简介

Android系统的后台服务组件，适用于无界面、长时间运行的场景

特点

后台运行，没有用户界面，不可交互；
比非活动的Activity优先级高，被系统回收可能性小；
被回收后可以自动恢复；
进程间通讯

生命周期

void onCreate()

Service第一次创建时调用，只会被调用一次

int onStartCommand(Intent intent, int flags, int startId)

每次客户端调用startService时调用，可以被调用多次，startId表示被调用的次数，0开始

START_STICKY：kill后，重启，intent值为null
START_NOT_STICKY：kill后，不重启
START_REDELIVER_INTENT： kill后，重启，intent值保留
START_STICKY_COMPATIBILITY： START_STICKY的兼容版本，不一定保证能重启

IBinder onBind(Intent intent)

客户端绑定时调用，返回Ibinder对象用于通讯

boolean onUnbind(Intent intent)

解绑

void onDestroy()

Service销毁时调用

示例

public class MyService extends Service {
    private final String TAG = MyService.class.getSimpleName();
    private MyBinder mMyBinder = new MyBinder();
    public MyService() {
    }

    @Override
    public void onCreate() {
        Log.d(TAG, "onCreate");      
        super.onCreate();
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        Log.d(TAG, "onStartCommand intent:" + intent + " startId:" + startId);
        return super.onStartCommand(intent, flags, startId);
    }

    @Override
    public boolean onUnbind(Intent intent) {
        return super.onUnbind(intent);
    }

    @Override
    public IBinder onBind(Intent intent) {
        Log.d(TAG, "onBind");
        return mMyBinder;
    }

    @Override
    public void onDestroy() {
        Log.d(TAG, "onDestroy");
        super.onDestroy();
    }

    public class MyBinder extends Binder {
        public void test(String test){
            Log.d(TAG,"test - :" + test.length());
        }
    }
}

Mainfest配置

android:name: service名称，必须
android:process：进程名，默认在创建进程，可选
android:enabled：能否被系统实例化，必须
android:exported：能否被其他应用调用，必须
android:permission：权限，可选
intent-filter：意图过滤，可选

        <service
            android:name=".MyService"
            android:enabled="true"
            android:exported="true"
            android:permission="cfyushi.wzs.123">
            <intent-filter>
                <action android:name="com.cfyushi.MyService" />
            </intent-filter>
        </service>

启动和停止

startService(Intent service)

启动服务，可多次调用

stopService(Intent name)

停止服务

Intent的创建

Intent intent = new Intent(); intent.setClassName(this,“类名");

Intent intent = new Intent();intent.setAction(“intent-filter”);intent.setPackage(“应用包名");

Intent intent  = new Intent(context, xx.class)

绑定和解绑

boolean bindService(Intent service, ServiceConnection conn, int flags)

客户端调用此接口进行绑定，然后通讯交互

BIND_AUTO_CREATE：当收到绑定请求时，如果服务尚未创建，则即刻创建

BIND_DEBUG_UNBIND：调试解绑接口，仅Debug

BIND_NOT_FOREGROUND系统将阻止驻留该服务的进程具有前台优先级，仅在后台运行

ServiceConnection

private ServiceConnection mSC = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            Log.d(TAG, "onServiceConnected name:" + name);
            mBinder = (MyService.MyBinder)service;       
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {
            Log.d(TAG, "onServiceDisconnected");
            mMyService = null;
        }
    };

void unbindService(ServiceConnection conn)

解绑

IntentService

Service是在UI线程运行，不能处理耗时任务
IntentService会单独创建线程顺序执行Intent请求、执行完毕会自动停止、只需要执行onHandleIntent，其他方法（onBind、onStartCommand）默认实现

public class MyIntentService extends IntentService {
   

    private final String TAG =MyIntentService.class.getSimpleName();

    public MyIntentService() {
        super("MyIntentService");
    }
    
    @Override
    public void onCreate() {
        super.onCreate();
    }


    @Override
    public int onStartCommand(@Nullable Intent intent, int flags, int startId) {
        return super.onStartCommand(intent, flags, startId);
    }

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

    @Override
    protected void onHandleIntent(Intent intent) {
        if (intent != null) {
            //获取action和参数
            final String action = intent.getAction();
            Log.d(TAG, "onHandleIntent action:" + action);
            Log.d(TAG, "Thread:" + Thread.currentThread());
            final String param1 = intent.getStringExtra("EXTRA_PARAM1");
            final String param2 = intent.getStringExtra("EXTRA_PARAM2");
        }
    }
    
}

Aidl

支持基本类型、String、List、Map和序列化对象

创建aidl文件

以IMyAidlInterface.aidl为例

interface IMyAidlInterface {
    int test(String test);
}

配置Mainfest

     <service
            android:name=".MyAidlService"
            android:enabled="true"
            android:exported="true"
            android:process=":aidl">
            <intent-filter>
                <action android:name="com.cfyushi.MyAidlService" />
            </intent-filter>
        </service>

创建Aidl service

public class MyAidlService extends Service {

    private final String TAG = MyAidlService.class.getSimpleName();

    public MyAidlService() {
    }


    @Override
    public void onCreate() {
        Log.d(TAG, "onCreate");
        super.onCreate();
    }


    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        Log.d(TAG, "onStartCommand intent:" + intent + " startId:" + startId);
       return super.onStartCommand(intent, flags, startId);    
    }

    
    @Override
    public void onDestroy() {
        Log.d(TAG, "onDestroy");
        super.onDestroy();
    }


    @Override
    public boolean onUnbind(Intent intent) {
        return super.onUnbind(intent);
    }


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

    IMyAidlInterface.Stub mStub = new IMyAidlInterface.Stub() {

        /**
         *
         * @param test
         * @return
         * @throws RemoteException
         */
        @Override
        public int test(String test) throws RemoteException {
            String s = null;
            Log.d(TAG, "test:" + test);
            Log.d(TAG, "s:" + s.length());
            return 0;
        }
    };
}

Binder

Binder是android系统中常用的IPC通讯机制，以内核层Binder驱动为主，Client和Server以此基础进行通讯。

Paste_Image.png

Service保活

程序异常报错、系统回收等原因会导致Service停止工作，因此保活至关重要，以下措施在系统强杀和root流氓软件强杀下无效，也没必要有效，我们不做流氓。

设置为前台进程

Notification.Builder nb = new Notification.Builder(getApplication());
        Intent notificationIntent = new Intent(this, MainActivity.class);
        PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, notificationIntent, 0);
        nb.setWhen(System.currentTimeMillis());
        nb.setTicker("1111");
        nb.setContentTitle("sevrice 在前台");
        nb.setContentIntent(pendingIntent);
        startForeground(1, nb.build());

onStartCommand返回START_STICK

@Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        Log.d(TAG, "onStartCommand intent:" + intent + " startId:" + startId);
        return START_STICKY;
        //return super.onStartCommand(intent, flags, startId);
    }

native层保活

在native层创建守护线程，github地址

还有一些不推荐使用的方法，配置android:persistent=“true”、重写Service的onDestroy方法、服务互绑和监听闹钟及广播