Question

我处于这样一种情况：我必须通过GSMCellLocation获取位置，即经度和纬度，因此我尝试以下方式：

  ...
  TelephonyManager tm = (TelephonyManager) context.getSystemService(Context.TELEPHONY_SERVICE);
  location = (GsmCellLocation) tm.getCellLocation();
  cid = location.getCid();
  lac = location.getLac();
  ...

但应用程序崩溃并给我NPE。我通过日志和调试检查了它，它显示getCellLocation返回null因此我无法获得cid和lac。 Google Docs中此方法的签名就是这样说的：

Returns the current location of the device. Return null if current location is not available.

现在我的问题是，如何在使用此方法之前获取当前位置，以使其不为空。因为在我的情况下，我尝试将此作为GPS和Network的替代方式来获取位置。请更新并感谢任何帮助。

Answer 1

在ACCESS_COARSE_LOCATION

中添加此权限：ACCESS_FINE_LOCATION或manifest.xml

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

Answer 2

从TelephonyManager起，它可能与LTE有关：

如果设备中只有一个无线电且该无线电具有LTE连接，则此方法将返回null ...

Answer 3

如果当前位置不可用，则getCellLocation（）返回null。请查看

Telephonymanager

另外，请检查手机设置中是否存在基带类型信息。

以下代码与我合作您可以测试

      TelephonyManager telephonyManager = (TelephonyManager)getSystemService(Context.TELEPHONY_SERVICE);
      GsmCellLocation cellLocation = (GsmCellLocation)telephonyManager.getCellLocation();

      int cid = cellLocation.getCid();
      int lac = cellLocation.getLac();
      textGsmCellLocation.setText(cellLocation.toString());
      textCID.setText("gsm cell id: " + String.valueOf(cid));
      textLAC.setText("gsm location area code: " + String.valueOf(lac));

Answer 4

在清单文件中，我添加了粗略，精细和读取手机状态的权限并在设备上运行。

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

现在添加以下代码：

private void check_ReadPhoneState_Permission() {
    // Here, thisActivity is the current activity
    if (ContextCompat.checkSelfPermission(this,
            android.Manifest.permission.READ_PHONE_STATE)
            != PackageManager.PERMISSION_GRANTED) {

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

            // 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.

        } else {

            // No explanation needed, we can request the permission.

            ActivityCompat.requestPermissions(this,
                    new String[]{android.Manifest.permission.READ_PHONE_STATE},
                    MY_PERMISSIONS_REQUEST_READ_PHONE_STATE);

            // MY_PERMISSIONS_REQUEST_READ_PHONE_STATE is an
            // app-defined int constant. The callback method gets the
            // result of the request.
        }
    }
}

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

        // Should we show an explanation?
        if (ActivityCompat.shouldShowRequestPermissionRationale(this,android.Manifest.permission.ACCESS_FINE_LOCATION)
                && ActivityCompat.shouldShowRequestPermissionRationale(this,android.Manifest.permission.ACCESS_COARSE_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(R.string.title_location_permission)
                    .setMessage(R.string.text_location_permission)
                    .setPositiveButton(R.string.ok, new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialogInterface, int i) {
                            //Prompt the user once explanation has been shown
                            ActivityCompat.requestPermissions(PhoneDetailsMain.this,
                                    new String[]{android.Manifest.permission.ACCESS_FINE_LOCATION},
                                    MY_PERMISSIONS_REQUEST_LOCATION);

                            ActivityCompat.requestPermissions(PhoneDetailsMain.this,
                                    new String[]{android.Manifest.permission.ACCESS_COARSE_LOCATION},
                                    MY_PERMISSIONS_REQUEST_COARSE_LOCATION);
                        }
                    })
                    .create()
                    .show();


        } else {
            // No explanation needed, we can request the permission.
            ActivityCompat.requestPermissions(this,
                    new String[]{android.Manifest.permission.ACCESS_FINE_LOCATION},
                    MY_PERMISSIONS_REQUEST_LOCATION);
            ActivityCompat.requestPermissions(this,
                    new String[]{android.Manifest.permission.ACCESS_COARSE_LOCATION},
                    MY_PERMISSIONS_REQUEST_COARSE_LOCATION);
        }
        return false;
    } else {
        return true;
    }
}

@Override
public void onRequestPermissionsResult(int requestCode,
                                       String permissions[], int[] grantResults) {
    switch (requestCode) {
        case 100: {
            // If request is cancelled, the result arrays are empty.
            if (grantResults.length > 0
                    && grantResults[0] == PackageManager.PERMISSION_GRANTED) {

                // permission was granted, yay! Do the
                // contacts-related task you need to do.

            } else {

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

        // other 'case' lines to check for other
        // permissions this app might request
        case 200: {
            // 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,
                        android.Manifest.permission.ACCESS_FINE_LOCATION)
                        == PackageManager.PERMISSION_GRANTED) {

                }

            } else {

                // permission denied, boo! Disable the
                // functionality that depends on this permission.
            }
        }
        case 300: {
            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,
                        android.Manifest.permission.ACCESS_COARSE_LOCATION)
                        == PackageManager.PERMISSION_GRANTED) {

                }

            } else {

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

TelephonyManager.getCellLocation（）返回null？

4 个答案: