Android进程保活·双进程拉活(Java层)

Android进程

其它文章

1. 前台进程 (Foreground process)
2. 可见进程 (Visible process)
3. 服务进程 (Service process)
4. 后台进程 (Background process)
5. 空进程 (Empty process)

下面进行解释：

前台进程(Foreground process):

• 托管用户正在交互的 Activity（已调用 Activity 的 onResume() 方法）
• 托管某个 Service，后者绑定到用户正在交互的 Activity
• 托管正在“前台”运行的 Service（服务已调用 startForeground()）
• 托管正执行一个生命周期回调的 Service（onCreate()、onStart() 或 onDestroy()）
• 托管正执行其 onReceive() 方法的 BroadcastReceiver

可见进程 (Visible process):

• 托管不在前台、但仍对用户可见的 Activity（已调用其 onPause() 方法）。例如，如果前台 Activity 启动了一个对话框，允许在其后显示上一 Activity，则有可能会发生这种情况。
• 托管绑定到可见（或前台）Activity 的 Service。

可见进程被视为是极其重要的进程，除非为了维持所有前台进程同时运行而必须终止，否则系统不会终止这些进程。

服务进程 (Service process):

后台进程 (Service process):

空进程 (Empty process):

进程优先级:

Android进程保活

• 红色部分是容易被回收的进程，属于android进程
• 绿色部分是较难被回收的进程，属于android进程
• 其他部分则不是android进程，也不会被系统回收，一般是ROM自带的app和服务才能拥有

本篇文章介绍的是进程第三种方式:

• 双进程拉活(Java层)

双进程拉活(Java层):

首先创建LocalService.java继承自Service(android.app.Service):↓

public class LocalService extends Service {
    @Override
    public IBinder onBind(Intent intent) {
        return new LocalBinder();
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        /*第一个参数Intent
        第二个参数ServiceConnection*/

        /**
         *  第三个参数介绍：
        * Flag for {@link #bindService}: automatically create the service as long
        * as the binding exists.  Note that while this will create the service,
        * its {@link android.app.Service#onStartCommand}
        * method will still only be called due to an
        * explicit call to {@link #startService}.  Even without that, though,
        * this still provides you with access to the service object while the
        * service is created.
        *
        * <p>Note that prior to {@link android.os.Build.VERSION_CODES#ICE_CREAM_SANDWICH},
        * not supplying this flag would also impact how important the system
        * consider's the target service's process to be.  When set, the only way
        * for it to be raised was by binding from a service in which case it will
        * only be important when that activity is in the foreground.  Now to
        * achieve this behavior you must explicitly supply the new flag
        * {@link #BIND_ADJUST_WITH_ACTIVITY}.  For compatibility, old applications
        * that don't specify {@link #BIND_AUTO_CREATE} will automatically have
        * the flags {@link #BIND_WAIVE_PRIORITY} and
        * {@link #BIND_ADJUST_WITH_ACTIVITY} set for them in order to achieve
        * the same result.
        */
        bindService(new Intent(this,RemoteService.class),connection,Context.BIND_AUTO_CREATE);
        return super.onStartCommand(intent, flags, startId);
    }

    private ServiceConnection connection = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            //绑定成功
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {
            //当RemoteService所处进程被干掉就重新启动
            startService(new Intent(LocalService.this,RemoteService.class));
            bindService(new Intent(LocalService.this,RemoteService.class),connection,Context.BIND_IMPORTANT);
        }
    };

    private class LocalBinder extends Binder {

    }
}

<service android:name=".LocalService" />

public class RemoteService extends Service {
    public RemoteService() {
    
    }

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

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {

        /*第一个参数Intent
        第二个参数ServiceConnection
        第三个参数介绍：

        /**
        * Flag for {@link #bindService}: automatically create the service as long
        * as the binding exists.  Note that while this will create the service,
        * its {@link android.app.Service#onStartCommand}
        * method will still only be called due to an
        * explicit call to {@link #startService}.  Even without that, though,
        * this still provides you with access to the service object while the
        * service is created.
        *
        * <p>Note that prior to {@link android.os.Build.VERSION_CODES#ICE_CREAM_SANDWICH},
        * not supplying this flag would also impact how important the system
        * consider's the target service's process to be.  When set, the only way
        * for it to be raised was by binding from a service in which case it will
        * only be important when that activity is in the foreground.  Now to
        * achieve this behavior you must explicitly supply the new flag
        * {@link #BIND_ADJUST_WITH_ACTIVITY}.  For compatibility, old applications
        * that don't specify {@link #BIND_AUTO_CREATE} will automatically have
        * the flags {@link #BIND_WAIVE_PRIORITY} and
        * {@link #BIND_ADJUST_WITH_ACTIVITY} set for them in order to achieve
        * the same result.
        */
        bindService(new Intent(this,RemoteService.class),connection,Context.BIND_AUTO_CREATE);
        return super.onStartCommand(intent, flags, startId);
    }

    private ServiceConnection connection = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            //绑定成功
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {
            //当RemoteService所处进程被干掉就重新启动
            startService(new Intent(RemoteService.this,LocalService.class));
            bindService(new Intent(RemoteService.this,LocalService.class),connection,Context.BIND_IMPORTANT);
        }
    };

    private class RemoteBinder extends Binder{
    
    }
}

<service
            android:name=".RemoteService"
            android:enabled="true"
            android:exported="true"
            android:process=":remote" />
        <!--
            android:process=":remote"
            指定进程名
        -->

最后在MainActivity启动其中一个服务LocalService:

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        //双进程拉活(Java层)
        startService(new Intent(this,LocalService.class));
    }
}

这样就完成了双进程拉活