Toast Using

MainActivity.java

package com.codewithahsan.dummyapp;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    public void send(View view) {
        Toast.makeText(this, "Sending data from app...", Toast.LENGTH_SHORT).show();
    }
    public void receive(View view) {
        Toast.makeText(this, "Receiving data from app...", Toast.LENGTH_SHORT).show();
    }
    public void delete(View view) {
        Toast.makeText(this, "Deleting data from app...", Toast.LENGTH_SHORT).show();
    }

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

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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=".MainActivity">

    <ImageView
        android:id="@+id/imageView3"
        android:layout_width="249dp"
        android:layout_height="250dp"
        android:layout_marginTop="125dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:srcCompat="@mipmap/ic_launcher_round" />

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="50dp"
        android:layout_marginLeft="50dp"
        android:onClick="send"
        android:text="@string/send_message"
        app:layout_constraintBaseline_toBaselineOf="@+id/button2"
        app:layout_constraintStart_toStartOf="parent" />

    <Button
        android:id="@+id/button2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="115dp"
        android:onClick="receive"
        android:text="@string/receive_message"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toStartOf="@+id/button3"
        app:layout_constraintHorizontal_bias="0.479"
        app:layout_constraintStart_toEndOf="@+id/button"
        app:layout_constraintTop_toBottomOf="@+id/imageView3"
        app:layout_constraintVertical_bias="0.182" />

    <Button
        android:id="@+id/button3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="50dp"
        android:layout_marginRight="50dp"
        android:onClick="delete"
        android:text="@string/delete_message"
        app:layout_constraintBaseline_toBaselineOf="@+id/button2"
        app:layout_constraintEnd_toEndOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>

string.xml

<resources>
    <string name="app_name">Dummy App</string>
    <string name="send_message">Send</string>
    <string name="receive_message">Receive</string>
    <string name="delete_message">Delete</string>
</resources>