Android5.0之后提供了JobService和JobScheduler，用于在稍后的某個(gè)時(shí)間點(diǎn)或者當(dāng)滿足某個(gè)特定的條件時(shí)執(zhí)行一個(gè)任務(wù)。使用JobScheduler，我們可以在用戶一段時(shí)間沒有使用我們的app的情況下，推送本地通知來提高app的用戶留存率。廢話不多說，上代碼：
先在app的MainActivity啟動(dòng)時(shí)用JobScheduler來schedule一個(gè)job。注意在onCreate中我們把用戶啟動(dòng)app的時(shí)間記錄在了shared preference里面：

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    sharedPreferences.edit().putLong(Constants.SP_PARAM_LAST_LAUNCH, System.currentTimeMillis()).apply();
    scheduleNotifications();
}

private void scheduleNotifications() {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            try {
                JobScheduler jobScheduler = (JobScheduler) getSystemService(JOB_SCHEDULER_SERVICE);
                JobInfo jobInfo = new JobInfo.Builder(1, new ComponentName(getPackageName(), NotificationService.class.getName()))
                        .setRequiresCharging(false)
                        .setRequiredNetworkType(JobInfo.NETWORK_TYPE_ANY) //任何有網(wǎng)絡(luò)的狀態(tài)
                        .setPersisted(true) //系統(tǒng)重啟后保留job
                        .setPeriodic(1000 * 60 * 60 * 24) //這里的單位是毫秒，1000 * 60 * 60 * 24代表一天（24小時(shí)）
                        .build();
                jobScheduler.schedule(jobInfo);
            } catch (Exception ex) {
                Log.e("scheduleNotifications failure");
            }
        }
    }

然后是推送通知的NotificationService，這里SharedPreferences是用的dagger2依賴注入，不用dagger的可以直接用PreferenceManager.getDefaultSharedPreferences來獲得:

@RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
public class NotificationService  extends JobService {
    @DefaultSharedPref
    @Inject
    SharedPreferences sharedPreferences;

    @Override
    public boolean onStartJob(JobParameters params) {
        try {
            long lastLaunchTime = sharedPreferences.getLong(Constants.SP_PARAM_LAST_LAUNCH, -1);
            if(lastLaunchTime > 0) {
                long intervalSinceLastLaunch = System.currentTimeMillis() - lastLaunchTime;
                //檢查距離用戶上一次啟動(dòng)app是否過了一定時(shí)間
                if(intervalSinceLastLaunch > 1000 * 60 * 60 * 24) {
                            NotificationCompat.Builder mBuilder =
                                    new NotificationCompat.Builder(NotificationService.this)
                                            .setAutoCancel(true)
                                            .setSmallIcon(R.mipmap.ic_launcher)
                                            .setContentTitle("我的app")
                                            .setContentText("又有新的內(nèi)容上線了，快來我們app看看吧!");
                            Intent resultIntent = new Intent(NotificationService.this, MainActivity.class);

                            TaskStackBuilder stackBuilder = TaskStackBuilder.create(NotificationService.this);
                            stackBuilder.addParentStack(MainActivity.class);
                            stackBuilder.addNextIntent(resultIntent);
                            PendingIntent resultPendingIntent =
                                    stackBuilder.getPendingIntent(
                                            0,
                                            PendingIntent.FLAG_UPDATE_CURRENT
                                    );
                            mBuilder.setContentIntent(resultPendingIntent);
                            NotificationManager mNotificationManager =
                                    (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
                            mNotificationManager.notify(1, mBuilder.build());
                }
            }
        } catch (Exception ex) {
            Log.e("Exception in NotificationService onStartJob");
        }
        return false;
    }

    @Override
    public boolean onStopJob(JobParameters params) {
        Log.d("NotificationService onStopJob");
        return true;
    }
}

最后需要在Manifest中注冊我們的service和申請相關(guān)的權(quán)限:

    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
    <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />

    <service android:name=".NotificationService"
            android:permission="android.permission.BIND_JOB_SERVICE" />