Android Programming Lab

Create a simple application to change colors of background of any textbox with the click of a button.

                        
package com.example.myapplication;

import android.graphics.Color;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

import androidx.activity.EdgeToEdge;
import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {
    private String colors[] = {"#FF9800","#03A9F4", "#9067D9", "#FFEB3B"};
    private int i = 0;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        EdgeToEdge.enable(this);
        setContentView(R.layout.activity_main);
        Button myBtn = findViewById(R.id.button);
        TextView myTxt = findViewById(R.id.textView);
        myBtn.setOnClickListener(new View.OnClickListener()
        {
            @Override
            public void onClick(View v) {
                myTxt.setBackgroundColor(Color.parseColor(colors[i]));
                i++;
                if(i>3){
                    i = 0;
                }
            }
        });
    }

}

                        
<?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:id="@+id/main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:background="#5DE063"
        android:text="Button"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.462"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.522" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="252dp"
        android:background="#FFEB3B"
        android:text="Changing Background Colors"
        app:layout_constraintBottom_toTopOf="@+id/button"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.456"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="1.0" />

</androidx.constraintlayout.widget.ConstraintLayout>

Create a simple app to change background colour on button click.

                        
package com.example.myapplication;

import android.graphics.Color;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

import androidx.activity.EdgeToEdge;
import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {
    private String colors[] = {"#FF9800","#03A9F4", "#9067D9", "#FFEB3B"};
    private int i = 0;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        EdgeToEdge.enable(this);
        setContentView(R.layout.activity_main);
        View rootview = findViewById(R.id.main);
        Button myBtn = findViewById(R.id.button);
        myBtn.setOnClickListener(new View.OnClickListener()
        {
            @Override
            public void onClick(View v) {
                rootview.setBackgroundColor(Color.parseColor(colors[i]));
                i++;
                if(i>3){
                    i = 0;
                }
            }
        });
    }
}

                        
<?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:id="@+id/main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:background="#5DE063"
        android:text="Click Me to change Background Color"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.462"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.522" />

</androidx.constraintlayout.widget.ConstraintLayout>

Create a simple app to add two numbers.

                        
package com.example.myapplication;

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

import androidx.activity.EdgeToEdge;
import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Button myBtn = findViewById(R.id.button);
        EditText num1 = findViewById(R.id.editTextNumber1);
        EditText num2 = findViewById(R.id.editTextNumber2);
        EditText displayRes = findViewById(R.id.editTextNumber3);

        myBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String num1Text = num1.getText().toString();
                String num2Text = num2.getText().toString();

                // Check if either field is empty
                if (num1Text.isEmpty() || num2Text.isEmpty()) {
                    Toast.makeText(MainActivity.this, "Please enter both numbers", Toast.LENGTH_SHORT).show();
                    return; // Exit the method
                }

                // Parse the numbers and sum them
                int number1 = Integer.parseInt(num1Text);
                int number2 = Integer.parseInt(num2Text);
                int result = number1 + number2;

                // Display the result
                displayRes.setText(result + "");
            }
        });
    }
}

                        
<?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:id="@+id/main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <EditText
        android:id="@+id/editTextText2"
        android:layout_width="87dp"
        android:layout_height="42dp"
        android:ems="10"
        android:inputType="text"
        android:text="Num 1:"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.079"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.023" />

    <EditText
        android:id="@+id/editTextNumber1"
        android:layout_width="232dp"
        android:layout_height="45dp"
        android:ems="10"
        android:inputType="number"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.92"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.023" />

    <EditText
        android:id="@+id/editTextText3"
        android:layout_width="89dp"
        android:layout_height="45dp"
        android:ems="10"
        android:inputType="text"
        android:text="Num 2:"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.08"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.12" />

    <EditText
        android:id="@+id/editTextNumber2"
        android:layout_width="230dp"
        android:layout_height="46dp"
        android:ems="10"
        android:inputType="number"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.911"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.121" />

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Add"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.26" />

    <EditText
        android:id="@+id/editTextText4"
        android:layout_width="95dp"
        android:layout_height="45dp"
        android:ems="10"
        android:inputType="text"
        android:text="Sum = "
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.097"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.441" />

    <EditText
        android:id="@+id/editTextNumber3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:ems="10"
        android:inputType="number"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.805"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.441" />
</androidx.constraintlayout.widget.ConstraintLayout>