PDM2 20201117

package com.joythis.android.ex20201117;

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 AmHttpIO {
    public final static int END_OF_CONTENTS = -1;

    String mContentsRead = "";

    public String consumeHttpsUrl(
        String pUrl
    ){
        int iBytesRead = 0;
        String strContents = "";

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

            InputStream is = httpsCon.getInputStream();

            if (is!=null){
                InputStreamReader isr = new InputStreamReader(
                        is,
                        StandardCharsets.UTF_8
                );
                if (isr!=null){
                    char c; int iByte;

                    while((iByte=isr.read())!=END_OF_CONTENTS){
                        c = (char)iByte;
                        strContents+=c;
                    }//while
                    isr.close();
                    is.close();
                    iBytesRead = strContents.length();

                    //mContentsRead = strContents;
                    //return iBytesRead;
                    return strContents;
                }//if the InputStreamReader object is non null
                else{
                    throw new Exception(
                        "null InputStreamReader!"
                    );
                }
            }//if the InputStream object is non null
            else{
                throw new Exception(
                   "null InputStream!"
                );
            }//else
        }//try
        catch (Exception e){
            Log.e(
               this.getClass().getName(),
               e.toString()
            );
        }//catch

        //return iBytesRead;
        return strContents;
    }//consumeHttpsUrl

    public String consumeHttpUrl(
        String pUrl
    ){
        int iBytesRead = 0;
        String strContents = "";

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

            InputStream is = httpsCon.getInputStream();

            if (is!=null){
                InputStreamReader isr = new InputStreamReader(
                        is,
                        StandardCharsets.UTF_8
                );
                if (isr!=null){
                    char c; int iByte;

                    while((iByte=isr.read())!=END_OF_CONTENTS){
                        c = (char)iByte;
                        strContents+=c;
                    }//while
                    isr.close();
                    is.close();
                    iBytesRead = strContents.length();

                    //mContentsRead = strContents;
                    //return iBytesRead;
                    return strContents;
                }//if the InputStreamReader object is non null
                else{
                    throw new Exception(
                            "null InputStreamReader!"
                    );
                }
            }//if the InputStream object is non null
            else{
                throw new Exception(
                        "null InputStream!"
                );
            }//else
        }//try
        catch (Exception e){
            Log.e(
                    this.getClass().getName(),
                    e.toString()
            );
        }//catch

        //return iBytesRead;
        return strContents;
    }//consumeHttpUrl

    public String getLastContentRead(){
        return this.mContentsRead;
    }
}//AmHttpIO


//**

package com.joythis.android.ex20201117;

import androidx.appcompat.app.AppCompatActivity;

import android.os.AsyncTask;
import android.os.Bundle;
import android.widget.TextView;
import android.widget.Toast;

public class DisplayHttpContentActivity extends AppCompatActivity {

    class LoadAndDisplayAsynchronously
    extends AsyncTask
    <
    String, //URL / data type of the input data (compatible with doinbackground)
    Void, //data type for the progress indicator (Void if none)
    String //contents read / data type for the result of entire background execution
    >
    {
        /*
        automatically called by the framework just before it calls "doinbackground"
         */
        @Override
        protected void onPreExecute() {
            super.onPreExecute();

            mTvFeedback.setText("Started loading...");
        }//onPreExecute

        @Override
        protected String doInBackground(String... strings) {
            String strUrl = strings[0];

            String strContentRead = mHttpIO.consumeHttpsUrl(strUrl);
            //return null;
            return strContentRead;
        }//doInBackground

        /*
        will be automatically called by the framework when "doinbackground" ends
         */
        @Override
        protected void onPostExecute(String s) {
            super.onPostExecute(s);

            //process the data!
            //extracting and parsing
            //extraction
            String[] aRecords = s.split("\n");

            //parsing
            String strProcessed = "";
            for (String strRecord : aRecords){
                String[] aParts = strRecord.split("\t");
                String strDate = aParts[0];
                String strDescription = aParts[1];

                strProcessed+="Date: "+strDate+"[ "+ strDescription + " ]\n";
            }//for

            //mTvFeedback.setText(s);
            mTvFeedback.setText(strProcessed);
        }//onPostExecute
    }//LoadAndDisplayAsynchronously

    TextView mTvFeedback;

    AmHttpIO mHttpIO;

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

        init();
    }//onCreate

    public final static String TEST_URL =
        "https://arturmarques.com/edu/pdm2/dates.TSV";

    void init(){
        mHttpIO = new AmHttpIO();

        mTvFeedback = findViewById(R.id.idTvFeedback);

        /*
        valid algorithm that Android refuses to execute
        because
        "NetworkOnMainThreadException"
        solution: execute it asynchronously
         */

        try {
            loadAndDisplay(
                    TEST_URL,
                    mTvFeedback
            );
        }//try
        catch(Exception e){
            Toast t = Toast.makeText(
                this,
                e.toString(),
                Toast.LENGTH_LONG
                );
            t.show();
        }//catch

        loadAndDisplay2();
    }//init

    void loadAndDisplay(
        String pUrl,
        TextView pTvWhereToDisplayTheLoadedContents
    ){
        /*
        mHttpIO.consumeHttpsUrl(pUrl);
        String strContents = mHttpIO.getLastContentRead();
         */
        String strContents = mHttpIO.consumeHttpUrl(pUrl);
        //String strContents = mHttpIO.consumeHttpsUrl(pUrl);
        pTvWhereToDisplayTheLoadedContents.setText(strContents);
    }//loadAndDisplay

    void loadAndDisplay2(){
        LoadAndDisplayAsynchronously taskToConsumeHttpsAsynchronously =
            new LoadAndDisplayAsynchronously();

        taskToConsumeHttpsAsynchronously.execute(TEST_URL);
    }//loadAndDisplay2

}//DisplayHttpContentActivity