Android O上service保活方案

从android O版本开始，google为了控制资源使用增加了两项后台限制：

• 后台服务
• 广播

今天主要说后台服务

其中对于后台服务的限制，指的是如果应用处于后台，则不允许直接使用startService

可以使用新增的startForgroundService api启动前台服务（在调用此api之后5s之内必须调用startFroground启动前台服务通知）

那什么是后台应用？后台的对立面是前台，google对于前台的定义如下：

• 具有可见的activity（不管该activity已启动还是已暂停）
• 具有前台服务
• 有关联的前台应用（如壁纸，通知侦听器等）

具体可参考官方链接：

https://developer.android.com/about/versions/oreo/background

思路：如果app在前台的时候，service一般不会被干掉，切到后台只能存活1分钟左右就会被系统干掉，当service被干掉就会执行onDestory方法，在onDestory中启动一个1像素的activity，这个activity启动之后去重新启动下service，然后finish（不能直接在onDestory中启动service，会报错），这样就能保证service在后台长时间存活

废话不多说，直接上代码：

public class FirstService extends Service {

    private final String TAG = "FirstService";

    public static void start(Context context){
        Intent intent = new Intent(context, FirstService.class);
        AndroidOAdapter.startService(context, intent);
    }

    Handler handler = new Handler();

    int count = 0;

    Runnable runnable = new Runnable() {
        @Override
        public void run() {
            Log.d(TAG,"FirstService running "+count++);
            if (count==10) SecondService.start(FirstService.this);
            handler.postDelayed(this, 1000);
        }
    };

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


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

//        bindSecondService();

    }

//    private void bindSecondService() {
//        bindService(new Intent(this, SecondService.class), new ServiceConnection() {
//            @Override
//            public void onServiceConnected(ComponentName name, IBinder service) {
//                Log.d(TAG,"onServiceConnected ");
//                SecondService secondService = ((SecondService.LocalBinder) service).getService();
//
//                AndroidOAdapter.startForeground(secondService);
//                AndroidOAdapter.startForeground(FirstService.this);
//                secondService.stopForeground(true);
//                FirstService.this.unbindService(this);
//            }
//
//            @Override
//            public void onServiceDisconnected(ComponentName name) {
//                Log.d(TAG,"onServiceDisconnected ");
//            }
//        }, Service.BIND_AUTO_CREATE);
//    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        Log.d(TAG,"onStartCommand... ");

        return START_STICKY;
    }


    @Override
    public void onDestroy() {
        Log.d(TAG,"onDestroy....");
        handler.removeCallbacks(runnable);
        AndroidOAdapter.onServiceDestory(this);
        super.onDestroy();
    }
}

public class AndroidOServiceHelpActivity extends Activity {

    public static String EXTRA_COMPONENT_NAME = "componentName";

    public static void start(Context context, ComponentName componentName){
        Intent intent = new Intent(context, AndroidOServiceHelpActivity.class);
        intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        intent.putExtra(EXTRA_COMPONENT_NAME, componentName);
        context.startActivity(intent);
    }

    private String tag = this.getClass().getSimpleName();

    Handler handler = new Handler();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setOnePixLayout();
        Log.d(tag,"onCreate...");

        onStartService(getIntent());

    }

    @Override
    protected void onNewIntent(Intent intent) {
        onStartService(intent);
    }

    private void onStartService(Intent intent) {
        Log.d(tag,"onStartService...");
        if(intent!=null){
            ComponentName componentName = intent.getParcelableExtra(EXTRA_COMPONENT_NAME);
            if(componentName!=null){
                Intent serviceIntent = new Intent();
                serviceIntent.setComponent(componentName);
                startService(serviceIntent);
                finish();
            }
        }
        finish();
    }

    private void setOnePixLayout() {
        //设置1像素
        Window window = getWindow();
        window.setGravity(Gravity.LEFT | Gravity.TOP);
        WindowManager.LayoutParams params = window.getAttributes();
        params.x = 0;
        params.y = 0;
        params.height = 1;
        params.width = 1;
        window.setAttributes(params);
        getWindow().addFlags(WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE
                |WindowManager.LayoutParams.FLAG_WATCH_OUTSIDE_TOUCH);
    }

    @Override
    protected void onResume() {
        super.onResume();
        Log.d(tag,"onResume...");
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        Log.d(tag,"onDestroy...");
    }

    @Override
    protected void onPause() {
        super.onPause();
        Log.d(tag,"onPause...");
    }

    @Override
    protected void onStop() {
        super.onStop();
        Log.d(tag,"onStop...");
    }

//    @Override
//    public void onBackPressed() {
//
//    }
}

public class AndroidOAdapter {


    public static void onServiceDestory(Service service){
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O && BaseApplication.getAppContext().getApplicationInfo().targetSdkVersion >= 26) {
            AndroidOServiceHelpActivity.start(service, new ComponentName(service, service.getClass()));
        }
    }
}

这种方式需要后台弹出权限（小米和vivo），华为好像没有这个权限，但是小米5s上我测试了这个权限默认是给打开的