DDM 20201117

package com.joythis.android.distancebetweendates;

import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;

import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.Spinner;
import android.widget.TextView;

import java.util.ArrayList;

public class DatesRequesterActivity extends AppCompatActivity {
    AmUtil mUtil;
    Context mContext;

    AmCalendar mDate1, mDate2;

    Button mBtnRequestDate1, mBtnRequestDate2;
    TextView mTvShowDate1, mTvShowDate2;
    Button mBtnCompute;
    Spinner mSpnDates;

    ListView mLvFeedback;
    ArrayList<String> mAlComputedDistances;
    ArrayAdapter<String> mAd;

    Button.OnClickListener mButtonClickHandler = new Button.OnClickListener() {
        @Override
        public void onClick(View v) {
            int id = v.getId();
            switch(id){
                case R.id.idBtnRequestDate1:
                    actionRequestDate1();
                    break;
                case R.id.idBtnRequestDate2:
                    actionRequestDate2();
                    break;
                case R.id.idBtnCompute:
                    actionComputeDistanceBetweenDates();
                    break;
            }//switch
        }//onClick
    };//mButtonClickHandler

    public final static int
            CALL_ME_ON_THIS_NUMBER_WHEN_YOU_HAVE_DATE1 = 1234;

    //2020-11-17
    public final static int
            CALL_ME_ON_THIS_NUMBER_WHEN_YOU_HAVE_DATE2 = 4321;

    void goPickDate1(){
        Intent goToDatesInputActivityAndPickDate =
                new Intent(
                        this,
                        DateInputActivity.class
                );

        //startActivity(goToDatesInputActivityAndPickDate);

        startActivityForResult(
            goToDatesInputActivityAndPickDate,
                CALL_ME_ON_THIS_NUMBER_WHEN_YOU_HAVE_DATE1
        );
    }//goPickDate1

    void goPickDate2(){
        Intent goToDatesInputActivityAndPickDate =
                new Intent(
                        this,
                        DateInputActivity.class
                );

        //startActivity(goToDatesInputActivityAndPickDate);

        startActivityForResult(
                goToDatesInputActivityAndPickDate,
                CALL_ME_ON_THIS_NUMBER_WHEN_YOU_HAVE_DATE2
        );
    }//goPickDate2

    public final static int DEFAULT_YEAR = 2020;
    public final static int DEFAULT_MONTH = 11;
    public final static int DEFAULT_DAY = 17;

    //CTRL+O
    @Override
    protected void onActivityResult
    (int requestCode, //contact code for the result
     int resultCode, //RESULT_OK or RESULT_CANCELED
     @Nullable Intent data //contains the extras (the results) transported, sent by the called
    )
    {
        super.onActivityResult(requestCode, resultCode, data);

        boolean bUserConfirmedData = resultCode == RESULT_OK;
        boolean bUserCanceled = resultCode == RESULT_CANCELED;

        if (bUserConfirmedData){
            boolean bNotEmptyData = data!=null;
            if (bNotEmptyData){
                int y = data.getIntExtra(
                        DateInputActivity.KEY_YEAR, DEFAULT_YEAR
                );
                int m = data.getIntExtra(
                        DateInputActivity.KEY_MONTH, DEFAULT_MONTH
                );
                int d = data.getIntExtra(
                            DateInputActivity.KEY_DAY, DEFAULT_DAY
                        );

                String strDateReceived = getResources().getString(
                    R.string.strYMD,
                    y,m,d
                );

                switch(requestCode){
                    case CALL_ME_ON_THIS_NUMBER_WHEN_YOU_HAVE_DATE1:
                        this.mDate1 = new AmCalendar(y,m,d);
                        mTvShowDate1.setText(strDateReceived);
                        break;

                    case CALL_ME_ON_THIS_NUMBER_WHEN_YOU_HAVE_DATE2:
                        this.mDate2 = new AmCalendar(y,m,d);
                        mTvShowDate2.setText(strDateReceived);
                        break;
                }//switch

                /*
                if, by now, both mDate1 and mDate2 have become NOT null
                we should enable the compute button, because
                computation is now possible
                 */
                if (mDate1!=null && mDate2!=null){
                    mBtnCompute.setEnabled(true);
                }//if

           }//if there is data
        }//if user confirmed the interaction
    }//onActivityResult

    void actionRequestDate1(){
        goPickDate1();
    }//actionRequestDate1

    void actionRequestDate2(){
        goPickDate2();
    }//actionRequestDate2

    void actionComputeDistanceBetweenDates(){
        //TODO
        long iDistanceInDays =
            mDate1.distanceInDaysTo(mDate2);

        /*
        %s is %d day(s) apart from %s\n
         */
        String strComputationResult = getString(
            R.string.strDistanceBetweenDates,
            mDate1.toString(),
            iDistanceInDays,
            mDate2.toString()
        );

        mAlComputedDistances.add(
            0,
            strComputationResult
        );
        mAd.notifyDataSetChanged();
    }//actionConfirmDate

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

        init();
    }//onCreate

    void init(){
        mContext = this;
        mUtil = new AmUtil(this);

        mSpnDates = findViewById(R.id.idSpnDates);
        mBtnRequestDate1 = findViewById(R.id.idBtnRequestDate1);
        mBtnRequestDate2 = findViewById(R.id.idBtnRequestDate2);
        mTvShowDate1 = findViewById(R.id.idTvShowDate1);
        mTvShowDate2 = findViewById(R.id.idTvShowDate2);
        mBtnCompute = findViewById(R.id.idBtnCompute);
        mLvFeedback = findViewById(R.id.idLvFeedback);

        String[] aSpinnerOptions = {
            "option A", "option B"
        };
        mUtil.populateSpinner(
            mSpnDates,
            aSpinnerOptions //simplest alt
            //for those interested in improving the app, here provide options sourced from the WWW
        );

        mAlComputedDistances = new ArrayList<>();
        mAd = new ArrayAdapter<>(
            mContext,
            android.R.layout.simple_list_item_1,
            mAlComputedDistances
        );
        mLvFeedback.setAdapter(mAd);

        Button[] aBtns = {
            mBtnRequestDate1,
            mBtnRequestDate2,
            mBtnCompute
        };
        for (Button b : aBtns)
            b.setOnClickListener(mButtonClickHandler);

        //the button that requests the computation should not be usable
        //until both dates become available
        if (mDate1==null && mDate2==null){
            mBtnCompute.setEnabled(false);
        }//if
    }//init


}//DatesRequesterActivity

**

package com.joythis.android.distancebetweendates;

import android.app.Activity;
import android.widget.ArrayAdapter;
import android.widget.Spinner;

public class AmUtil {
    Activity mA;

    public AmUtil(
        Activity pA
    ){
        this.mA = pA;
    }//AmUtil

    public void populateSpinner(
        Spinner pSpn,
        String[] pOptions
    ){
        ArrayAdapter<String> ad = new ArrayAdapter<>(
            this.mA,
            android.R.layout.simple_spinner_item,
            pOptions
        );

        //optional
        ad.setDropDownViewResource(
            android.R.layout.simple_spinner_dropdown_item
        );

        pSpn.setAdapter(ad);
    }//populateSpinner
}//AmUtil

**

package com.joythis.android.distancebetweendates;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.NumberPicker;

import java.util.ArrayList;
import java.util.Calendar;

public class DateInputActivity extends AppCompatActivity {
    Context mContext;

    NumberPicker mNpYear, mNpMonth, mNpDay;
    Button mBtnConfirmDate;
    ListView mLvFeedback;

    ArrayList<String> mAlUserMsgs;
    ArrayAdapter<String> mAd;

    Button.OnClickListener mButtonClickHandler =
        new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                actionSendDateToOtherActivity();
            }//onClick
        };//mButtonClickHandler

    NumberPicker.OnValueChangeListener mNumberPickerChangeHandler =
    new NumberPicker.OnValueChangeListener() {
        @Override
        public void onValueChange(
            NumberPicker picker,
            int oldVal,
            int newVal
        ){
            int y = mNpYear.getValue();
            int m = mNpMonth.getValue();
            int d = mNpDay.getValue();
            boolean bValidDate = AmCalendar.validDay(y, m, d);

            //some of the code that follows became
            //unnecessary, because of this line
            mNpDay.setMaxValue(
                AmCalendar.daysInMonth(y,m)
            );

            if (!bValidDate){
                //%1$d-%2$d-%3$d invalid date!
                String strMsg =
                    getResources().getString(
                        R.string.strInvalidDate,
                        y,m,d
                    );

                mAlUserMsgs.add(0, strMsg);
                mAd.notifyDataSetChanged();

                //TODO
                int iMaxDaysForSelectedYM =
                    AmCalendar.daysInMonth(y, m);

                /*
<string name="strInvalidDate">%1$d-%2$d-%3$d invalid date!</string>
<string name="strDayFixed">Day fixed from %1$d to %2$d.</string>
                 */
                mNpDay.setValue(iMaxDaysForSelectedYM);
                mNpDay.setMaxValue(iMaxDaysForSelectedYM);

                strMsg = getString(
                    R.string.strDayFixed,
                    d,
                    iMaxDaysForSelectedYM
                );
                mAlUserMsgs.add(0, strMsg);
                mAd.notifyDataSetChanged();
            }//if
        }//onValueChange
    };//mNumberChangeHandler

    /*
    single purpose:
    - exemplify how to navigate from this activity to A2
     */
    public static String KEY_HELLO = "KEY_HELLO";
    public static String KEY_THE_USER_DATE = "KEY_THE_USER_DATE";
    public static String KEY_YEAR = "KEY_YEAR";
    public static String KEY_MONTH = "KEY_MONTH";
    public static String KEY_DAY = "KEY_DAY";
    public static String KEY_BUNDLE = "KEY_BUNDLE";

    void actionSendDateToOtherActivity(){
        /*
        Intent intentToRespondToDatesRequester = new Intent(
            //this,
            DateInputActivity.this, //source intance
            DatesRequesterActivity.class//class of destination
        );
         */
        Intent intentResponse = new Intent();

        int y, m, d;
        y=mNpYear.getValue();
        m=mNpMonth.getValue();
        d=mNpDay.getValue();

        intentResponse.putExtra(
            KEY_YEAR, y
        );
        intentResponse.putExtra(
            KEY_MONTH,
            m
        );
        intentResponse.putExtra(
            KEY_DAY,
            d
        );

        /*
        //we are <del>NOT</del> sending the user selected date
        startActivity(
            intentToRespondToDatesRequester
        );
         */

        setResult(
            //RESULT_CANCELED
            RESULT_OK,
            intentResponse
        );

        finish();
    }//actionSendDateToOtherActivity

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

        init();
    }//onCreate

    void init(){
        mContext = DateInputActivity.this;

        mNpYear = findViewById(R.id.idNpYear);
        mNpMonth = findViewById(R.id.idNpMonth);
        mNpDay = findViewById(R.id.idNpDay);
        mBtnConfirmDate = findViewById(R.id.idBtnConfirmDate);
        mLvFeedback = findViewById(R.id.idLvFeedback);

        NumberPicker[] aNpYMD = {
            mNpYear, mNpMonth, mNpDay
        };
        for (NumberPicker np : aNpYMD)
            np.setOnValueChangedListener(mNumberPickerChangeHandler);

        //TODO
        Calendar cal = Calendar.getInstance();
        mNpYear.setMinValue(1);
        mNpYear.setMaxValue(9999);
        mNpYear.setValue(
            //2020
            /*
            Calendar.getInstance().get(
                Calendar.YEAR
            )
             */
            cal.get(Calendar.YEAR)
        );

        mNpMonth.setMinValue(1);
        mNpMonth.setMaxValue(12);
        mNpMonth.setValue(
            //11
            /*
            Calendar.getInstance().get(
                Calendar.MONTH
            )
             */
            cal.get(
                Calendar.MONTH
            )+1
        );

        mNpDay.setMinValue(1);
        mNpDay.setMaxValue(31);
        mNpDay.setValue(
            //10
            cal.get(Calendar.DAY_OF_MONTH)
        );

        mAlUserMsgs = new ArrayList<>();
        mAd = new ArrayAdapter<>(
            mContext,
            android.R.layout.simple_list_item_1,
            mAlUserMsgs
        );
        mLvFeedback.setAdapter(mAd);

        mBtnConfirmDate.setOnClickListener(
            mButtonClickHandler
        );
    }//init
}

**

package com.joythis.android.distancebetweendates;

import java.util.Calendar;

public class AmCalendar {
    private int mYear, mMonth, mDay;
    private Calendar mCal;

    public Calendar getCalendar(){return this.mCal;}

    public AmCalendar(
        int pY,
        int pM,
        int pD
    ){
        this.mYear = pY;
        this.mMonth = pM;
        this.mDay = pD;

        //mCal that corresponds to the mYear, mMonth, mDay trio
        mCal = Calendar.getInstance();
        mCal.set(Calendar.YEAR, this.mYear);
        mCal.set(Calendar.MONTH, this.mMonth-1);
        mCal.set(Calendar.DAY_OF_MONTH, this.mDay);
    }//AmCalendar

    public long distanceInDaysTo(
        AmCalendar pSomeOtherCalendar
    ){
        long msCurrent = mCal.getTimeInMillis();
        long msOther =
            pSomeOtherCalendar.getCalendar().getTimeInMillis();

        long msDif = Math.abs(msCurrent-msOther);
        //int iDays = (int)(msDif/1000/60/60/24);
        long iDays = msDif/1000/60/60/24;
        return iDays;
    }//distanceInDaysTo

    public static boolean validYear(int pY){
        return pY>=1;
    }//validYear

    public static boolean validMonth(int pM){
        return pM>=1 && pM<=12;
    }//validMonth

    public static boolean validDay(
        int pY,
        int pM,
        int pD
    ){
        return pD>=1 && pD<=AmCalendar.daysInMonth(pY, pM);
    }//validDay

    public final static int IMPOSSIBLE_MONTH = -1;
    public static int daysInMonth (
        int pY,
        int pM
    ){
        switch(pM){
            case 1:
            case 3:
            case 5:
            case 7:
            case 8:
            case 10:
            case 12:
                return 31;
            case 4:
            case 6:
            case 9:
            case 11:
                return 30;
            case 2:
                return AmCalendar.leapYear(pY) ? 29 : 28;
            default:
                return IMPOSSIBLE_MONTH;
        }//switch
    }//daysInMonth

    public static boolean leapYear(
        int pY
    ){
        boolean bM400 = pY%400 == 0;
        boolean bM100 = pY%100 == 0;
        boolean bM4 = pY%4 == 0;

        boolean bCase1 = bM400; //2000
        boolean bCase2 = bM4 && !bM100; //1996

        return bCase1 || bCase2;
    }//leapYear

    public String toString(){
        return String.format("%d-%d-%d", mYear, mMonth, mDay);
    }//toString
}//AmCalendar

**

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

    <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.DistanceBetweenDates">
        <activity android:name=".DatesRequesterActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <activity android:name=".A2">

        </activity>

        <activity android:name=".DateInputActivity">

        </activity>
    </application>

</manifest>