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基本上大家都知道提高service优先级可以在很大程度上让你的service免于因为内存不足而被kill，当然系统只是在此时先把优先级低的kill掉，如果内存还是不够，也会把你的service干掉的。不过现在的机器不像几年前了，基本上不会发生那种情况。

先来看看网上常见的错误方法：

1.android:persistent="true"

对第三方app无效，下面是官方说明

android:persistent

Whether or not the application should remain running at all times — "true" if it should, and "false" if not. The default value is "false". Applications should not normally set this flag; persistence mode is intended only for certain system applications.

 

2.onDestroy中重启service

service被系统杀死的时候并不一定会执行onDestroy，拿什么重启

 

3.android:priority

service根本没有这属性

 

4.setForeground

这个是有效的，但是网上的例子却都是无效的原因是参数错误

 

让service免于非难的办法是提高它的重要性，在官方文档中已经说明进程有五个级别，其中前台进程最重要，所以最后被杀死。

如何使之变成前台进程可以参阅官方文档。

http://developer.android.com/guide/components/processes-and-threads.html

http://su1216.iteye.com/blog/1591699

 

这里只说如何使用setForeground将service设置为前台进程

Notification notification = new Notification();
notification.flags = Notification.FLAG_ONGOING_EVENT;
notification.flags |= Notification.FLAG_NO_CLEAR;
notification.flags |= Notification.FLAG_FOREGROUND_SERVICE;
service.startForeground(1, notification);

上面的三个属性放到一起，值为0x62。

    /**
     * Bit to be bitwise-ored into the {@link #flags} field that should be
     * set if this notification is in reference to something that is ongoing,
     * like a phone call.  It should not be set if this notification is in
     * reference to something that happened at a particular point in time,
     * like a missed phone call.
     */
    public static final int FLAG_ONGOING_EVENT      = 0x00000002;
    /**
     * Bit to be bitwise-ored into the {@link #flags} field that should be
     * set if the notification should not be canceled when the user clicks
     * the Clear all button.
     */
    public static final int FLAG_NO_CLEAR           = 0x00000020;

    /**
     * Bit to be bitwise-ored into the {@link #flags} field that should be
     * set if this notification represents a currently running service.  This
     * will normally be set for you by {@link Service#startForeground}.
     */
    public static final int FLAG_FOREGROUND_SERVICE = 0x00000040;

最后，我们可以使用下面命令看看手机中的哪些应用这么干了，你在平时使用的时候是不是他们存活时间最长，最不容易被系统干掉

dumpsys notification

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本人blog地址

http://su1216.iteye.com/

http://blog.csdn.net/su1216/