Timer using Rxjava in android Interval operator

Checkout the previous posts

1. Rxjava Introduction

2. Reactive Hello world application in android

3. Transformation using RxJava tutorial for beginners

4. Introducing Operators in RxJava tutorial for beginners

Interval create an Observable that emits a sequence of integers spaced by a given time interval

1) Create an activity as follows

package com.cretlabs.rxjavaintroduction;

import android.os.Bundle;
import android.os.Handler;
import android.support.v7.app.AppCompatActivity;
import android.widget.Button;
import android.widget.TextView;

import java.util.Locale;
import java.util.concurrent.TimeUnit;

import io.reactivex.Observable;
import io.reactivex.disposables.Disposable;

public class TimerActivity extends AppCompatActivity {
    Disposable disposable;
    Button start, stop;
    TextView textView;
    private long seconds;
    private Handler handler = new Handler();


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_timer);
        start = findViewById(R.id.button);
        stop = findViewById(R.id.button2);
        textView = findViewById(R.id.textView);
        start.setOnClickListener(view -> {
            startTimer();
        });
        stop.setOnClickListener(view -> {
            stopTimer();
        });


    }

    private void stopTimer() {
        if (disposable != null) {
            disposable.dispose();
        }
    }

    private void startTimer() {
        disposable = Observable.interval(1, TimeUnit.SECONDS)
                .map((tick) -> {
                    seconds += 1;
                    handler.post(() -> textView.setText(String.format(Locale.getDefault(), "%ds", seconds)));
                    return true;
                }).subscribe();
    }
}

2)activity_timer.xnl as follows

<?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.cretlabs.rxjavaintroduction.TimerActivity">

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="52dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:text="Start"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/button2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginTop="8dp"
        android:text="End"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="206dp"
        android:layout_height="99dp"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:gravity="center"
        android:textStyle="bold"
        android:textSize="30sp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
</android.support.constraint.ConstraintLayout>

Thanks happy Coding 😀

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