activity_main.xmlMainActivity.java
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    android:gravity="center"
    android:orientation="vertical"
    tools:context="com.codinginflow.handlerpostdelayedexample.MainActivity">

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="startRepeating"
        android:text="start repeating" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="stopRepeating"
        android:text="stop repeating" />

</LinearLayout>

package com.codinginflow.handlerpostdelayedexample;

import android.os.Handler;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
    private Handler mHandler = new Handler();

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

    public void startRepeating(View v) {
        //mHandler.postDelayed(mToastRunnable, 5000);
        mToastRunnable.run();
    }

    public void stopRepeating(View v) {
        mHandler.removeCallbacks(mToastRunnable);
    }

    private Runnable mToastRunnable = new Runnable() {
        @Override
        public void run() {
            Toast.makeText(MainActivity.this, "This is a delayed toast", Toast.LENGTH_SHORT).show();
            mHandler.postDelayed(this, 5000);
        }
    };
}