Example implemented

Retrofit-Library-Tutorial-master.iml

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+<?xml version="1.0" encoding="UTF-8"?>
+<module external.system.id="GRADLE" type="JAVA_MODULE" version="4">
+  <component name="FacetManager">
+    <facet type="android-gradle" name="Android-Gradle">
+      <configuration>
+        <option name="GRADLE_PROJECT_PATH" value=":" />
+      </configuration>
+    </facet>
+    <facet type="android" name="Android">
+      <configuration>
+        <option name="ALLOW_USER_CONFIGURATION" value="false" />
+      </configuration>
+    </facet>
+  </component>
+  <component name="NewModuleRootManager" inherit-compiler-output="true">
+    <exclude-output />
+    <content url="file://$MODULE_DIR$" />
+    <orderEntry type="sourceFolder" forTests="false" />
+  </component>
+</module>

app/build.gradle

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+apply plugin: 'com.android.application'
+
+android {
+    compileSdkVersion 23
+    buildToolsVersion "24.0.0 rc3"
+
+    defaultConfig {
+        applicationId "com.android.gifts.retrofit"
+        minSdkVersion 14
+        targetSdkVersion 23
+        versionCode 1
+        versionName "1.0"
+    }
+    buildTypes {
+        release {
+            minifyEnabled false
+            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
+        }
+    }
+}
+
+dependencies {
+    compile fileTree(dir: 'libs', include: ['*.jar'])
+    testCompile 'junit:junit:4.12'
+    compile 'com.android.support:appcompat-v7:23.3.0'
+    compile 'com.squareup.retrofit2:retrofit:2.0.2'
+    compile 'com.squareup.retrofit2:converter-gson:2.0.2'
+}

app/proguard-rules.pro

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+# Add project specific ProGuard rules here.
+# By default, the flags in this file are appended to flags specified
+# in /Users/ahmedadel/Downloads/adt-bundle-mac-x86_64-20140702/sdk/tools/proguard/proguard-android.txt
+# You can edit the include path and order by changing the proguardFiles
+# directive in build.gradle.
+#
+# For more details, see
+#   http://developer.android.com/guide/developing/tools/proguard.html
+
+# Add any project specific keep options here:
+
+# If your project uses WebView with JS, uncomment the following
+# and specify the fully qualified class name to the JavaScript interface
+# class:
+#-keepclassmembers class fqcn.of.javascript.interface.for.webview {
+#   public *;
+#}

app/src/androidTest/java/com/android/gifts/retrofit/ApplicationTest.java

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+package com.android.gifts.retrofit;
+
+import android.app.Application;
+import android.test.ApplicationTestCase;
+
+/**
+ * <a href="http://d.android.com/tools/testing/testing_android.html">Testing Fundamentals</a>
+ */
+public class ApplicationTest extends ApplicationTestCase<Application> {
+    public ApplicationTest() {
+        super(Application.class);
+    }
+}

app/src/main/AndroidManifest.xml

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+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="com.android.gifts.retrofit">
+
+    <uses-permission android:name="android.permission.INTERNET"/>
+
+    <application
+        android:allowBackup="true"
+        android:icon="@mipmap/ic_launcher"
+        android:label="@string/app_name"
+        android:supportsRtl="true"
+        android:theme="@style/AppTheme">
+        <activity android:name=".RetrofitMainActivity">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+        </activity>
+    </application>
+
+</manifest>

app/src/main/java/com/android/gifts/retrofit/GetWeatherApi.java

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+package com.android.gifts.retrofit;
+
+import retrofit2.Call;
+import retrofit2.http.GET;
+import retrofit2.http.Query;
+
+/**
+ * Created by ahmedadel on 26/04/16.
+ */
+public interface GetWeatherApi {
+
+    /**
+     * Synchronous and Asynchronous background requests through Retrofit
+     * In regard to service interface declaration in Retrofit 1.9, you have to to declare a synchronous function,
+     * and an asynchronous separately, But on Retrofit 2.0,
+     * it is far more simple since you can declare with only just a single pattern.
+     * @param cityName London as an example
+     * @param units metrics as an example
+     * @param appId that the developer got from OpenWeatherMap after singing up
+     * @return
+     */
+    @GET("/data/2.5/weather")
+    Call<WeatherDataBean> getWeatherFromApiSyncAndAsync(
+            @Query("q") String cityName,
+            @Query("units") String units,
+            @Query("APPID") String appId);
+
+}

app/src/main/java/com/android/gifts/retrofit/RetrofitMainActivity.java

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+package com.android.gifts.retrofit;
+
+import android.os.AsyncTask;
+import android.os.Bundle;
+import android.support.v7.app.AppCompatActivity;
+import android.view.View;
+import android.widget.Button;
+import android.widget.LinearLayout;
+import android.widget.ProgressBar;
+import android.widget.TextView;
+import android.widget.Toast;
+
+import java.io.IOException;
+
+import retrofit2.Call;
+import retrofit2.Callback;
+import retrofit2.Response;
+import retrofit2.Retrofit;
+import retrofit2.converter.gson.GsonConverterFactory;
+
+public class RetrofitMainActivity extends AppCompatActivity implements View.OnClickListener {
+
+    /**
+     * Define the root OpenWeatherMap URL and your OpenWeatherMap AppID
+     */
+    private static final String API_URL = "http://api.openweathermap.org";
+    private static final String CITY_NAME = "London";
+    private static final String UNITS = "metric";
+    private static final String APP_ID = "c6afdab60aa89481e297e0a4f19af055";
+
+    /**
+     * Instance variables to represent the "London Current Weather Synchronously"
+     * and "London Current Weather Asynchronously" buttons,
+     * "Temperature", "Pressure" and "Humidity" TextViews and loadingProgressbar
+     */
+    private Button getLondonCurrentWeatherSync, getLondonCurrentWeatherAsync;
+    private TextView temperatureTextView, pressureTextView, humidityTextView;
+    private ProgressBar loadingProgressBar;
+    private LinearLayout getLondonCurrentWeatherLinearLayout;
+
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        setContentView(R.layout.activity_retrofit_main);
+
+        /**
+         * Instantiate the variables we declared above using the ID values
+         * we specified in the layout XML file.
+         */
+        getLondonCurrentWeatherSync = (Button) findViewById(R.id.activity_retrofit_main_get_weather_sync_btn);
+        getLondonCurrentWeatherAsync = (Button) findViewById(R.id.activity_retrofit_main_get_weather_async_btn);
+        getLondonCurrentWeatherLinearLayout = (LinearLayout) findViewById(R.id.activity_retrofit_main_root_ll);
+        temperatureTextView = (TextView) findViewById(R.id.activity_retrofit_main_temperature_tv);
+        pressureTextView = (TextView) findViewById(R.id.activity_retrofit_main_pressure_tv);
+        humidityTextView = (TextView) findViewById(R.id.activity_retrofit_main_humidity_tv);
+        loadingProgressBar = (ProgressBar) findViewById(R.id.activity_retrofit_main_pb);
+
+        /**
+         * Add a listener to getLondonCurrentWeatherSync and getLondonCurrentWeatherAsync so that we can handle presses
+         */
+        getLondonCurrentWeatherSync.setOnClickListener(this);
+        getLondonCurrentWeatherAsync.setOnClickListener(this);
+
+    }
+
+    @Override
+    public void onClick(View view) {
+        switch (view.getId()) {
+            /**
+             * make a synchronous background request
+             */
+            case R.id.activity_retrofit_main_get_weather_sync_btn:
+                getWeatherSync();
+                break;
+            /**
+             * make an Asynchronous background request
+             */
+            case R.id.activity_retrofit_main_get_weather_async_btn:
+                getWeatherAsync();
+                break;
+        }
+    }
+
+    /**
+     * getWeatherAsync() method will make an asynchronous background request
+     * by using Call Interface built in Retrofit Library
+     */
+    private void getWeatherAsync() {
+        getLondonCurrentWeatherLinearLayout.setVisibility(View.INVISIBLE);
+        loadingProgressBar.setVisibility(View.VISIBLE);
+        /**
+         * To make REST API call through Android Retrofit Library we may first need to build an instance of Retrofit class.
+         * This class is the main class of Retrofit Library which executes all the requests.
+         */
+        Retrofit retrofit = new Retrofit.Builder()
+                .baseUrl(API_URL)
+                .addConverterFactory(GsonConverterFactory.create())
+                .build();
+        /**
+         * Next you need to create an instance of your Interface GetWeatherApi.
+         * since create() method that is inside retrofit object return the parsed response in
+         * GetWeatherApi Interface format
+         */
+        GetWeatherApi getWeatherApi = retrofit.create(GetWeatherApi.class);
+        /**
+         * After this, call getWeatherFromApiSyncAndAsync() method from getWeatherApi object that return an instance of
+         * Call Retrofit Interface then call enqueue() method to make an asynchronous API request, and implement inside it
+         * the CallBack Interface Listener "Observer" since this Callback Interface has to methods onResponse()
+         * that is fire once a successive response is returned from OpenWeatherMap API and onFailure()
+         * that is fire once an error occurs
+         */
+        Call<WeatherDataBean> call = getWeatherApi.getWeatherFromApiSyncAndAsync(CITY_NAME, UNITS, APP_ID);
+        call.enqueue(new Callback<WeatherDataBean>() {
+            @Override
+            public void onResponse(Call<WeatherDataBean> call, Response<WeatherDataBean> response) {
+                updateUI(response.body());
+            }
+
+            @Override
+            public void onFailure(Call<WeatherDataBean> call, Throwable t) {
+                loadingProgressBar.setVisibility(View.GONE);
+                Toast.makeText(RetrofitMainActivity.this, t.getMessage(), Toast.LENGTH_SHORT).show();
+            }
+        });
+    }
+
+    /**
+     * updateUI() method will be used once a successive response is returned from OpenWeatherMap API
+     *
+     * @param weatherDataBean
+     */
+    private void updateUI(WeatherDataBean weatherDataBean) {
+        loadingProgressBar.setVisibility(View.GONE);
+        if (weatherDataBean != null) {
+            getLondonCurrentWeatherLinearLayout.setVisibility(View.VISIBLE);
+            temperatureTextView.setText("Temperature : " + weatherDataBean.getMain().getTemp() + " Celsius");
+            pressureTextView.setText("Pressure : " + weatherDataBean.getMain().getPressure());
+            humidityTextView.setText("Humidity : " + weatherDataBean.getMain().getHumidity());
+        }
+    }
+
+    /**
+     * getWeatherSync() method will make an synchronous background request
+     * by using Call Interface built in Retrofit Library
+     */
+    private void getWeatherSync() {
+        GetWeatherSync getWeatherSync = new GetWeatherSync();
+        getWeatherSync.execute();
+    }
+
+    private class GetWeatherSync extends AsyncTask<Void, Void, WeatherDataBean> {
+
+        Retrofit retrofit;
+
+        @Override
+        protected void onPreExecute() {
+            getLondonCurrentWeatherLinearLayout.setVisibility(View.INVISIBLE);
+            loadingProgressBar.setVisibility(View.VISIBLE);
+            /**
+             * To make REST API call through Android Retrofit Library we may first need to build an instance of Retrofit class.
+             * This class is the main class of Retrofit Library which executes all the requests.
+             */
+            retrofit = new Retrofit.Builder()
+                    .baseUrl(API_URL)
+                    .addConverterFactory(GsonConverterFactory.create())
+                    .build();
+        }
+
+        @Override
+        protected WeatherDataBean doInBackground(Void... params) {
+            WeatherDataBean weatherDataBean = null;
+            try {
+                /**
+                 * Next you need to create an instance of your Interface GetWeatherApi.
+                 * since create() method that is inside retrofit object return the parsed response in
+                 * GetWeatherApi Interface format
+                 */
+                GetWeatherApi getWeatherApi = retrofit.create(GetWeatherApi.class);
+                /**
+                 * After this, call getWeatherFromApiSyncAndAsync() method from getWeatherApi object that return an instance of
+                 * Call Interface and then call execute() method since this method make a request synchronous
+                 * so it needs to be handled in background thread like AsyncTask Class to avoid
+                 * NetworkOnMainThreadException runtime error.
+                 */
+                Call<WeatherDataBean> call = getWeatherApi.getWeatherFromApiSyncAndAsync(CITY_NAME, UNITS, APP_ID);
+                Response<WeatherDataBean> response = call.execute();
+                weatherDataBean = response.body();
+            } catch (final IOException e) {
+                runOnUiThread(new Runnable() {
+                    @Override
+                    public void run() {
+                        loadingProgressBar.setVisibility(View.GONE);
+                        Toast.makeText(RetrofitMainActivity.this, e.getMessage(), Toast.LENGTH_SHORT).show();
+                    }
+                });
+            }
+
+            return weatherDataBean;
+        }
+
+        /**
+         * Get the returned object from doInBackground() method and get from this object the
+         * necessary data that we want.
+         *
+         * @param weatherDataBean is the returned object that came from doInBackground() merhod
+         */
+        @Override
+        protected void onPostExecute(WeatherDataBean weatherDataBean) {
+            updateUI(weatherDataBean);
+        }
+    }
+}

app/src/main/java/com/android/gifts/retrofit/WeatherDataBean.java

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+package com.android.gifts.retrofit;
+
+/**
+ * Created by ahmedadel on 26/04/16.
+ */
+public class WeatherDataBean {
+
+    private Main main;
+
+    public Main getMain() {
+        return main;
+    }
+
+    public void setMain(Main main) {
+        this.main = main;
+    }
+
+    class Main {
+        double temp;
+        double pressure;
+        int humidity;
+
+        public double getTemp() {
+            return temp;
+        }
+
+        public void setTemp(double temp) {
+            this.temp = temp;
+        }
+
+        public double getPressure() {
+            return pressure;
+        }
+
+        public void setPressure(double pressure) {
+            this.pressure = pressure;
+        }
+
+        public int getHumidity() {
+            return humidity;
+        }
+
+        public void setHumidity(int humidity) {
+            this.humidity = humidity;
+        }
+    }
+}