Create first android app using Android studio

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Step 1:
Step 2:
Step 3:
Step 4 :

In this post, we are going to create first android app which will show result of multiplication of two user input numbers. We have already created Android hello world example before but it was too basic.
We are going to design our screen as below:

We are not going to put much validations here. We will just create above screen which will show multiplication of two numbers in Result textview.

Steps for creating first android app using Android studio:

Step 1:

Create a new android project named “MultiplicationApp”. Provide Activity name as “MultiplicationActivity” instead of “HelloWorldActivity”.

Step 2:

Go to res -> layout -> activity_multiplication.xml. Paste following code in xml file to create multiplication screen.

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:tools="http://schemas.android.com/tools"
 android:id="@+id/activity_multiplication"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:paddingBottom="@dimen/activity_vertical_margin"
 android:paddingLeft="@dimen/activity_horizontal_margin"
 android:paddingRight="@dimen/activity_horizontal_margin"
 android:paddingTop="@dimen/activity_vertical_margin"
 tools:context="com.java2blog.multiplicationapp.MultiplicationActivity">

 <TextView
 android:text="Number 1"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:layout_alignParentTop="true"
 android:layout_alignParentLeft="true"
 android:layout_alignParentStart="true"
 android:layout_marginLeft="38dp"
 android:layout_marginStart="38dp"
 android:layout_marginTop="103dp"
 android:id="@+id/textView1"
 android:textSize="18sp" />

 <TextView
 android:text="Number 2"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:layout_alignParentLeft="true"
 android:layout_marginTop="206dp"
 android:layout_marginLeft="38dp"
 android:layout_marginStart="38dp"
 android:id="@+id/textView2"
 android:textSize="18sp" />
 <TextView
 android:text="Result"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:layout_alignParentLeft="true"
 android:layout_marginTop="309dp"
 android:layout_marginLeft="38dp"
 android:layout_marginStart="38dp"
 android:id="@+id/textView3"
 android:textSize="18sp" />

 <EditText
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:inputType="textPersonName"
 android:ems="10"
 android:layout_alignParentTop="true"
 android:layout_toRightOf="@+id/textView1"
 android:layout_toEndOf="@+id/textView1"
 android:layout_marginLeft="41dp"
 android:layout_marginStart="41dp"
 android:layout_marginTop="91dp"
 android:id="@+id/editText1" />
 <EditText
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:inputType="textPersonName"
 android:ems="10"
 android:layout_alignParentTop="true"
 android:layout_toRightOf="@+id/textView2"
 android:layout_toEndOf="@+id/textView2"
 android:layout_marginLeft="41dp"
 android:layout_marginStart="41dp"
 android:layout_marginTop="182dp"
 android:id="@+id/editText2" />

 <Button
 android:text="Multiply"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:layout_alignParentBottom="true"
 android:layout_toRightOf="@+id/textView2"
 android:layout_toEndOf="@+id/textView2"
 android:layout_marginBottom="48dp"
 android:id="@+id/button" />

 <TextView

 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:layout_alignTop="@+id/textView3"
 android:layout_toRightOf="@+id/button"
 android:layout_toEndOf="@+id/button"
 android:layout_marginLeft="35dp"
 android:layout_marginStart="35dp"
 android:id="@+id/textView4"
 android:textSize="18sp" />
</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

xmlns:tools="http://schemas.android.com/tools"

android:id="@+id/activity_multiplication"

android:layout_width="match_parent"

android:layout_height="match_parent"

android:paddingBottom="@dimen/activity_vertical_margin"

android:paddingLeft="@dimen/activity_horizontal_margin"

android:paddingRight="@dimen/activity_horizontal_margin"

android:paddingTop="@dimen/activity_vertical_margin"

tools:context="com.java2blog.multiplicationapp.MultiplicationActivity">

<TextView

android:text="Number 1"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_alignParentTop="true"

android:layout_alignParentLeft="true"

android:layout_alignParentStart="true"

android:layout_marginLeft="38dp"

android:layout_marginStart="38dp"

android:layout_marginTop="103dp"

android:id="@+id/textView1"

android:textSize="18sp" />

<TextView

android:text="Number 2"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_alignParentLeft="true"

android:layout_marginTop="206dp"

android:layout_marginLeft="38dp"

android:layout_marginStart="38dp"

android:id="@+id/textView2"

android:textSize="18sp" />

<TextView

android:text="Result"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_alignParentLeft="true"

android:layout_marginTop="309dp"

android:layout_marginLeft="38dp"

android:layout_marginStart="38dp"

android:id="@+id/textView3"

android:textSize="18sp" />

<EditText

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:inputType="textPersonName"

android:ems="10"

android:layout_alignParentTop="true"

android:layout_toRightOf="@+id/textView1"

android:layout_toEndOf="@+id/textView1"

android:layout_marginLeft="41dp"

android:layout_marginStart="41dp"

android:layout_marginTop="91dp"

android:id="@+id/editText1" />

<EditText

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:inputType="textPersonName"

android:ems="10"

android:layout_alignParentTop="true"

android:layout_toRightOf="@+id/textView2"

android:layout_toEndOf="@+id/textView2"

android:layout_marginLeft="41dp"

android:layout_marginStart="41dp"

android:layout_marginTop="182dp"

android:id="@+id/editText2" />

<Button

android:text="Multiply"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_alignParentBottom="true"

android:layout_toRightOf="@+id/textView2"

android:layout_toEndOf="@+id/textView2"

android:layout_marginBottom="48dp"

android:id="@+id/button" />

<TextView

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_alignTop="@+id/textView3"

android:layout_toRightOf="@+id/button"

android:layout_toEndOf="@+id/button"

android:layout_marginLeft="35dp"

android:layout_marginStart="35dp"

android:id="@+id/textView4"

android:textSize="18sp" />

</RelativeLayout>

Step 3:

Go to app -> java -> package -> MultiplicationActivity.java.
Change MultiplicationActivity.java as below:

package com.java2blog.multiplicationapp;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

public class MultiplicationActivity extends AppCompatActivity {

    private EditText edittext1,edittext2;
    private TextView textView;
    private Button buttonMulti;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_multiplication);
        multiplyOnButtonClick();
    }

    public void multiplyOnButtonClick(){
        edittext1=(EditText)findViewById(R.id.editText1);
        edittext2=(EditText)findViewById(R.id.editText2);
        textView=(TextView) findViewById(R.id.textView4);
        buttonMulti=(Button)findViewById(R.id.button);

        buttonMulti.setOnClickListener(new OnClickListener(){

            @Override
            public void onClick(View view) {
                String value1=edittext1.getText().toString();
                String value2=edittext2.getText().toString();
                Double num1=Double.parseDouble(value1);
                Double num2=Double.parseDouble(value2);
                double multi=num1*num2;
                textView.setText(""+multi);
                Toast.makeText(getApplicationContext(),String.valueOf(multi),Toast.LENGTH_LONG).show();
            }

        });

    }
}

package com.java2blog.multiplicationapp;

import android.os.Bundle;

import android.support.v7.app.AppCompatActivity;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.Button;

import android.widget.EditText;

import android.widget.TextView;

import android.widget.Toast;

public class MultiplicationActivity extends AppCompatActivity {

private EditText edittext1,edittext2;

private TextView textView;

private Button buttonMulti;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_multiplication);

multiplyOnButtonClick();

}

public void multiplyOnButtonClick(){

edittext1=(EditText)findViewById(R.id.editText1);

edittext2=(EditText)findViewById(R.id.editText2);

textView=(TextView) findViewById(R.id.textView4);

buttonMulti=(Button)findViewById(R.id.button);

buttonMulti.setOnClickListener(new OnClickListener(){

@Override

public void onClick(View view) {

String value1=edittext1.getText().toString();

String value2=edittext2.getText().toString();

Double num1=Double.parseDouble(value1);

Double num2=Double.parseDouble(value2);

double multi=num1*num2;

textView.setText(""+multi);

Toast.makeText(getApplicationContext(),String.valueOf(multi),Toast.LENGTH_LONG).show();

}

});

}

To get any widget reference in activity class, you can use id which you have defined in layout xml file. So to get reference for editText corresponds to “Number 1” in the screen, we have used below code:

EditText edittext1=(EditText)findViewById(R.id.editText1);

EditText edittext1=(EditText)findViewById(R.id.editText1);

You can get text entered by user in that edit text by using below code:

String value1=edittext1.getText().toString();

String value1=edittext1.getText().toString();

We have also put click listener on button named “Multiply”.

 buttonMulti.setOnClickListener(new OnClickListener(){

            @Override
            public void onClick(View view) {
                String value1=edittext1.getText().toString();
                String value2=edittext2.getText().toString();
                Double num1=Double.parseDouble(value1);
                Double num2=Double.parseDouble(value2);
                double multi=num1*num2;
                textView.setText(""+multi);
                Toast.makeText(getApplicationContext(),String.valueOf(multi),Toast.LENGTH_LONG).show();
            }

        });

buttonMulti.setOnClickListener(new OnClickListener(){

@Override

public void onClick(View view) {

String value1=edittext1.getText().toString();

String value2=edittext2.getText().toString();

Double num1=Double.parseDouble(value1);

Double num2=Double.parseDouble(value2);

double multi=num1*num2;

textView.setText(""+multi);

Toast.makeText(getApplicationContext(),String.valueOf(multi),Toast.LENGTH_LONG).show();

}

});

Step 4 :

Run the app. When you run above app on emulator, you will get below screen:

Provide user input numbers and click on multiply, you will get the result.

We are done with first android app using android studio.
Happy Android Learning!!

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Create first android app using Android studio

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