老婆保佑，代码无BUG

前言

项目中遇到一个需求，需要竟可能的上传用户的定位信息，引发了我对目前已知的保活手段的探究，同时也遇到过客户说，推送不能收到，不能像微信那样，MMP的，不想理客户

目录

• 一：如何创建前台服务
  • 1.DeskService 前台服务
  • 2.移除前台Service通知栏标志
  • 3.注册服务
  • 4.启动服务
• 二：查看adj级别

一：如何创建前台服务

1.DeskService 前台服务

package com.cpsc.livedemo;

import android.app.Notification;
import android.app.NotificationManager;
import android.app.Service;
import android.content.Intent;
import android.os.Build;
import android.os.IBinder;
import android.support.annotation.Nullable;
import android.util.Log;

/**
 * 描述:
 * <p>
 * Created by allens on 2018/1/31.
 */

public class DeskService extends Service {

    private static final String TAG = "DaemonService";
    public static final int NOTICE_ID = 100;

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

    @Override
    public void onCreate() {
        super.onCreate();
        Log.d(TAG, "DaemonService---->onCreate被调用，启动前台service");
        //如果API大于18，需要弹出一个可见通知
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR2) {
            Notification.Builder builder = new Notification.Builder(this);
            builder.setSmallIcon(R.mipmap.ic_launcher);
            builder.setContentTitle("KeepAppAlive");
            builder.setContentText("DaemonService is runing...");
            startForeground(NOTICE_ID, builder.build());
            // 如果觉得常驻通知栏体验不好
            // 可以通过启动CancelNoticeService，将通知移除，oom_adj值不变
            Intent intent = new Intent(this, CancelNoticeService.class);
            startService(intent);
        } else {
            startForeground(NOTICE_ID, new Notification());
        }
    }


    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        // 如果Service被终止
        // 当资源允许情况下，重启service
        return START_STICKY;
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        // 如果Service被杀死，干掉通知
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR2) {
            NotificationManager mManager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
            mManager.cancel(NOTICE_ID);
        }
        Log.d(TAG, "DaemonService---->onDestroy，前台service被杀死");
        // 重启自己
        Intent intent = new Intent(getApplicationContext(), DeskService.class);
        startService(intent);
    }

}

2.移除前台Service通知栏标志

package com.cpsc.livedemo;

import android.app.Notification;
import android.app.NotificationManager;
import android.app.Service;
import android.content.Intent;
import android.os.Build;
import android.os.IBinder;
import android.os.SystemClock;
import android.support.annotation.Nullable;

/**
 * 描述:
 * <p>
 * Created by allens on 2018/1/31.
 */

public class CancelNoticeService extends Service {
    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        if (Build.VERSION.SDK_INT > Build.VERSION_CODES.JELLY_BEAN_MR2) {
            Notification.Builder builder = new Notification.Builder(this);
            builder.setSmallIcon(R.mipmap.ic_launcher);
            startForeground(DeskService.NOTICE_ID, builder.build());
            // 开启一条线程，去移除DaemonService弹出的通知
            new Thread(new Runnable() {
                @Override
                public void run() {
                    // 延迟1s
                    SystemClock.sleep(1000);
                    // 取消CancelNoticeService的前台
                    stopForeground(true);
                    // 移除DaemonService弹出的通知
                    NotificationManager manager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
                    manager.cancel(DeskService.NOTICE_ID);
                    // 任务完成，终止自己
                    stopSelf();
                }
            }).start();
        }
        return super.onStartCommand(intent, flags, startId);
    }
}

3.注册服务

        <service
            android:name=".DeskService"
            android:enabled="true"
            android:exported="true"
            android:process=":daemon_service" />


        <service
            android:name=".CancelNoticeService"
            android:enabled="true"
            android:exported="true"
            android:process=":service" />

4.启动服务

 startService(new Intent(this, DeskService.class));

二：查看adj级别

adb shell

ps|grep <package_name> 查看基本信息

1|root@generic_x86:/ # ps|grep com.cpsc.livedemo                               
u0_a63    6834  1348  1285208 43884 SyS_epoll_ b73712b5 S com.cpsc.livedemo
u0_a63    6884  1348  1271160 28944 SyS_epoll_ b73712b5 S com.cpsc.livedemo:daemon_service

cat /proc/<进程id>/oom_adj

root@generic_x86:/ # cat /proc/6884/oom_adj                                    
1
root@generic_x86:/ # cat /proc/6884/oom_adj                                    
1
root@generic_x86:/ # 

参考作者链接