package com.codedocu.test02;

import android.graphics.Color;
import android.graphics.drawable.Drawable;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Gravity;
import android.view.View;
import android.widget.CheckBox;
import android.widget.TableLayout;
import android.widget.TableRow;
import android.widget.TextView;

import java.sql.Time;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;


public class MainActivity extends AppCompatActivity {

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

    public void btnStart_onClick(View view) {
        create_Table();
    }

    public void create_Table(){
        //-------< create_Table() >--------
        TableLayout tbl=findViewById(R.id.table_main);

        //----< @Loop: Days >----
        for (int iDay=1;iDay<=31;iDay++) {
            //----< Day-Row >----
            //-< Date >-
            Date dtRow= clsHelper.getDate(2018,9,iDay);
            //< weekday >
            //*as string
            SimpleDateFormat fmtWeekday = new SimpleDateFormat("EE");
            String weekday = fmtWeekday.format(dtRow);
            //</ weekday >

            //*as weekday_number
            Calendar calendarDay=Calendar.getInstance();
            calendarDay.setTime(dtRow);
            int NrWeekday=calendarDay.get(Calendar.DAY_OF_WEEK);//  fmtWeekdayNr.format(dtRow);
            //-</ Date >-

            //--< Row >--
            TableRow row = new TableRow(this);
            if(NrWeekday== Calendar.SATURDAY || NrWeekday==Calendar.SUNDAY) {
                row.setBackgroundColor(Color.rgb(200, 200, 200));
            }

            //< dayNr >
            TextView lblDayNr = new TextView(this);
            lblDayNr.setText(String.valueOf(iDay) );    //*cast integer to string
            row.addView(lblDayNr);
            //</ dayNr >

            //--< weekday >--
            TextView lblWeekday = new TextView(this);
            lblWeekday.setText(weekday);
            row.addView(lblWeekday);
            //--</ weekday >--

            //--</ Row >--

            //< add to table >
            tbl.addView(row);
            //</ add to table >
            //----</ Day-Row >----
        }
        //-------</ create_Table() >--------
    }

}

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.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="com.codedocu.test02.MainActivity">

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="50dp"
        android:layout_marginLeft="2dp"
        android:layout_marginTop="2dp"
        android:onClick="btnStart_onClick"
        android:text="START"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <ScrollView
        android:id="@+id/scrollView1"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_marginTop="50dp"
        android:background="#3d455b"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent">

            <TableLayout
                android:id="@+id/table_main"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_centerHorizontal="true"
                android:background="#FFFF"
                android:padding="10px"
                >

                <TableRow android:layout_width="match_parent"
                    android:background="#000000"
                    >

                    <TextView
                        android:id="@+id/tblMonth"
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content"
                        android:background="@drawable/table_layout"
                        android:padding="10px"
                        android:text="day"
                        android:textColor="#FFFF"
                        />

                    <TextView
                        android:background="@drawable/table_layout"
                        android:padding="10px"
                        android:text=".." />
                </TableRow>

            </TableLayout>

    </ScrollView>
</android.support.constraint.ConstraintLayout>

android:background="@drawable/table_layout"