Check for updates in the play store and prompt user to update if an update is available.

Versionator.java

package com.geneticcoder.Versionator;

// Check here for updates: https://gist.github.com/Pamblam/53cb2b1c90dea09d4872084956d17b5c

import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.app.AlertDialog;

import com.squareup.okhttp.OkHttpClient;
import com.squareup.okhttp.Request;
import com.squareup.okhttp.Response;


import java.io.IOException;

public class Versionator {

    private Context context;

    public static String packageName = null;

    public Versionator(Context c){
        context = c;
        packageName = context.getPackageName();
    }

    public Versionator setPackageName(String packageName){
        this.packageName = packageName;
        return this;
    }

    public void checkUpdate(){
        new AsyncTask<String, Void, Bundle>() {
            @Override
            protected Bundle doInBackground(String... params) {
                String html = "<div class=\"content\" itemprop=\"softwareVersion\"> 0 </div>";
                try {

                    OkHttpClient client = new OkHttpClient();
                    Request request = new Request.Builder()
                            .url("https://play.google.com/store/apps/details?id="+packageName+"&hl=en")
                            .build();
                    Response response = client.newCall(request).execute();
                    html = response.body().string();
                }catch (IOException e){e.printStackTrace();}
                html = html.substring(html.indexOf("Current Version</div><div><span class=\"")+46);
                html = html.substring(0,html.indexOf("<"));
                float vn = Float.valueOf(html);
                float cvn = 0;
                try {
                    String vname = context.getPackageManager().getPackageInfo(context.getPackageName(), 0).versionName;
                    cvn = Float.valueOf(vname);
                }catch (PackageManager.NameNotFoundException e){e.printStackTrace();}
                Bundle b = new Bundle();
                b.putFloat("LatestVersion",vn);
                b.putFloat("CurrentVersion",cvn);
                b.putBoolean("UpdateAvailable", vn>cvn);
                return b;
            }
            @Override
            protected void onPostExecute(Bundle result) {
                if(result.getBoolean("UpdateAvailable")){
                    updateAvailable(result);
                }else{
                    done();
                }
            }
        }.execute();
    }

    //  override this...
    public void done(){
        Log.i("Versionator", "No updates available");
    }

    public void updateAvailable(Bundle updateInfo){
        AlertDialog alertDialog = new AlertDialog.Builder(context).create();
        alertDialog.setCancelable(false);
        alertDialog.setCanceledOnTouchOutside(false);
        alertDialog.setTitle("Update Available!");
        alertDialog.setMessage("Version "+updateInfo.getFloat("LatestVersion")+" has been released. "+
                "You are currently using version "+updateInfo.getFloat("CurrentVersion")+". "+
                "Would you like to update now?");
        alertDialog.setButton(AlertDialog.BUTTON_POSITIVE, "Update",
                new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int which) {
                        try {
                            context.startActivity(new Intent(Intent.ACTION_VIEW, Uri.parse("market://details?id=" + packageName)));
                        } catch (android.content.ActivityNotFoundException anfe) {
                            context.startActivity(new Intent(Intent.ACTION_VIEW, Uri.parse("https://play.google.com/store/apps/details?id=" + packageName)));
                        }
                        dialog.dismiss();
                    }
                });
        alertDialog.setButton(AlertDialog.BUTTON_NEGATIVE, "Not now",
                new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int which) {
                        done();
                        dialog.dismiss();
                    }
                });
        alertDialog.show();
        Log.i("Versionator", "Updates available");
    }

}

Versionator.md

Updated Apr. 4 '18 to take into account recent changes in Playstore

Notes & prerequisites

• Uses the version name, not the build number. The build number is not publicly available on the play store. Therefore, version name must be castable to a float.
• Requires okhttp & internet permissions
• Don't forget to change the package name in the class file
• If update is available, will show dialog asking user to update. If user chooses to update, will open the play store. If not, the done() method is called.

Requires okhttp & internet permissions...

In the gradle file...

dependencies {
    compile 'com.squareup.okhttp:okhttp:2.5.0'
}

In the manifest...

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

Sample usage

new Versionator(this){
    @Override
    public void done(){
        // Check is done, no update is available
        // Navigate to next activity or whatever..
    }
}.checkUpdate();