Android Simple Login App

So lets gets started with our basic Android Simple Login App:

• Open your Android Studio.

• Click on Start a New Android Studio Project.

• Write your Application Name “LoginApp”  and leave other fields blank as it is, then click NEXT.

• Select the Minimum SDK “API 15: Android 4.0.3(IceCreamSandwich)”. I selected API 15 because it covers 94% device and it has almost all the features. If you want to cover 100% device then you can select API 8: Android 2.2(Froyo). But it has limitation on features. After selecting your API click on NEXT.

• Select the blank activity and click NEXT.

• Write the activity name “Login” and leave everything as it is. Click Finish.

• After clicking Finish, it takes around 5 minutes to build your first activity, which is Login Activity
•  .
• Now we will create another activity called “Main”.  This activity will redirect user to “User screen” after he provides valid Login and password.
• To create a new activity go to app -> res -> layout. Right click on layout and go to  new -> Activity -> Blank Activity.
• You will see the new activity screen.
• Write the name of your new activity as “Main” and leave everything as it is. Click Finish.
• Now we have two activities, which you can see in app -> res -> layout .
  • activity_login.xml
  • activity_main.xml
• Go to the activity_main.xml file. You can see the path of your user activity.                           
• activity_main.xml

<?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:layout_width="match_parent"

    android:layout_height="match_parent"

    android:paddingLeft="@dimen/activity_horizontal_margin"

    tools:context="com.example.nupur.loginapp.MainActivity">

    <TextView

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:layout_centerInParent="true"

        android:textSize="20dp"

        android:paddingLeft="10dp"

        android:textStyle="bold"

        android:text="Welcome to Formula/JEE Medical"

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




</RelativeLayout>

Go to AndroidManifest.xml file.




You will see your both activities. One is login activity which is also the launcher activity . Other is user activity. Here we set the Intent filter for our second activity which is also called as user activity.
AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android"    package="com.example.nupur.loginapp">

    <application        android:allowBackup="true"        android:icon="@mipmap/ic_launcher"        android:label="@string/app_name"        android:supportsRtl="true"        android:theme="@style/AppTheme">
        <activity android:name=".Login">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity android:name=".MainActivity"></activity>
    </application>

</manifest>



We will start with designing our Login Activity for our Android Simple Login App. Go to app -> res -> layout -> activity_login.xml.


Pick 5 large text elements, 1 person name element, 1 Button and 1 password element from palette. Arrange it as shown in the image below:


Change the text and id as below:

Text: Login Page, Id: textView_login
Text: Username, Id: textView_username
Text: Password, Id: textView_password
Text: ” “, Id: editText_user
Text: ” “, id: editText_password
Text: Attempt, id: textView_attempt
Text: ” “, Id: textView_attempt_count
Text: “Login“, Id: button_login




Define strings constant for all the elements in strings.xml file. You can find string.xml file in  app -> res -> values ->strings.xml.



strings.xml





<resources>
    <string name="app_name">LoginApp</string>

</resources>


Now we will design the second activity which is user activity. Go to app -> res ->layout -> activity_user.xml.


Select large text element from the palette. Edit its text to “welcome to Formula/JEE Medical “.
In this part we will see how to write the code behind login button. And how to validate the username and password.

Go to the java file in which we will do code for the action performed by button.


Go to app -> Java -> Com.abhinavhackpundit.loginapp ->login.

The code or logic behind the action of app is shown below:
login.java


package com.example.nupur.loginapp;

import android.content.Intent;

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

public class Login extends AppCompatActivity {
    private static EditText username;
    private static EditText password;
    private static TextView attempt;
    private static Button login_button;
    int attempt_counter=5;

    @Override    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);
        username = (EditText)findViewById(R.id.editText_user);
        password = (EditText)findViewById(R.id.editText_password);
        attempt = (TextView)findViewById(R.id.textView_attempt);
        login_button = (Button)findViewById(R.id.button_login);
        LoginButton();
    }

    public void LoginButton(){
        attempt.setText(Integer.toString(attempt_counter));
        login_button.setOnClickListener(
                new View.OnClickListener() {
                    @Override                    public void onClick(View v) {
                        if (username.getText().toString().equals("admin")&&
                        password.getText().toString().equals("pass123")){
                            Toast.makeText(Login.this, "Username and password is correct",Toast.LENGTH_SHORT).show();
                            //Here intent is used to goto Welcome page or start new activity i.e. MainActivity                            Intent intent = new Intent(Login.this,MainActivity.class);
                            startActivity(intent);
                            finish();
                        }
                        else {
                            Toast.makeText(Login.this,"Username and password is NOT correct",
                                    Toast.LENGTH_SHORT).show();
                            attempt_counter--;
                            attempt.setText(Integer.toString(attempt_counter));
                            if(attempt_counter==0)
                                login_button.setEnabled(false);
                        }
                    }
                }
        );
    }
}




Click on Run. You can see your Android Login App running.


Thank you for reading this article. If you face any problem or having any doubts, just let me know in comment box