android - checkSelfPermission nullpointer 6.0

我有一个检查权限问题，总是在我的6.0调试中说空指针：

我究竟做错了什么

public String getGeolocation(Context context){

    try{
        int MY_PERMISSION_ACCESS_COURSE_LOCATION = 1000;

        if ( ContextCompat.checkSelfPermission(context, android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED ) {

            ActivityCompat.requestPermissions(this, new String[]{android.Manifest.permission.ACCESS_COARSE_LOCATION},
                    MY_PERMISSION_ACCESS_COURSE_LOCATION);
        }
        if ( Build.VERSION.SDK_INT >= 23 &&
                ContextCompat.checkSelfPermission( context, android.Manifest.permission.ACCESS_FINE_LOCATION ) != PackageManager.PERMISSION_GRANTED &&
                ContextCompat.checkSelfPermission( context, android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            //return 0 ;
        }
        mLocationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE); // Here is nullpointer
        //Location location = mLocationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
        Location location = mLocationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
        if(location != null && location.getTime() > Calendar.getInstance().getTimeInMillis() - 2 * 60 * 1000) {
            // Do something with the recent location fix
            //  otherwise wait for the update below
        }
        else {
            //mLocationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, this);
            mLocationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER,  0, 0, this);
        }
    }catch (Exception e){}
return geo;

}

//我使用此方法获取数据：

public void onLocationChanged(Location location) {
    if (location != null) {
        Log.v("Location Changed", location.getLatitude() + " and " + location.getLongitude());
        geo = ""+location.getLatitude() + " , " + location.getLongitude();
        mLocationManager.removeUpdates(this);
    }
}

来自Android Studio的错误异常：

java.lang.IllegalStateException: System services not available to Activities before onCreate()

我在哪里调用getGeolocation（）？

public class AlarmReceiverCustom extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
getGeolocation(context)

最佳答案

您正在为getGeolocation()提供上下文，但仍然在对象本身上调用getSystemService()。

您可能要使用传递的上下文：

mLocationManager = (LocationManager) context.getSystemService(Context.LOCATION_SERVICE);

但是您也必须考虑Receiver and Process Lifecycle：

  BroadcastReceiver对象仅在对onReceive(Context, Intent)的调用期间有效。一旦您的代码从该函数返回，系统将认为该对象已完成并且不再处于活动状态。 [...]

  这意味着对于长时间运行的操作，您通常将服务与BroadcastReceiver结合使用，以在整个操作过程中保持包含进程的活动状态。

因此，您最好重新实现应用程序的这一部分，并使用服务来更新位置。

getGeoLocation

android - checkSelfPermission nullpointer 6.0