCESS_FINE_LOCATION, android.Manifest.permission.ACCESS_COARSE_LOCATION}, 101);
        //    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 = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
    if (location != null) {
        String message = String.format(
                "Current Location \n Longitude: %1$s \n Latitude: %2$s",
                location.getLongitude(), location.getLatitude()
        );
        Toast.makeText(MainActivity.this, message,
                Toast.LENGTH_LONG).show();

        this.tvBoylam.setText(String.valueOf(location.getLongitude()));
        this.tvEnlem.setText(String.valueOf(location.getLatitude()));

    }
    else{

        Toast.makeText(MainActivity.this,"LOKASYON BİLGİLERİ BOŞ",
                Toast.LENGTH_SHORT).show();

    }


}

private class MyLocationListener implements LocationListener {

    public void onLocationChanged(Location location) {
        String message = String.format(
                "New Location \n Longitude: %1$s \n Latitude: %2$s",
                location.getLongitude(), location.getLatitude()
        );
        Toast.makeText(MainActivity.this, message, Toast.LENGTH_LONG).show();
    }

    public void onStatusChanged(String s, int i, Bundle b) {
        Toast.makeText(MainActivity.this, "Provider status changed",
                Toast.LENGTH_LONG).show();
    }

    public void onProviderDisabled(String s) {
        Toast.makeText(MainActivity.this,
                "Provider disabled by the user. GPS turned off",
                Toast.LENGTH_LONG).show();
    }

    public void onProviderEnabled(String s) {
        Toast.makeText(MainActivity.this,
                "Provider enabled by the user. GPS turned on",
                Toast.LENGTH_LONG).show();
    }

}



}

如何获取没有空值的位置？

Answer 1

这不是错误，而只是 Google 政治。 getLastKnowLocation() 方法 return google 服务检索的最后一个位置。正如 Google 文档所说：

The location object may be null in the following situations:

Location is turned off in the device settings. The result could be null even if the last location was previously retrieved because
disabling location also clears the cache.

The device never recorded its location, which could be the case of a new device or a device that has been restored to factory settings.

Google Play services on the device has restarted, and there is no active Fused Location Provider client that has requested location after the services restarted.

这就是为什么如果您从 Google 地图切换到您的应用程序，您可以获得最后的位置。要在不从应用程序传递到其他应用程序的情况下获得实际位置，您需要实现一个新的客户端并自行请求位置更新。有关详细信息，请参阅 Receiving Location Updates。

我希望我已经澄清了你的每一个疑问。否则，请不要犹豫写:)

getLastKnownLocation 第一次 return 空问题

getLastKnownLocation first time return null issue

java

android

location-services