在Android中如何更新小部件(使用AlarmManager)

Question

我的应用程序使用一个小部件，我想在一天的特定时间更新它。下面是代码：

package com.apps.app;

import android.app.AlarmManager;
import android.app.PendingIntent;
import android.appwidget.AppWidgetManager;
import android.appwidget.AppWidgetProvider;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.util.Log;
import android.widget.RemoteViews;

import com.snappydb.DB;
import com.snappydb.DBFactory;
import com.snappydb.SnappydbException;

import java.util.ArrayList;
import java.util.Calendar;

public class Widget extends AppWidgetProvider {

public static String ACTION_AUTO_UPDATE_WIDGET = "ACTION_AUTO_UPDATE_WIDGET";

@Override
public void onReceive(Context context, Intent intent) {
    super.onReceive(context, intent);

    if (ACTION_AUTO_UPDATE_WIDGET.equals(intent.getAction())) {
        Log.d("widget","received");
        onUpdate(context, AppWidgetManager.getInstance(context),
                AppWidgetManager.getInstance(context).getAppWidgetIds(new ComponentName(context, Widget.class)));
    }
}

@Override
public void onDisabled(Context context) {
    super.onDisabled(context);
    Intent intent = new Intent(context, Widget.class);
    intent.setAction(ACTION_AUTO_UPDATE_WIDGET);
    AlarmManager alarmMgr = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE);
    alarmMgr.cancel(PendingIntent.getBroadcast(context, 0, intent, 0));
}

@Override
public void onEnabled(Context context) {
    super.onEnabled(context);

    try {
        DB db = DBFactory.open(context, "notes");
        ArrayList <Note> noteArrayList = db.getObject("notes", ArrayList.class);
        for(Note note: noteArrayList) {
            setUpdateIntent(context, note.getHours(), note.getMinutes());
        }
    } catch (SnappydbException e) {
        e.printStackTrace();
    }
    
}

private void setUpdateIntent(Context context, int h, int m) {
    Intent intent1 = new Intent(context, Widget.class);
    intent1.setAction(ACTION_AUTO_UPDATE_WIDGET);
    PendingIntent alarmIntent = PendingIntent.getBroadcast(context, h*m, intent1, 0);

    Calendar c = Calendar.getInstance();
    c.set(Calendar.HOUR_OF_DAY, h);
    c.set(Calendar.MINUTE, m);

    AlarmManager alarmMgr = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE);
    alarmMgr.setRepeating(AlarmManager.RTC, c.getTimeInMillis(), AlarmManager.INTERVAL_DAY, alarmIntent);
}

@Override
public void onUpdate(Context context, AppWidgetManager appWidgetManager, int[] appWidgetIds) {
    super.onUpdate(context, appWidgetManager, appWidgetIds);
    for (int id : appWidgetIds) {
        updateWidget(context, appWidgetManager, id);
    }
}

private void updateWidget(Context context, AppWidgetManager manager, int widgetId) {
    RemoteViews widgetView = new RemoteViews(context.getPackageName(), R.layout.widget);
    widgetView.setTextViewText(R.id.dateTextView, TimeManager.getDay());
    widgetView.setTextViewText(R.id.curTimeTextView, TimeManager.getTime());
    widgetView.setTextViewText(R.id.weatherTextView,
            context.getSharedPreferences("weather", Context.MODE_PRIVATE).getString("weather", "default"));

    Intent configIntent = new Intent(context, MainActivity.class);
    configIntent.setAction(AppWidgetManager.ACTION_APPWIDGET_CONFIGURE);
    configIntent.putExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, widgetId);
    PendingIntent pIntent = PendingIntent.getActivity(context, widgetId, configIntent, 0);
    widgetView.setOnClickPendingIntent(R.id.layoutId, pIntent);

    manager.updateAppWidget(widgetId, widgetView);
}

}

根据DB的数据，应该在17:37、17:40和17:42准确更新。这是我的更新日志：

2021-09-07 17:38:31.518 6787-6787/com.apps.app D/widget: received
2021-09-07 17:38:31.547 6787-6787/com.apps.app D/widget: received
2021-09-07 17:42:52.078 6787-6787/com.apps.app D/widget: received
2021-09-07 17:42:52.092 6787-6787/com.apps.app D/widget: received

我真的不明白小部件的更新是基于什么算法。有人能给我解释一下吗？

Answer 1

如果您的应用程序希望允许传递时间漂移，以确保警报之间总是至少有一定的时间间隔，那么需要采取的方法是使用一次警报，在处理每个警报传递时自己调度下一个警报。

从API 19开始，所有重复的警报都是不准确的。如果您的应用程序需要精确的交付时间，那么它必须使用一次精确警报，重新安排每次发送时间。其targetSdkVersion早于API 19的遗留应用程序将继续将其所有警报(包括重复警报)作为精确处理。