How to perfectly sync clock app widget with system clock in Android?

问题

I made a digital clock widget which is using AlarmManager to update the time every 60 seconds.

@Override
public void onEnabled(Context context) {
    super.onEnabled(context);
    Log.d("onEnabled","Widget Provider enabled.  Starting timer to update widget every minute");
    AlarmManager alarmManager = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE);
    alarmManager.setRepeating(AlarmManager.RTC, System.currentTimeMillis(), 60000, createClockTickIntent(context));
}

The problem is, polling the system time every 60 seconds does not sync my widget time with system time. lets say user adds widget at 6:00:20, my widget shows the time 6:00 and sleeps for 60 seconds, so when system time becomes 6:01:00, my widget needs another 20 seconds to catch up.

Is there a way to do the following ?

• step 1: get system time and show on widget.

• step 2: set the first update interval = (60 - current Seconds value).

• step 3: after first update, set the subsequent update intervals to 60 seconds.

回答1:

Intercept the ACTION_TIME_TICK broadcast. This broadcast action is sent on every minute change of the local time zone clock.

private BroadcastReceiver receiver;

@Override
public void onEnabled(Context context)
{
    super.onEnabled();
    receiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context ctx, Intent intent)
        {
            if (intent.getAction().compareTo(Intent.ACTION_TIME_TICK) == 0) {
                // update widget time here using System.currentTimeMillis()
            }
        }
    };

    context.getApplicationContext().registerReceiver(receiver, new IntentFilter(Intent.ACTION_TIME_TICK));
}

@Override
public void onDisabled(Context context)
{
    super.onDisabled();
    if (receiver != null)
        context.getApplicationContext().unregisterReceiver(receiver);
}

Further considerations:

• We could have tried catching the ACTION_TIME_TICK broadcast in the AppWidgetProvider class' onReceive() method (after adding the action to the intent-filter in the manifest) but the documentation states that this broadcast action can only be intercepted by a BroadcastReceiver registered programmatically. Still, this may be worth a try.
• It is not that using a BroadcastReceiver is "better" than using the AlarmManager. Different approaches are required in different situations, and since the ACTION_TIME_TICK broadcast is sent by the system, why not exploit that ?

回答2:

This is an old question but using BroadcastReceiver with ACTION_TIME_TICK on Android Oreo and above won't work anymore. An better alternative for API Level 17+ would be to use TextClock which is supported by RemoteViews. Just add something like this in your clock widget layout:

<TextClock
        android:id="@+id/widget_clock"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="56sp"
        tools:text="12:45"
        <!-- You can also easily add custom typefaces -->
        android:fontFamily="@font/quicksand_regular"
        android:textColor="@color/white"/>

The clock should sync automatically with the system clock.

来源：https://stackoverflow.com/questions/29345686/how-to-perfectly-sync-clock-app-widget-with-system-clock-in-android