Null pointer exception in java

package com.example.hemanth.stromy;

import android.app.AlertDialog;
import android.app.DownloadManager;
import android.content.Context;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;

import com.squareup.okhttp.Call;
import com.squareup.okhttp.Callback;
import com.squareup.okhttp.OkHttpClient;
import com.squareup.okhttp.Request;
import com.squareup.okhttp.Response;

import org.json.JSONException;
import org.json.JSONObject;

import java.io.IOException;

import butterknife.InjectView;


public class MainActivity extends ActionBarActivity {

   private CurrentWeather mcurrentweather;
   public static final String TAG = MainActivity.class.getSimpleName();
    @InjectView(R.id.temperatureLabel)TextView mTemperatureLabel;
    @InjectView(R.id.humidityValue) TextView mHumiditylable;
    @InjectView(R.id.precipValue) TextView mPreciplable;
    @InjectView(R.id.summaryLabel) TextView mSummaryLabel;
    @InjectView(R.id.timelabel)TextView mTimeLabel;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        String apiKey = "2b345aa7cb761cc607bce49e23e4cb72";
        double latitude = 37.8267;
        double longitude = -122.423;
        String apiUrl = "https://api.forecast.io/forecast/"+apiKey+"/"+latitude+","+longitude;
        if(isNetworkAvailable()) {
            OkHttpClient Client = new OkHttpClient();
            Request request = new Request.Builder().url(apiUrl).build();
            Call call = Client.newCall(request);
            call.enqueue(new Callback() {
                @Override
                public void onFailure(Request request, IOException e) {
                    Toast.makeText(MainActivity.this,"There are network problems",Toast.LENGTH_LONG);
                }

                @Override
                public void onResponse(Response response) {

                    try {

                        String jasonData = response.body().string();
                        if (response.isSuccessful()) {
                            Log.v(TAG,jasonData);
                            mcurrentweather = getCurrentDetails(jasonData);
                            runOnUiThread(new Runnable() {
                                @Override
                                public void run() {
                                    updateDisplay();
                                }
                            });


                        } else {
                            alertUser();
                        }
                    }
                    catch (IOException e) {
                        Log.e(TAG, "expection is ", e);
                    }
                    catch (JSONException e){
                        Log.e(TAG, "expection is ", e);
                    }
                }
            });
        }
        else{
            Toast.makeText(this,"The network is unavailable",Toast.LENGTH_LONG).show();
        }
    }

    private void updateDisplay() {
        mTemperatureLabel.setText(mcurrentweather.getmTemeperature()+"");
        mTimeLabel.setText("At "+mcurrentweather.getFormattedString()+" it will be ");
        mHumiditylable.setText(mcurrentweather.getmHumidity()+"");
        mPreciplable.setText(mcurrentweather.getmPrecipChance() + "");
        mSummaryLabel.setText(mcurrentweather.getmSummary());



    }

    private CurrentWeather getCurrentDetails(String jasonData) throws JSONException{
        JSONObject forecast = new JSONObject(jasonData);
        String timezone = forecast.getString("timezone");
        JSONObject current = forecast.getJSONObject("currently");
        CurrentWeather currentWeather = new CurrentWeather();
        currentWeather.setmHumidity(current.getDouble("humidity"));
        currentWeather.setmTemeperature(current.getDouble("temperature"));
        currentWeather.setmTimeZone(timezone);
        currentWeather.setMtime(current.getInt("time"));
        Log.i(TAG,"From Json : "+timezone);

        return currentWeather;
    }

    private boolean isNetworkAvailable() {
        ConnectivityManager manager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo networkInfo = manager.getActiveNetworkInfo();
        boolean isAvailable = false;
        if(networkInfo != null && networkInfo.isConnected()){
            isAvailable = true;
        }
        return isAvailable;
    }

    private void alertUser() {
        AlertDialogFragment dialog = new AlertDialogFragment();
        dialog.show(getFragmentManager(),"Error_dialog");

    }


}