Convert your Website into Professional Android App Using Android Studio

1. WebView Android App Code:

Activity_Main.xml

<WebView
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:id="@+id/webView"
    android:layout_alignParentTop="true"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:layout_alignParentBottom="true"
    android:layout_alignParentRight="true"
    android:layout_alignParentEnd="true"
    tools:ignore="MissingConstraints" />

MainActivity.java

import android.os.Bundle;
import android.webkit.WebView;
import android.webkit.WebViewClient;

import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {

    String websiteURL = "https://shop.trusof.com/"; // sets web url
    private WebView webview;

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

        //Webview stuff
        webview = findViewById(R.id.webView);
        webview.getSettings().setJavaScriptEnabled(true);
        webview.getSettings().setDomStorageEnabled(true);
        webview.setOverScrollMode(WebView.OVER_SCROLL_NEVER);
        webview.loadUrl(websiteURL);
        webview.setWebViewClient(new WebViewClientDemo());

    }

    private class WebViewClientDemo extends WebViewClient {
        @Override
        //Keep webview in app when clicking links
        public boolean shouldOverrideUrlLoading(WebView view, String url) {
            view.loadUrl(url);
            return true;
        }
    }

}

AndroidManifest.xml 

<uses-permission android:name="android.permission.INTERNET" />

2. Internet Connection Error:

AndroidManifest.xml

<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>

MainActivity.java

import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.Bundle;
import android.util.Log;
import android.webkit.WebView;
import android.webkit.WebViewClient;

import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {

    String websiteURL = "https://shop.trusof.com/"; // sets web url
    private WebView webview;

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

        if( ! CheckNetwork.isInternetAvailable(this)) //returns true if internet available
        {
            //if there is no internet do this
            setContentView(R.layout.activity_main);
            //Toast.makeText(this,"No Internet Connection, Chris",Toast.LENGTH_LONG).show();

            new AlertDialog.Builder(this) //alert the person knowing they are about to close
                    .setTitle("No internet connection available")
                    .setMessage("Please Check you're Mobile data or Wifi network.")
                    .setPositiveButton("Ok", new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialog, int which) {
                            finish();
                        }
                    })
                    //.setNegativeButton("No", null)
                    .show();

        }
        else
        {
            //Webview stuff
            webview = findViewById(R.id.webView);
            webview.getSettings().setJavaScriptEnabled(true);
            webview.getSettings().setDomStorageEnabled(true);
            webview.setOverScrollMode(WebView.OVER_SCROLL_NEVER);
            webview.loadUrl(websiteURL);
            webview.setWebViewClient(new WebViewClientDemo());

        }
    }


    private class WebViewClientDemo extends WebViewClient {
        @Override
        //Keep webview in app when clicking links
        public boolean shouldOverrideUrlLoading(WebView view, String url) {
            view.loadUrl(url);
            return true;
        }
    }


}

class CheckNetwork {

    private static final String TAG = CheckNetwork.class.getSimpleName();

    public static boolean isInternetAvailable(Context context)
    {
        NetworkInfo info = (NetworkInfo) ((ConnectivityManager)
                context.getSystemService(Context.CONNECTIVITY_SERVICE)).getActiveNetworkInfo();

        if (info == null)
        {
            Log.d(TAG,"no internet connection");
            return false;
        }
        else
        {
            if(info.isConnected())
            {
                Log.d(TAG," internet connection available...");
                return true;
            }
            else
            {
                Log.d(TAG," internet connection");
                return true;
            }

        }
    }
}

3. Back & Exit Feature:

MainActivity.java

//set back button functionality
@Override
public void onBackPressed() { //if user presses the back button do this
    if (webview.isFocused() && webview.canGoBack()) { //check if in webview and the user can go back
        webview.goBack(); //go back in webview
    } else { //do this if the webview cannot go back any further

        new AlertDialog.Builder(this) //alert the person knowing they are about to close
                .setTitle("EXIT")
                .setMessage("Are you sure. You want to close this app?")
                .setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        finish();
                    }
                })
                .setNegativeButton("No", null)
                .show();
    }
}

4. Swipe Down to Refresh:

activity_main.xml

<androidx.swiperefreshlayout.widget.SwipeRefreshLayout
    android:id="@+id/swipeContainer"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <WebView
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:id="@+id/webView"
        android:layout_alignParentTop="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_alignParentBottom="true"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true"
        tools:ignore="MissingConstraints" />

</androidx.swiperefreshlayout.widget.SwipeRefreshLayout>

MainActivity.java

SwipeRefreshLayout mySwipeRefreshLayout;

//Swipe to refresh functionality
mySwipeRefreshLayout = (SwipeRefreshLayout)this.findViewById(R.id.swipeContainer);

mySwipeRefreshLayout.setOnRefreshListener(
        new SwipeRefreshLayout.OnRefreshListener() {
            @Override
            public void onRefresh() {
                webview.reload();
            }
        }
);

private class WebViewClientDemo extends WebViewClient {
    @Override
    //Keep webview in app when clicking links
    public boolean shouldOverrideUrlLoading(WebView view, String url) {
        view.loadUrl(url);
        return true;
    }
    @Override
    public void onPageFinished(WebView view, String url) {
        super.onPageFinished(view, url);
        mySwipeRefreshLayout.setRefreshing(false);
    }
}

import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.Bundle;
import android.util.Log;
import android.webkit.WebView;
import android.webkit.WebViewClient;

import androidx.appcompat.app.AppCompatActivity;
import androidx.swiperefreshlayout.widget.SwipeRefreshLayout;

public class MainActivity extends AppCompatActivity {

    String websiteURL = "https://shop.trusof.com/"; // sets web url
    private WebView webview;
    SwipeRefreshLayout mySwipeRefreshLayout;

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

        if( ! CheckNetwork.isInternetAvailable(this)) //returns true if internet available
        {
            //if there is no internet do this
            setContentView(R.layout.activity_main);
            //Toast.makeText(this,"No Internet Connection, Chris",Toast.LENGTH_LONG).show();

            new AlertDialog.Builder(this) //alert the person knowing they are about to close
                    .setTitle("No internet connection available")
                    .setMessage("Please Check you're Mobile data or Wifi network.")
                    .setPositiveButton("Ok", new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialog, int which) {
                            finish();
                        }
                    })
                    //.setNegativeButton("No", null)
                    .show();

        }
        else
        {
            //Webview stuff
            webview = findViewById(R.id.webView);
            webview.getSettings().setJavaScriptEnabled(true);
            webview.getSettings().setDomStorageEnabled(true);
            webview.setOverScrollMode(WebView.OVER_SCROLL_NEVER);
            webview.loadUrl(websiteURL);
            webview.setWebViewClient(new WebViewClientDemo());

        }

        //Swipe to refresh functionality
        mySwipeRefreshLayout = (SwipeRefreshLayout)this.findViewById(R.id.swipeContainer);

        mySwipeRefreshLayout.setOnRefreshListener(
                new SwipeRefreshLayout.OnRefreshListener() {
                    @Override
                    public void onRefresh() {
                        webview.reload();
                    }
                }
        );

    }


    private class WebViewClientDemo extends WebViewClient {
        @Override
        //Keep webview in app when clicking links
        public boolean shouldOverrideUrlLoading(WebView view, String url) {
            view.loadUrl(url);
            return true;
        }
        @Override
        public void onPageFinished(WebView view, String url) {
            super.onPageFinished(view, url);
            mySwipeRefreshLayout.setRefreshing(false);
        }
    }

    //set back button functionality
    @Override
    public void onBackPressed() { //if user presses the back button do this
        if (webview.isFocused() && webview.canGoBack()) { //check if in webview and the user can go back
            webview.goBack(); //go back in webview
        } else { //do this if the webview cannot go back any further

            new AlertDialog.Builder(this) //alert the person knowing they are about to close
                    .setTitle("EXIT")
                    .setMessage("Are you sure. You want to close this app?")
                    .setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialog, int which) {
                            finish();
                        }
                    })
                    .setNegativeButton("No", null)
                    .show();
        }
    }

}

class CheckNetwork {

    private static final String TAG = CheckNetwork.class.getSimpleName();

    public static boolean isInternetAvailable(Context context)
    {
        NetworkInfo info = (NetworkInfo) ((ConnectivityManager)
                context.getSystemService(Context.CONNECTIVITY_SERVICE)).getActiveNetworkInfo();

        if (info == null)
        {
            Log.d(TAG,"no internet connection");
            return false;
        }
        else
        {
            if(info.isConnected())
            {
                Log.d(TAG," internet connection available...");
                return true;
            }
            else
            {
                Log.d(TAG," internet connection");
                return true;
            }

        }
    }
}

5. Screen Rotation:

AndroidManifest.xml

android:screenOrientation="portrait">