如何在 android 中每 5 秒在后台无限运行特定方法？

Question

I am developing a Vaccine Viewer app and I want to implement a function that run till vaccine get available.

Here is my vaccine checker method

boolean checkVaccine(String pinCode,String data){
    isVaccineAvailable = false;
    String url = "https://cdn-api.co-vin.in/api/v2/appointment/sessions/public/calendarByPin?pincode="+pinCode+"&date="+data;

    JsonObjectRequest request = new JsonObjectRequest(Request.Method.GET, url, null,
            new Response.Listener<JSONObject>() {
                @Override
                public void onResponse(JSONObject response) {

                    try {

                        JSONArray dataArray = response.getJSONArray("centers");

                        if(dataArray.length()==0){
                            Toast.makeText(MainActivity.this,"No Center Available",Toast.LENGTH_SHORT).show();
                        }
                        for(int i=0;i<dataArray.length();i++){
                            JSONObject centers = dataArray.getJSONObject(i);

                            String centerName = centers.getString("name");
                            String centerAddress = centers.getString("address");
                            String vaccinationStartTime = centers.getString("from");
                            String vaccinationEndTime = centers.getString("to");
                            String vaccinePrice = centers.getString("fee_type");

                            JSONObject sessions = centers.getJSONArray("sessions").getJSONObject(0);
                            int minimumAge = sessions.getInt("min_age_limit");
                            String vaccineName = sessions.getString("vaccine");
                            int totalVaccineAvailable = sessions.getInt("available_capacity");

                            if(totalVaccineAvailable>0){
                                isVaccineAvailable = true;
                            }

                            vaccinationData addData = new vaccinationData(centerName,
                                    centerAddress,vaccinationStartTime,vaccinationEndTime,
                                    vaccinePrice,vaccineName,totalVaccineAvailable,minimumAge);

                            dataList.add(addData);

                        }

                        vaccinationDataAdapter adapter = new vaccinationDataAdapter(MainActivity.this,dataList);
                        recyclerView.setAdapter(adapter);

                    }catch (JSONException e){
                        Toast.makeText(MainActivity.this,"Unable To Get Data From Server.",Toast.LENGTH_SHORT).show();
                    }

                }
            }, new Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError error) {

            Toast.makeText(MainActivity.this,"Unable To Get Data From Server.\nMake Sure Your Internet Connection ON.",Toast.LENGTH_SHORT).show();
        }
    });
    queue.add(request);
    return isVaccineAvailable;
}

I want to run above methods till function not return true. I was searched but I am unable to understand what exact I have to use? And How?

There are Handler, TimerTask, Runnable to repeat a task after few seconds and I got Job Scheduler but that need api <=21 And I want to give support for <=18, but I am not getting How to do this in background?

I tried below Code in MainActivity, but after calling that app get stuck and restart. I am beginner in android development, I dont know much more about service, and broadcast receiver.

while(!checkVaccine(pinCode,date)){
                    Handler waitForFiveSeconds = new Handler();
                    waitForFiveSeconds.postDelayed(new Runnable() {
                        @Override
                        public void run() {

                        }
                    },5000);
                    dataList.clear();
                }

                Toast.makeText(MainActivity.this,"Vaccine Is AVailable.",Toast.LENGTH_SHORT).show();

                notifyToTheUser();

What I have to use to repeat checkVaccine method forever in background after every 5 Seconds?

Answer 1

What you are looking for is background service. You can run operation in a background service for a long time. As you want to run these infinitely, this won't work as android has put some limitations prior Android O so your service would be stopped at some point

These are some articles on how to create it and it's limitations

https://www.tutorialspoint.com/how-to-create-background-service-in-android

https://medium.com/@kevalpatel2106/how-to-handle-background-services-in-android-o-f96783e65268

This is not a good approach to run any task infinitely in the background and indeed it is a bad practice. This will drain battery and system resources.

You want to build something which notifies you when vaccines get available for a certain Pincode, you should build something which runs on servers and sends you a notification when it is available, not your device checking every 5 seconds for it.

You could build a Telegram bot and deploy your application on a service like Heroku or AWS.

I want to let you know, that cowin API is Geo-Restricted so if you built something server-side it won't work at all if you choose any instance that is not located in India, You need an Indian server instance to make this work.

Answer 2

I got the solution of my answer by watching this video .

I have to use Thread Or Runnable Interface to do that in background.