How do I get an android service to work when phone is idle / dozing / locked

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Java

Android

Good evening,

I've been trying to achieve something for several days now and I literally don't know what else to try, I've basically tried everything I found online and it still doesn't work but I have the feeling that once I find the solution it must be something quite simple.

I'm working on a bigger project, but here I'm just trying to get a very simple example to work which I can later adapt to my project.

What I want to do

I want to have a counter add +1 every second for 1200 seconds (20 minutes) and write to a file every time it counts. I should end up with a file with 1200 lines with a timestamp per sample.

How I'm trying to do it

I've tried a million things, but here, I've just gone back to a very basic example so I can showcase it and ask for help:

- I have a MAIN acticity with a single START button.
- When clicking the button I start a new process from the activity. This is a FOREGROUND process.
- I start counting in a loop. When I reach 1200, the counting stops.

My problem

While the phone screen is ON everything works just fine, but as soon as I lock the screen and put my phone in my pocket, depending on the phone I'm testing on, it starts to fail.

What I would like

If someone could tell me what to modify / add / change or even do it for me and write back here (it's a really simple project) I would be extremely grateful, I'm wasting a ton of time and I just can't seem to hit the right key.

I know I might be asking a bit too much but I'm quite desperate at this point. I'd be really greatful if someone could come up with a working solution.

Thank you very much.

What I have tried:

Since it's a very simple project I will just copy the 4 parts it consists of right here:

XML activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
    <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        xmlns:tools="http://schemas.android.com/tools"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".MainActivity">
    
        <Button
            android:id="@+id/start_button"
            android:layout_width="150dp"
            android:layout_height="50dp"
            android:layout_marginStart="52dp"
            android:layout_marginBottom="116dp"
            android:onClick="startProcess"
            android:text="@string/button_label_start"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintStart_toStartOf="parent" />
    
        <TextView
            android:id="@+id/counter_textView"
            android:layout_width="383dp"
            android:layout_height="412dp"
            android:gravity="center_horizontal|center_vertical"
            android:text="@string/counter_label_value"
            android:textSize="160sp"
            android:textStyle="bold"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintHorizontal_bias="0.428"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintVertical_bias="0.169" />
    
    </androidx.constraintlayout.widget.ConstraintLayout>

MANIFEST AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
    <manifest xmlns:android="http://schemas.android.com/apk/res/android"
        package="com.example.helloworld">
    
        <uses-permission android:name="android.permission.FOREGROUND_SERVICE" />
    
        <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">
    
            <service
                android:name=".ForegroundService"
                android:enabled="true"
                android:exported="true"
                android:process=":externalProcess">
            </service>
    
            <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>

MAIN MainActivity.java

package com.example.helloworld;
    
    import androidx.annotation.Nullable;
    import androidx.appcompat.app.AppCompatActivity;
    import androidx.core.content.ContextCompat;
    
    import android.app.PendingIntent;
    import android.content.Intent;
    import android.os.Bundle;
    import android.view.View;
    import android.widget.TextView;
    
    public class MainActivity extends AppCompatActivity {
    
        public static final String CHANNEL_ID = "ForegroundServiceChannel";
        private TextView mShowCount;
    
        @Override
        protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
            super.onActivityResult(requestCode, resultCode, data);
    
            int mCount = data.getIntExtra(ForegroundService.FOREGROUND_MESSAGE, -1);
            if(mShowCount != null)
                mShowCount.setText(Integer.toString(mCount));
        }
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            mShowCount = findViewById(R.id.counter_textView);
        }
    
        @Override
        protected void onResume() {
            super.onResume();
        }
    
        @Override
        protected void onStart() {
            super.onStart();
        }
    
        @Override
        protected void onPause() {
            super.onPause();
        }
    
        @Override
        protected void onStop() {
            super.onStop();
        }
    
        @Override
        protected void onDestroy() {
            super.onDestroy();
        }
    
        @Override
        protected void onRestart() {
            super.onRestart();
        }
    
        public void startProcess(View view) {
            PendingIntent pendingResult = createPendingResult(100, new Intent(), 0);
            Intent serviceIntent = new Intent(this, ForegroundService.class);
            serviceIntent.putExtra("pendingIntent", pendingResult);
            ContextCompat.startForegroundService(this, serviceIntent);
        }
    
        public void stopProcess(View view) {
            Intent serviceIntent = new Intent(this, ForegroundService.class);
            stopService(serviceIntent);
        }
    }

FOREGROUND SERVICE ForegroundService.java

package com.example.helloworld;
    
    import android.app.Notification;
    import android.app.NotificationChannel;
    import android.app.NotificationManager;
    import android.app.PendingIntent;
    import android.app.Service;
    import android.content.Intent;
    import android.os.Build;
    import android.os.IBinder;
    import android.os.SystemClock;
    import android.util.Log;
    import androidx.core.app.NotificationCompat;
    
    import java.io.File;
    import java.io.FileWriter;
    import java.util.Date;
    
    public class ForegroundService extends Service {
    
        public static final String CHANNEL_ID = "ForegroundServiceChannel";
        public static final String FOREGROUND_MESSAGE = "com.example.helloworld.FOREGROUND_MESSAGE";
    
        private PendingIntent data;
        private int mCount;
        private File basePath;
    
        public ForegroundService() {
        }
    
        @Override
        protected void finalize() throws Throwable {
            super.finalize();
        }
    
        @Override
        public void onCreate() {
            super.onCreate();
        }
    
        @Override
        public boolean stopService(Intent name) {
            return super.stopService(name);
        }
    
        @Override
        public int onStartCommand(Intent intent, int flags, int startId) {
            String input = intent.getStringExtra("inputExtra");
    
            createNotificationChannel();
            Intent notificationIntent = new Intent(this, MainActivity.class);
            PendingIntent pendingIntent = PendingIntent.getActivity(this,
                    0, notificationIntent, 0);
            Notification notification = new NotificationCompat.Builder(this, MainActivity.CHANNEL_ID)
                    .setContentTitle("Foreground Service")
                    .setContentText(input)
                    .setContentIntent(pendingIntent)
                    .build();
    
            startForeground(1, notification);
            data = intent.getParcelableExtra("pendingIntent");
            this.basePath = this.getExternalFilesDir("recs");
    
            mCount = 0;
            new Thread(new Runnable() {
                public void run() {
                    try {
                        while(mCount < 1200) {
                            Intent resultIntent = new Intent();
                            resultIntent.putExtra(FOREGROUND_MESSAGE, ++mCount);
                            writeFile((new Date().getTime() / 1000) + " Increasing counter: " + mCount + "\n");
                            data.send(ForegroundService.this, 200, resultIntent);
                            SystemClock.sleep(1000);
                        }
                    }catch (Exception ignored){}
                }
            }).start();
    
            //stopSelf();
            return START_NOT_STICKY;
        }
    
        private void createNotificationChannel() {
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
                NotificationChannel serviceChannel = new NotificationChannel(
                        CHANNEL_ID,
                        "Foreground Service Channel",
                        NotificationManager.IMPORTANCE_DEFAULT
                );
                NotificationManager manager = getSystemService(NotificationManager.class);
                manager.createNotificationChannel(serviceChannel);
            }
        }
    
        @Override
        public void onDestroy(){
            super.onDestroy();
        }
    
        @Override
        public IBinder onBind(Intent intent) {
            return null;
        }
    
        private void writeFile(String data)
        {
            File file = new File (basePath,"test");
            if (!file.exists()) {
                boolean mkdirs = file.mkdirs();
                if (!mkdirs) {
                    Log.e("RECORDING", "Error creating SAVE BASE PATH");
                }
            }
    
            try{
                File counter_file = new File(file, "counter.txt");
                FileWriter writer = new FileWriter(counter_file, true);
                writer.append(data);
                writer.flush();
                writer.close();
            } catch (Exception e){
                e.printStackTrace();
            }
        }
    }