android - LocationServices.FusedLocationApi.getLastLocation 在 onCreate() 方法中不起作用

Question

这是我使用相同方法的代码 - 一次是在我的 MainActivity 中的 onCreate() 期间，一次是在用户单击按钮后

// Below code not working during onCreate
 StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
    StrictMode.setThreadPolicy(policy);

    // Create an instance of GoogleAPIClient. From Google API demo code
    if (mGoogleApiClient == null) {
        mGoogleApiClient = new GoogleApiClient.Builder(this)
                .addConnectionCallbacks(this)
                .addOnConnectionFailedListener(this)
                .addApi(LocationServices.API)
                .build();
    }

    startLocationOnScreen.setText(getCurrentLocationViaPhoneLocation());

// Surprisingly same method works if it's called after a button press!

        startButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

                           startLocationOnScreen.setText(getCurrentLocationViaPhoneLocation());

那为什么会这样呢？我基本上想在加载应用程序时获取用户的当前位置，而不是强制用户按下按钮来获取相同的位置。

getCurrentLocationViaPhoneLocation() 方法的实现——(大部分取自 Google API 文档)

protected String getCurrentLocationViaPhoneLocation() {

    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 "Error - location services not available!";
    }
    startLocation = LocationServices.FusedLocationApi.getLastLocation(
            mGoogleApiClient);
    if (startLocation != null) {
        Log.e("We are at ", String.valueOf(startLocation.getLatitude()));
        Log.e("We are at ", String.valueOf(startLocation.getLongitude()));

        Geocoder geocoder = new Geocoder(this, Locale.getDefault());

        try {
            List<Address> addressList = geocoder.getFromLocation(startLocation.getLatitude(), startLocation.getLongitude(), 1);

            if (addressList != null && addressList.size() > 0) {


                currentCity = addressList.get(0).getLocality();


                Address address = addressList.get(0);
                StringBuilder sb = new StringBuilder();
                for (int i = 0; i < address.getMaxAddressLineIndex(); i++) {
                    sb.append(address.getAddressLine(i)).append("\n");
                }

                return (sb.toString());

            }

        } catch (IOException e) {
            e.printStackTrace();
        }


    }

    return ("Error - current location unavailable!");
}

编辑: 我得到: Error - current location unavailable! during onCreate() 这意味着 startLocation==null 当方法在 onCreate() 期间被调用时。

Answer 1

我怀疑在您第一次调用该方法时(即在 onCreate 期间)GoogleApiClient 尚未连接。

您已经调用了 Builder 的 addConnectionCallbacks 方法。因此，您应该在 Activity 中实现 GoogleApiClient.ConnectionCallbacks 的 onConnected(Bundle) 方法。在这里而不是在 onCreated 中调用 getCurrentLocationViaPhoneLocation 方法，然后您可以确定 GoogleApiClient 已正确连接。

如果 onConnected 方法没有被调用，尝试在 onCreate 中创建实例后添加 mGoogleApiClient.connect()。

希望对您有所帮助!