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How can I perform a task on an activity in Android without having to open that activity or when away from that activity?

I have an activity in Android from where I want to send email to a predefined email ID automatically at a particular point in time when I am either on other activities in the application or not on the application itself. How can I do that?
I am using broadcast receiver like this - code below
private void startMinuteUpdated() {
IntentFilter intentFilter = new IntentFilter();
intentFilter.addAction(Intent.ACTION_TIME_TICK);
minuteUpdateReceiver= new BroadcastReceiver() {
#RequiresApi(api = Build.VERSION_CODES.O)
#Override
public void onReceive(Context context, Intent intent) {
//perform a certain task like send email at a particular time
}
};
registerReceiver(minuteUpdateReceiver, intentFilter);
}
#Override
protected void onResume() {
super.onResume();
startMinuteUpdated();
}
#Override
protected void onPause() {
super.onPause();
startMinuteUpdated();
unregisterReceiver(minuteUpdateReceiver);
}

How to pass a variable from activities to start a CountDownTimer service?

This is my first question and I've been trying to find a solution to this for hours but can't get it to work. I'm building an android app that takes an input from the user (number of hours) to fast (not eat). The input is then taken to the service where it does a countdown in the background. Along the way, I'd like the user to access other activities that could you the results from the countdown timer (eg, time_left/total_time = percentage complete). So far, my button that I've created works to make the call for the service. but the service never gets called to update the text view. Thanks
Here is what I have,
public class StartFast extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_start_fast);
startService(new Intent(this, MyService.class));
Log.i("Started service", "hello started service...");
registerReceiver(br, new IntentFilter("COUNTDOWN_UPDATED"));
}
private BroadcastReceiver br = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent) {
intent.getExtras();
long millisUntilFinished = intent.getLongExtra("countdown",0);
String time = Long.toString((millisUntilFinished));
TextView tv = findViewById(R.id.timeView1);
tv.setText(time);
}
};
public void BeginFast(View view){
//Intent intent = new Intent( this, StartFast.class);
// below is how to pass an intent for use in a Service to run in the backgroun
Intent intent =new Intent(this, MyService.class);
startService(intent);
// intent.putExtra() // putExtra longs ...will do after static run succeeds
//intent.putExtra("data", data); //adding the data
Intent intent1 = new Intent(this, Heart.class);
startActivity(intent1);
}
}
and here is the service class,
public class MyService extends Service {
private final static String TAG = "MyService";
public static final String COUNTDOWN_BR = "FastBreak.countdown_br";
Intent bi = new Intent(COUNTDOWN_BR);
CountDownTimer cdt = null;
public void OnCreate(){
super.onCreate();
Log.i(TAG, "starting timer...");
cdt = new CountDownTimer(30000,1000) {
#Override
public void onTick(long millisUntilFinished){
Log.i(TAG, "Countdown seconds remaining: " +millisUntilFinished /1000);
bi.putExtra("countdown", millisUntilFinished);
sendBroadcast(bi);
}
#Override
public void onFinish(){
Log.i(TAG, "Timer finished");
}
};
cdt.start();
}
#Override
public void onDestroy() {
cdt.cancel();
Log.i(TAG, "Timer cancelled");
super.onDestroy();
}
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
return super.onStartCommand(intent, flags, startId);
}
#Override
public IBinder onBind(Intent arg0) {
return null;
}
}

https://github.com/greenrobot/EventBus
Check this out. This library is the best and easiest implementation of broadcasts. You can send any data to any object (StartFast service in your case) from any other object (StartFast activity in your case) and write code to run.

First, you need to start the service and register it in the manifest. After the service is started by an activity, it will keep running in the background.
You can send intents with a service and anybody who has registered a broadcast receiver listening to that intent can hear it.
Let's say FirstActivity started the service and registers receiver listening to intent with the tag BOBBY. The service is the one sending an intent BOBBY to anyone who is interested and has registered for it.
You want to move on to SecondActivity. Before you do that, onPause of FirstActivity you need to unregister that broadcastreceiver.
SecondActivity is interested in the intent with tag BOBBY, so he creates his own broadcast receiver and registers for it.
I hope you can see where this is going.A broadcastreceiver can listen to all sorts of intents that you make up.
Have fun.

Android - Call a function from outside an activity (through AlarmManager and Notification)

Ok, so I have a main activity called 'Main.java'. This main activity starts an AlarmManager which fires an intent leading to 'AlarmReceiver.java'.
This 'AlarmReceiver.java' then creates a notification which has two buttons on it. One of the buttons is a deletion button, and so when the user clicks on that button, another intent is fired, leading it to 'DelPair.java'.
In DelPair.java, I modify a table in a Database, but then I need the UI of Main.java to reflect this change. I have created two functions in Main.java called updateArrayFromDB() and updateUIFromArray() to do this for me:
updateArrayFromDB() will sync an ArrayList created in Main.java to a
certain table in the DB.
updateUIFromArray() will change the UI of
Main.java to represent the ArrayList that has just been changed.
The problem is that I cannot call these two functions from DelPair.java (they don't exist in that space). I have come across Serializables in trying to find an answer but I don't know enough to know if they apply here or exactly how to implement them across the AlarmManager and the NotificationManager.
How can I access these methods from DelPair.java?
In Main.java:
public void updateArrayFromDB(){
//... The code for this is long and irrelevant
}
public void updateUIFromArray(){
//... The code for this is long and irrelevant
}
private void SendNotification() {
Intent intent = new Intent(this, AlarmReceiver.class);
//...
PendingIntent sender = PendingIntent.getBroadcast(this, 2 , intent, PendingIntent.FLAG_UPDATE_CURRENT);
AlarmManager am = (AlarmManager) getSystemService(ALARM_SERVICE);
am.setRepeating(AlarmManager.RTC_WAKEUP, 5000, notif_freq, sender);
}
In AlarmReceiver.java:
Intent delPairI = new Intent(context, DelPair.class);
PendingIntent delPairPI = PendingIntent.getService(context, 0, delPairI, PendingIntent.FLAG_UPDATE_CURRENT);
Notification noti;
noti = new Notification.Builder(context)
//...
.addAction(R.drawable.ic_delete_icon, "Delete the thing", delPairPI)
.build();
NotificationManager notificationManager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);
notificationManager.notify(0, noti);
and then in DelPair.java:
public class DelPair extends IntentService {
//...
#Override
protected void onHandleIntent(final Intent intent) {
//...
Intent it = new Intent(Intent.ACTION_CLOSE_SYSTEM_DIALOGS);
getApplicationContext().sendBroadcast(it);
handler.post(new Runnable() {
#Override
public void run() {
//... here is where I update the database, which works perfectly
//now need to update the UI and array in Main.java
updateArrayFromDB(); //these lines
updateUIFromArray(); //obviously don't work
}
});
}
}

Why not use broadcasts ? in onHandleIntent just send a broadcast
Intent i = new Intent();
i.setAction(CUSTOM_INTENT);
//put relevant data in intent
getApplicationContext().sendBroadcast(i);
The broadcast receiver:
public class IncomingReceiver extends BroadcastReceiver {
private MainActivity act;
public IncomingReceiver(MainActivity main){
this.act = act;
}
#Override
public void onReceive(Context context, Intent intent) {
if (intent.getAction().equals(CUSTOM_INTENT)) {
System.out.println("GOT THE INTENT");
// call the method on act
}
}
}
In your activity onResume - register new IncomingReceiver, onPause unregister
private IncomingReceiver receiver;
public void onCreate(Bundle bOs){
//other codes
receiver = new IncomingReceiver(this);
}
#Override
protected void onResume() {
IntentFilter filter = new IntentFilter();
filter.addAction(CUSTOM_INTENT);
registerReceiver(receiver, filter);
super.onResume();
}
#Override
protected void onPause() {
unregisterReceiver(receiver);
super.onPause();
}

Since you need to have an updated UI based on database changes, you can call updateArrayFromDB() and updateUIFromArray() in the onResume() method of your activity so the UI gets updated each time the user enters the activity.

Displaying Notification after Background Process done Android

I am loading an HTTP request in the background using loopj HTTP CLIENT and when it is done, I want to display a "success" notification (dialog, toast, etc.)
I have the code in a seperate (non-activity) class with a static method that executes the background request. In the end, the response is in a AsyncHttpResponseHandler under a onSuccess method. In this method, I can print out the response, confirm that the request went through, save data to the sd card/ Shared Preferences, but how do I access the UI thread to display a notification?
Thanks in advance.

you can do it using a Handler, or by calling Activity.runOnUiThread(). so you either pass a Handler, or an Activity object to your static method, then in your onSuccess() method, do,
activity.runOnUiThread(new Runnable() {
#Override
public void run() {
// i'm on the UI thread!
}
}
);
or,
handler.post(new Runnable() {
#Override
public void run() {
// i'm on the UI thread!
}
}
);

I guess you mean a service as a background process. Service has many built in methods like onCreate, onStartCommand, onDestroy, etc. I suggest using a Notification, because notifications do not require a UI thread to do the job.
Create a method to generate a notification and call it after your HTML read is over.
private static void generateNotification(Context context, String message) {
int icon = R.drawable.ic_stat_gcm;
long when = System.currentTimeMillis();
NotificationManager notificationManager = (NotificationManager)context.getSystemService(Context.NOTIFICATION_SERVICE);
Notification notification = new Notification(icon, message, when);
String title = context.getString(R.string.app_name);
Intent notificationIntent = new Intent(context, MainActivity.class);
// set intent so it does not start a new activity
notificationIntent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_SINGLE_TOP);
PendingIntent intent = PendingIntent.getActivity(context, 0, notificationIntent, 0);
notification.setLatestEventInfo(context, title, message, intent);
notification.flags |= Notification.FLAG_AUTO_CANCEL;
notificationManager.notify(0, notification);
}

You could fire a local broadcast with the message, and show a toast with a receiver.
Do this in the class doing the updates:
Intent intent = new Intent("ACTION_TOAST");
intent.putExtra("message", "Success!");
LocalBroadcastManager.getInstance(context).sendBroadcast(intent);
Then in any activity that might want to know about the update, do this:
BroadcastReceiver receiver = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent) {
if ("ACTION_TOAST".equals(intent.getAction()) {
Toast.makeText(MyActivity.this, intent.getStringExtra("message"),
Toast.LENGTH_SHORT).show();
}
}
}
#Override
protected void onStart() {
super.onStart();
LocalBroadcastManager.getInstance(this).registerReceiver(
receiver, new IntentFilter("ACTION_TOAST"));
}
#Override
protected void onStop() {
LocalBroadcastManager.getInstance(this).unregisterReceiver(receiver);
}
You still need to pass a context into your static method, but this works even if that context is a Service or some other context that can't show Toasts / create UI.

AlarmManager/BroadcastReceiver not working

I've been trying to setup my first alarm using AlarmManager and BroadCastReceiver as explained here: http://smartandroidians.blogspot.com.es/2010/04/alarmmanager-and-notification-in.html
My setup:
AndroidManifest.xml:
<receiver android:name="es.radiopodcastellano.player.SleepAlarm" />
My main Activity onCreate (this code actually resides on a subclass, but to simplify I put it there):
#Override
public void onCreate(Bundle savedInstanceState) {
// <Stripped code>
AlarmManager alarm = (AlarmManager) currentContext.getSystemService(Context.ALARM_SERVICE);
Intent intent = new Intent(this.getApplicationContext(), SleepAlarm.class);
PendingIntent pendingIntent = PendingIntent.getBroadcast(this.getApplicationContext(), 0, intent, PendingIntent.FLAG_ONE_SHOT);
alarm.set(AlarmManager.RTC_WAKEUP,(System.currentTimeMillis() + (5 * 1000)),pendingIntent);
}
SleepAlarm.java:
public class SleepAlarm extends BroadcastReceiver {
#Override
public void onReceive(Context context, Intent intent) {
Log.d("RPod_SleepAlarm","Alarm!!");
}
}
Output from "adb shell dumpsys alarm" show this, so it seems the intent is being called:
es.radiopodcastellano.player
221ms running, 32 wakeups
44 alarms: flg=0x4 cmp=es.radiopodcastellano.player/.SleepAlarm
However, Logcat shows nothing for "RPod_SleepAlarm" tag. What could I be doing wrong?

I found the problem.
The receiver on the manifest was inside another receiver for a widget, and it must be a children of the application. So, if you're having the same behaviour as me, please check that you've set up the AndroidManifest.xml correctly: