重复提醒通知Android(java)问题

Question

I created a reminder every 10 minutes 00 seconds, but notifications always come at different times... for example 5:10:32, 5:20:41, 5:32:01, 5:41:20.. instead of 5: 10:00, 5:20:00, 5:30:00, 5:40:00 Can anyone know what the problem might be?

public class MainActivity extends AppCompatActivity  implements View.OnClickListener {

    private int notificationId = 1;

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

        findViewById(R.id.setBtn).setOnClickListener(this);
        findViewById(R.id.cancelBtn).setOnClickListener(this);

    }

    @Override
    public void onClick(View v) {

        EditText editText = findViewById(R.id.editText);
        TimePicker timePicker = findViewById(R.id.timePicker);

        // Set notificationId & message
        Intent intent = new Intent(MainActivity.this, AlarmRecevier.class);
        intent.putExtra("notificationId", notificationId);
        intent.putExtra("message", editText.getText().toString());

        //PendingIntent
        PendingIntent alarmIntent = PendingIntent.getBroadcast(
                MainActivity.this, 0,intent,PendingIntent.FLAG_UPDATE_CURRENT); //FLAG_CANCEL_CURRENT
        //AlarmManager
        AlarmManager alarmManager = (AlarmManager) getSystemService(ALARM_SERVICE);

        switch (v.getId()){
            case R.id.setBtn:
                //set Alarm
                int hour = timePicker.getHour();
                int minute = timePicker.getMinute();
                // Create time
                Calendar startTime = Calendar.getInstance();
                startTime.set(Calendar.HOUR_OF_DAY, hour);
                startTime.set(Calendar.MINUTE, minute);
                startTime.set(Calendar.SECOND, 0);
                long alarmStartTime = startTime.getTimeInMillis();
                long repTime = 600000L;

                // Set Alarm Repeat
                //alarmManager.set(AlarmManager.RTC_WAKEUP, alarmStartTime, alarmIntent);
                alarmManager.setRepeating(AlarmManager.RTC_WAKEUP, alarmStartTime, repTime, alarmIntent);
                Toast.makeText(this,"Done!", Toast.LENGTH_SHORT).show();
                break;


            case R.id.cancelBtn:
                //CancelAlarm
                alarmManager.cancel(alarmIntent);
                Toast.makeText(this,"Cancelled", Toast.LENGTH_SHORT).show();
                break;
        }
    }
}

public class AlarmRecevier extends BroadcastReceiver {

    private static final String CHANNEL_ID = "SAMPLE_CHANNEL";

    @Override
    public void onReceive(Context context, Intent intent) {
        // get ID & message from Intent
        int notificationId = intent.getIntExtra("notificationId",0);
        String message = intent.getStringExtra("message");

        //Call MainActivity when notification is tapped
        Intent mainIntent = new Intent(context, MainActivity.class);
        PendingIntent contentIntent = PendingIntent.getActivity(
                context,0,mainIntent,PendingIntent.FLAG_UPDATE_CURRENT
        );

        //NotificationManager
        NotificationManager notificationManager =
                (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O){
            //For API 26 and above.
            CharSequence channel_name = "My Notification";
            int importance = NotificationManager.IMPORTANCE_DEFAULT;

            NotificationChannel channel = new NotificationChannel(CHANNEL_ID, channel_name,importance);
            notificationManager.createNotificationChannel(channel);
        }
        // prepare notification
        NotificationCompat.Builder builder = new NotificationCompat.Builder(context, CHANNEL_ID)
                .setSmallIcon(R.drawable.ic_flower)
                .setContentTitle("FLOVERS")
                .setContentText("Полей цветок")
                .setContentIntent(contentIntent)
                .setPriority(NotificationCompat.PRIORITY_DEFAULT)
                .setAutoCancel(true);

        //Notify
        notificationManager.notify(notificationId, builder.build());


    }
}

Answer 1

From the documentation of setRepeating() :

Note: as of API 19, all repeating alarms are inexact. If your application needs precise delivery times then it must use one-time exact alarms, rescheduling each time as described above. Legacy applications whose targetSdkVersion is earlier than API 19 will continue to have all of their alarms, including repeating alarms, treated as exact.

They make it difficult because they want to discourage precise alarms. Precise alarms drain batteries faster.