How to programmatically turn on Wifi on Android device?

This example demonstrates how do I programmatically turn on wifi in android device.

Step 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project.

Step 2 − Add the following code to res/layout/activity_main.xml.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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:gravity="center"
   android:orientation="vertical"
   tools:context=".MainActivity">
   <Button
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="Wifi On!"
      android:onClick="enableWifi"/>
   <Button
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="Wifi Off!"
      android:onClick="disableWifi" />
</LinearLayout>

Step 3 − Add the following code to src/MainActivity.java

import android.content.Context;
import android.net.wifi.WifiManager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity {
   private WifiManager wifiManager;
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      wifiManager = (WifiManager) getApplicationContext().getSystemService(Context.WIFI_SERVICE);
   }
   public void enableWifi(View view){
      wifiManager.setWifiEnabled(true);
      Toast.makeText(this, "Wifi enabled", Toast.LENGTH_SHORT).show();
   }
   public void disableWifi(View view){
      wifiManager.setWifiEnabled(false);
      Toast.makeText(this, "Wifi Disabled", Toast.LENGTH_SHORT).show();
   }
}

Step 4 - Add the following code to androidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="app.com.sample">
   <uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>
   <uses-permission android:name="android.permission.CHANGE_WIFI_STATE"/>
   <application
      android:allowBackup="true"
      android:icon="@mipmap/ic_launcher"
      android:label="@string/app_name"
      android:roundIcon="@mipmap/ic_launcher_round"
      android:supportsRtl="true"
      android:theme="@style/AppTheme">
      <activity android:name=".MainActivity">
         <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
         </intent-filter>
      </activity>
   </application>
</manifest>

Let's try to run your application. I assume you have connected your actual Android Mobile device with your computer. To run the app from android studio, open one of your project's activity files and click Run  Icon from the toolbar. Select your mobile device as an option and then check your mobile device which will display your default screen –