尝试检查权限时出现NullPointerException

我正在尝试检查用户是否启用了android.Manifest.permission.ACCESS_FINE_LOCATION。 运行应用程序时，出现NullPointerException错误。

包dtt.romano.rsrpechhulp;

import android.app.Activity; import android.content.Context; import android.content.IntentSender; import android.content.pm.PackageManager; import android.location.Location; import android.os.Bundle; import android.support.annotation.NonNull; import android.support.v4.app.ActivityCompat; import android.util.Log; import com.google.android.gms.common.ConnectionResult; import com.google.android.gms.common.api.GoogleApiClient; import com.google.android.gms.location.LocationListener; import com.google.android.gms.location.LocationRequest; import com.google.android.gms.location.LocationServices; public class LocationProvider extends MainActivity implements GoogleApiClient.ConnectionCallbacks, GoogleApiClient.OnConnectionFailedListener,LocationListener { public abstract interface LocationCallback { public void handleNewLocation(Location location); } public static final String TAG = LocationProvider.class.getSimpleName(); private final static int CONNECTION_FAILURE_RESOLUTION_REQUEST = 9000; private LocationCallback mLocationCallback; private Context mContext; private GoogleApiClient mGoogleApiClient; private LocationRequest mLocationRequest; public LocationProvider(Context context, LocationCallback callback) { mGoogleApiClient = new GoogleApiClient.Builder(context) .addConnectionCallbacks(this) .addOnConnectionFailedListener(this) .addApi(LocationServices.API) .build(); mLocationCallback = callback; // Create the LocationRequest object mLocationRequest = LocationRequest.create() .setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY) .setInterval(10 * 1000) // 10 seconds, in milliseconds .setFastestInterval(1 * 1000); // 1 second, in milliseconds mContext = context; } public void connect() { mGoogleApiClient.connect(); } public void disconnect() { if (mGoogleApiClient.isConnected()) { LocationServices.FusedLocationApi.removeLocationUpdates(mGoogleApiClient, this); mGoogleApiClient.disconnect(); } } public void locationUpdate(){ if (ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED) { ActivityCompat.requestPermissions(this, new String[]{ android.Manifest.permission.ACCESS_FINE_LOCATION }, 10); }else{ Location location = LocationServices.FusedLocationApi.getLastLocation(mGoogleApiClient); if (location == null) { LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient, mLocationRequest, this); } else { mLocationCallback.handleNewLocation(location); } } } @Override public void onConnected(Bundle bundle) { Log.i(TAG, "Location services connected."); locationUpdate(); } @Override public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) { switch (requestCode) { case 10: if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) { locationUpdate(); } return; } } @Override public void onConnectionSuspended(int i) { } @Override public void onConnectionFailed(ConnectionResult connectionResult) { /* * Google Play services can resolve some errors it detects. * If the error has a resolution, try sending an Intent to * start a Google Play services activity that can resolve * error. */ if (connectionResult.hasResolution() && mContext instanceof Activity) { try { Activity activity = (Activity)mContext; // Start an Activity that tries to resolve the error connectionResult.startResolutionForResult(activity, CONNECTION_FAILURE_RESOLUTION_REQUEST); /* * Thrown if Google Play services canceled the original * PendingIntent */ } catch (IntentSender.SendIntentException e) { // Log the error e.printStackTrace(); } } else { /* * If no resolution is available, display a dialog to the * user with the error. */ Log.i(TAG, "Location services connection failed with code " + connectionResult.getErrorCode()); } } @Override public void onLocationChanged(Location location) { mLocationCallback.handleNewLocation(location); } } 

这是错误日志：

 java.lang.NullPointerException: Attempt to invoke virtual method 'int android.content.Context.checkPermission(java.lang.String, int, int)' on a null object reference at android.content.ContextWrapper.checkPermission(ContextWrapper.java:637) at android.support.v4.content.ContextCompat.checkSelfPermission(ContextCompat.java:387) at dtt.romano.rsrpechhulp.LocationProvider.onConnected(LocationProvider.java:68) at com.google.android.gms.common.internal.zzk.zzk(Unknown Source) at com.google.android.gms.common.api.internal.zzj.zzi(Unknown Source) at com.google.android.gms.common.api.internal.zzh.zzpx(Unknown Source) at com.google.android.gms.common.api.internal.zzh.onConnected(Unknown Source) at com.google.android.gms.common.api.internal.zzl.onConnected(Unknown Source) at com.google.android.gms.common.api.internal.zzc.onConnected(Unknown Source) at com.google.android.gms.common.internal.zzj$zzg.zzqL(Unknown Source) at com.google.android.gms.common.internal.zzj$zza.zzc(Unknown Source) at com.google.android.gms.common.internal.zzj$zza.zzw(Unknown Source) at com.google.android.gms.common.internal.zzj$zzc.zzqN(Unknown Source) at com.google.android.gms.common.internal.zzj$zzb.handleMessage(Unknown Source) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:148) at android.app.ActivityThread.main(ActivityThread.java:5417) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 

Answer 1

 if (ActivityCompat.checkSelfPermission((Activity)mContext, android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED) { ActivityCompat.requestPermissions((Activity)mContext, new String[]{ android.Manifest.permission.ACCESS_FINE_LOCATION }, 10); } 

尝试使用（Activity）mContext而不是这个。 可能是它的帮助。

Answer 2

 if (ActivityCompat.checkSelfPermission(ActivityName.this, android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED) { ActivityCompat.requestPermissions(ActivityName.this, new String[]{ android.Manifest.permission.ACCESS_FINE_LOCATION }, 10); 

}

试试你的ActivityName.this