TreeHouse: Making our code asynchronous

Networking Asynchronous Get
update

//Call back method = basically telling OkHttp to call us back when it is done with its work.
// Enqueue() method = We are telling OkHttp to call us back
// when OkHttp Library is done it calls us back with the:
// onResponse() method
// and if there is an error
// onFailure() method
// see image explanation:

package com.teamtreehouse.stormy;

import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;

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 java.io.IOException;


public class MainActivity extends ActionBarActivity {

    public static final String TAG= MainActivity.class.getSimpleName();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        String apiKey = "d5faf0cb201f103df4dde0b8b0a4f490";
        double latitude = 37.8267;
        double longitude = -122.423;
        String forecastUrl = "https://api.forecast.io/forecast/d5faf0cb201f103df4dde0b8b0a4f490/," + apiKey +
                "/" + latitude +"/" + "," + longitude;

        OkHttpClient client = new OkHttpClient();
        Request request = new Request.Builder().url(forecastUrl).build();


        Call call = client.newCall(request);
        call.enqueue(new Callback() { // the enqueue method here executes the call, but it does so by putting it in a queue. It doesn't execute it right away, immediately. OkHttp has a queue that will execute asynchronous calls in the order they are added to the queue and it executes in the background. Simple.

            // This should be somewhat familiar at this point, once again we have an anonymous inner class.
            // It's a callback type, and it has two methods that we need to override: on Failure and on Response.
            @Override
            public void onFailure(Request request, IOException e) {

            }

            @Override
            public void onResponse(Response response) throws IOException {
                try {
                    // Response response = call.execute(); <-execute is a synchronous method so we delete this line
                    if (response.isSuccessful()){
                        Log.v(TAG, response.body().string());
                    }
                } catch (IOException e) {
                    Log.e(TAG, "Exception caught: ", e);
                }

            }
        });

        Log.d(TAG, "Main UI code is running!"); // log that code is running so we can tell it is running. simple.
    }
}




//----------------------------------------------------------------------------------------------
AndroidManifest.xml

// We haven't really talked about permissions yet.
// But whenever we're doing something out of the ordinary in an Android app,
// even connecting to the internet, we need to request special permission.
// We do this in the Android manifest.

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.teamtreehouse.stormy" >

    <!--add this. It solves the 'java.lang.Security Exception: Permission denied (missing INTERNET permission)' by requesting permission to use the internet -->
    <uses-permission android:name="android.permission.INTERNET" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>
//----------------------------------------------------------------------------------------------

// http://developer.android.com/guide/topics/security/permissions.html#permissions
// https://teamtreehouse.com/library/build-a-weather-app/concurrency-and-error-handling/making-our-code-asynchronous