DDM 2020-11-19

package com.joythis.android.minimalhttps;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Context;
import android.os.AsyncTask;
import android.os.Bundle;
import android.widget.TextView;

import javax.net.ssl.HttpsURLConnection;

public class MainActivity extends AppCompatActivity {

    class MyAsyncTask extends AsyncTask
    <
    String//input data type (URL)
    ,
    Void //progress data type
    ,
    String //result data type (remote content)
    >
    {
        String mStrRemoteContent;

        //CTRL+O Override
        /*
        automatically called by the Android framework
        immediately before starting the execution of the task
        coded in doInBackground
         */
        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            mStrRemoteContent = "";
            mTvRemoteContent.setText("Loading...");
        }//onPreExecute

        /*
        here is where we should write the code
        that will run on its own thread
        and asynchronously
         */
        @Override
        protected String doInBackground(
            String... strings //variable number of args of String datatype
        )
        {
            String strUrl = strings[0];

            mStrRemoteContent = "";
            /*
            mStrRemoteContent = AmHttp.consumeHttpsAtUrl(
                strUrl
            );
             */
            mStrRemoteContent = AmHttp.consumeHttpAtUrl(
                    strUrl
            );

            //raw consumption until this point

            //return null;
            return mStrRemoteContent;
        }//doInBackground

        /*
        automatically called when
        doInBackground completes
         */
        @Override
        protected void onPostExecute(String s) {
            super.onPostExecute(s);

            /*
            the remote content has been loaded
            and will now be displayed in the TextView
             */

            /*
            opportunity to process the raw data
             */
            String strProcessingResult = processRawData(s);

            //mTvRemoteContent.setText(s);
            mTvRemoteContent.setText(strProcessingResult);
        }//onPostExecute
    }//MyAsyncTask

    private String processRawData(String pStrRawData){
        String strProcessingResult = "";

        String[] aRecordContactsFromRawData =
            pStrRawData.split("\n");

        for (String strContact : aRecordContactsFromRawData){
            String[] aParts = strContact.split("\t");
            String strContactName = aParts[0];
            String strContactAddress = aParts[1];

            strProcessingResult+=
                String.format(
                    "Name: %s ; Address: %s\n",
                    strContactName,
                    strContactAddress
                );
        }//for

        return strProcessingResult;
    }//processRawData

    public static final String SOURCE_HTTPS =
        "https://arturmarques.com/edu/contacts.TSV";

    public static final String SOURCE_HTTP =
        "http://arturmarques.com/edu/contacts.TSV";

    Context mContext;
    TextView mTvRemoteContent;

    MyAsyncTask mAsyncTaskThatReadsTheRemoteContent;

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

        init();
    }//onCreate

    void approach1(){
        /*
        we can NOT consume external resources
        in the same thread that handles the user interface!
        There is the risk that these resources take too long
        to become available: during that time the user interface
        would be unresponsive (A.N.R.), which is not acceptable.

        We must do it in a different thread
        We must do it asynchronously
         */

        //E/@AmHttp: android.os.NetworkOnMainThreadException
        mTvRemoteContent.setText(
                AmHttp.consumeHttpsAtUrl(
                        SOURCE_HTTPS
                )
        );
    }//approach1

    /*
    will consume in its own thread
    will consume asynchronously
     */
    void approach2(){
        /*
        use MyAsyncTask via mAsyncTaskThatReadsTheRemoteContent
         */
        mAsyncTaskThatReadsTheRemoteContent.execute(
            SOURCE_HTTPS
        );
    }//approach2

    void init(){
        mContext = this;
        mTvRemoteContent = findViewById(R.id.idTvRemoteContent);
        mAsyncTaskThatReadsTheRemoteContent =
            new MyAsyncTask();

        //approach1(); //FAIL!

        approach2(); //OK!
    }//init
}

//**

package com.joythis.android.minimalhttps;

import android.util.Log;

import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.nio.charset.StandardCharsets;

import javax.net.ssl.HttpsURLConnection;

public class AmHttp {
    public final static String TAG = "@AmHttp";
    public static final int END_OF_CONTENT = -1;

    public static String consumeHttpsAtUrl(
        String pUrl
    ){
        String strRemoteContent = "";

        try{
           URL url = new URL(pUrl);
           HttpsURLConnection httpsCon =
               (HttpsURLConnection)
               url.openConnection();

           if(httpsCon!=null){
               InputStream is =
                   httpsCon.getInputStream();

               //assures the correct consumption of UTF8 symbols in the stream
               InputStreamReader isr =
                   new InputStreamReader(
                       is,
                       StandardCharsets.UTF_8
                   );

               char c; int iByte;
               while((iByte=isr.read())!=END_OF_CONTENT){
                   c = (char)iByte;
                   strRemoteContent += c;
               }//while

               isr.close();
               is.close();
               return strRemoteContent;
           }
        }//try
        catch (Exception e){
            String strMsg = e.toString();
            Log.e(
                TAG//stamp
                ,
                strMsg
            );
        }//catch

        return strRemoteContent;
    }//consumeHttpsAtUrl

    public static String consumeHttpAtUrl(
        String pUrl
    ){
        String strRemoteContent = "";

        try{
            URL url = new URL(pUrl);
            HttpURLConnection httpCon =
                (HttpURLConnection)
                url.openConnection();

            if(httpCon!=null){
                InputStream is = httpCon.getInputStream();

                //assures the correct consumption of UTF8 symbols in the stream
                InputStreamReader isr =
                        new InputStreamReader(
                            is,
                            StandardCharsets.UTF_8
                        );

                char c; int iByte;
                while((iByte=isr.read())!=END_OF_CONTENT){
                    c = (char)iByte;
                    strRemoteContent += c;
                }//while

                isr.close();
                is.close();
                return strRemoteContent;
            }//if
        }//try
        catch (Exception e){
            String strMsg = e.toString();
            Log.e(
                    TAG//stamp
                    ,
                    strMsg
            );
        }//catch

        return strRemoteContent;
    }//consumeHttpAtUrl
}//AmHttp

//**

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/idTvRemoteContent"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

//**

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

    <!-- non-dangerous permission -->
    <uses-permission android:name="android.permission.INTERNET"></uses-permission>

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

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

</manifest>