Question

已解决：：“在调用getUid之前检查FirebaseAuth.getInstance（）。getCurrentUser（）！= null。” –斯里卡·雷迪（Srikar Reddy）（评论）

上下文：我的应用正在使用Firebase和Geofire来获取用户位置并进行更新。当用户不在“地图屏幕”上时，它将从Firebase数据库中删除其Geofire位置。这是一个实时跟踪应用程序。该应用程序可以正确跟踪和更新用户。一切正常。他们的Geofire数据已正确从Firebase中删除。除了，当我注销时，我遇到了问题。重新登录也可以。

问题：当我注销时，应用程序因以下错误而崩溃：

java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.google.firebase.auth.FirebaseUser.getUid()' on a null object reference

我尝试过的事情：

  String vendorId = Objects.requireNonNull(FirebaseAuth.getInstance().getCurrentUser()).getUid();

但是它也因以下错误而崩溃：

 java.lang.RuntimeException: Unable to stop activity {com.example.zzyzj.eloteroman/com.example.zzyzj.eloteroman.VendorMapsActivity}: java.lang.NullPointerException

我的代码：

 //Logout Menu Option Button
@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {

        // If Logout Button is clicked within 2 Seconds log user out
        case R.id.logoutMenuOption:
            if (logoutAppPressAgain + 2000 > System.currentTimeMillis()) {
                logoutToast.cancel();

                // Remove VendorOnline Child before logging out to prevent crash
                removeVendorOnline();

                FirebaseAuth.getInstance().signOut();
                Intent logoutIntent = new Intent(VendorMapsActivity.this, WelcomeActivity.class);
                startActivity(logoutIntent);
                finish();
            } else {
                logoutToast = Toast.makeText(getBaseContext(), R.string.press_button_again_to_logout, Toast.LENGTH_SHORT);
                logoutToast.show();
            }

            logoutAppPressAgain = System.currentTimeMillis();
    }

    return super.onOptionsItemSelected(item);
}

 @Override
public void onLocationChanged(Location location) {

    lastLocation = location;

    if (currentUserLocationMarker != null) {
        currentUserLocationMarker.remove();
    }

    LatLng latLng = new LatLng(location.getLatitude(), location.getLongitude());

    MarkerOptions markerOptions = new MarkerOptions();
    markerOptions.position(latLng);
    markerOptions.title(getString(R.string.user_current_location_marker_title));
    markerOptions.icon(BitmapDescriptorFactory.fromResource(R.drawable.corn_icon));

    currentUserLocationMarker = mMap.addMarker(markerOptions);

    float zoom = 17.0f;

    mMap.setMapType(GoogleMap.MAP_TYPE_NORMAL);
    mMap.getUiSettings().setZoomControlsEnabled(true);
    mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(latLng, zoom));
    mMap.getUiSettings().setRotateGesturesEnabled(false);
    mMap.getUiSettings().setZoomControlsEnabled(false);

    // Adds VendorOnline Child to Firebase when Vendor is On This Activity
    addVendorOnline();

}

 @Override
protected void onStart() {
    super.onStart();
    if (googleApiClient != null) {
        googleApiClient.connect();
    }
}

@Override
protected void onStop() {
    super.onStop();

    // When Vendor is not on this screen activity it will remove their data from Firebase
    removeVendorOnline();

    if (googleApiClient.isConnected()) {
        googleApiClient.disconnect();
    }
}

// When user swipe closes app it logs them out

@Override
protected void onDestroy() {
    super.onDestroy();
    removeVendorOnline();
    FirebaseAuth.getInstance().signOut();
}

// Prevent user from going to unwanted Activities when back button is pressed, instead user logout

@Override
public void onBackPressed() {
    if (exitAppPressBack + 2000 > System.currentTimeMillis()) {
        exitAppBackToast.cancel();
        super.onBackPressed();

        // Remove VendorOnline Child before logging out to prevent crash
        removeVendorOnline();

        FirebaseAuth.getInstance().signOut();
        Intent logoutIntent = new Intent(VendorMapsActivity.this, WelcomeActivity.class);
        startActivity(logoutIntent);
        finish();
    } else {
        exitAppBackToast = Toast.makeText(getBaseContext(), R.string.press_back_one_more_time_to_exit, Toast.LENGTH_SHORT);
        exitAppBackToast.show();
    }

    exitAppPressBack = System.currentTimeMillis();
}


 // Code to store Vendor data when a Vendor is Online in Firebase
// Creates new Child within Firebase Database "VendorsOnline" when a Vendor is Online
// Uses Geofire to update location and update Vendor Online Data in Firebase

public void addVendorOnline(){

    String vendorId = FirebaseAuth.getInstance().getCurrentUser().getUid();
    DatabaseReference vendorIdReference = FirebaseDatabase.getInstance().getReference("VendorOnline");
    GeoFire vendorGeoFire = new GeoFire(vendorIdReference);
    vendorGeoFire.setLocation(vendorId, new GeoLocation(lastLocation.getLatitude(), lastLocation.getLongitude()));
}

// Removes Vendor from VendorOnline Child in Firebase

public void removeVendorOnline() {

    String vendorId = FirebaseAuth.getInstance().getCurrentUser().getUid();
    DatabaseReference vendorIdReference = FirebaseDatabase.getInstance().getReference("VendorOnline");
    GeoFire vendorGeoFire = new GeoFire(vendorIdReference);
    vendorGeoFire.removeLocation(vendorId);
}

当用户在使用Geofire时使用Firebase注销时，应用程序崩溃

0 个答案: