Android - AlarmManager 设置闹钟之间的随机延迟

Question

我想每 x 小时运行一次代码，但我也想在代码被触发的时间之间保持一些随机性。

我通过设置和取消一些随机延迟来尝试使用 AlarmManager，但我没有设法让它工作。

关于如何做到这一点的任何想法？

Answer 1

在你的 manifest.xml 中添加这个

<receiver android:name=".BroadcastReceiverAux" />

根据 developer.android

   Note: Beginning with API 19 (KITKAT) alarm delivery is inexact: the OS will shift alarms in order to minimize wakeups and battery use. 
There are new APIs to support applications which need strict delivery guarantees; see setWindow(int, long, long, PendingIntent) and setExact(int, long, PendingIntent). 
Applications whose targetSdkVersion is earlier than API 19 will continue to see the previous behavior in which all alarms are delivered exactly when requested.

来自https://developer.android.com/reference/android/app/AlarmManager.html#setExact(int, long, android.app.PendingIntent)

Answer 2

我设法找到了这样做的方法。我正在分享代码，以防你也需要它。

AndroidManifest.xml：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.tribta.test">

    <uses-permission android:name="android.permission.WAKE_LOCK"/>
    <uses-permission android:name="android.permission.VIBRATE"/>
    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="test"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <receiver android:process=":remote" android:name=".Alarm"></receiver>
        <service
            android:name=".MyService"
            android:enabled="true"
            android:process=":my_service" >
        </service>
    </application>
</manifest>

MainActivity.java：

package com.tribta.test;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState){

        super.onCreate(savedInstanceState);
        Intent serviceIntent = new Intent(this,MyService.class);
        this.startService(serviceIntent);
    }

    @Override
    public void onDestroy(){
        super.onDestroy();
    }
}

MyService.java：

package com.tribta.test;

import android.app.Service;
import android.content.Intent;
import android.os.IBinder;

public class MyService extends Service
{
    Alarm alarm = new Alarm();
    public void onCreate()
    {
        super.onCreate();
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId)
    {
        alarm.setAlarm(this);
        return START_STICKY;
    }

    @Override
    public void onStart(Intent intent, int startId)
    {
        alarm.setAlarm(this);
    }

    @Override
    public IBinder onBind(Intent intent)
    {
        return null;
    }
}

Alarm.java，您可以在其中放置您的代码：

package com.tribta.test;

import android.app.AlarmManager;
import android.app.PendingIntent;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.os.PowerManager;
import android.os.Vibrator;
import android.widget.Toast;

import java.util.Random;

public class Alarm extends BroadcastReceiver
{
    @Override
    public void onReceive(Context context, Intent intent)
    {
        PowerManager pm = (PowerManager) context.getSystemService(Context.POWER_SERVICE);
        PowerManager.WakeLock wl = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "");
        wl.acquire();

        // Put here YOUR code.
        Toast.makeText(context, "Alarm !!!!!!!!!!", Toast.LENGTH_LONG).show(); // For example

        Vibrator v = (Vibrator) context.getSystemService(Context.VIBRATOR_SERVICE);
        v.vibrate(300); // Vibrate for 300 milliseconds

        cancelAlarm(context);
        setAlarm(context);

        wl.release();
    }

    public void setAlarm(Context context)
    {
        AlarmManager am =( AlarmManager)context.getSystemService(Context.ALARM_SERVICE);
        Intent i = new Intent(context, Alarm.class);
        PendingIntent pi = PendingIntent.getBroadcast(context, 0, i, 0);

        Random r = new Random();
        int ri = r.nextInt(7 - 1) + 1; // random integer between 7 (inclusive) and 1 (exclusive),
        int delay = 1000 * 60 * 60 * ri; // Millisec * Second * Minute * hours

        am.set(AlarmManager.RTC_WAKEUP, System.currentTimeMillis() + delay, pi);
    }

    public void cancelAlarm(Context context)
    {
        Intent intent = new Intent(context, Alarm.class);
        PendingIntent sender = PendingIntent.getBroadcast(context, 0, intent, 0);
        AlarmManager alarmManager = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE);
        alarmManager.cancel(sender);
    }
}