安卓开发学习笔记—————《第一行代码》第十章 服务

服务：是Android中实现程序后台运行的解决方案，适合去执行那些不需要和用户而且还要求长期运行的任务。

定义一个服务

onCreate()方法会在服务创建的时候调用

onStartCommand()方法会在每次服务启动的时候调用

onDestroy()方法会在服务销毁的时候调用

MyService.java

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

    private DownloadBinder mBinder = new DownloadBinder();

    class DownloadBinder extends Binder {

        public void startDownload() {
            Log.d("MyService","startDownload executed");
        }

        public int getProgress() {
            Log.d("MyService","getProgress executed");
            return 0;
        }
    }

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

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

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

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

启动服务

Intent startIntent = new Intent(this, MyService.class);
startService(startIntent);

停止服务

Intent stopIntent = new Intent(this, MyService.class);
stopService(stopIntent);

活动和服务进行通信

创建一个专门的Binder对象来对下载功能进行管理

修改MainActivity.java

public class MainActivity extends AppCompatActivity implements View.OnClickListener{

    private MyService.DownloadBinder downloadBinder;

    private ServiceConnection connection = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            downloadBinder = (MyService.DownloadBinder)service;
            downloadBinder.startDownload();
            downloadBinder.getProgress();
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button startService = (Button)findViewById(R.id.start_service);
        Button stopService = (Button)findViewById(R.id.stop_service);
        startService.setOnClickListener(this);
        stopService.setOnClickListener(this);
        Button bindService = (Button)findViewById(R.id.bind_service);
        Button unbindService = (Button)findViewById(R.id.unbind_service);
        bindService.setOnClickListener(this);
        unbindService.setOnClickListener(this);
        Button startIntentService = (Button)findViewById(R.id.start_intent_service);
        startIntentService.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.start_service:
                Intent startIntent = new Intent(this, MyService.class);
                startService(startIntent);
                break;
            case R.id.stop_service:
                Intent stopIntent = new Intent(this, MyService.class);
                stopService(stopIntent);
                break;
            case R.id.bind_service:
                Intent bindIntent = new Intent(this,MyService.class);
                bindService(bindIntent,connection,BIND_AUTO_CREATE);
                break;
            case R.id.unbind_service:
                unbindService(connection);
                break;
            case R.id.start_intent_service:
                Log.d("MainActivity","Thread id is " + Thread.currentThread().getId());
                Intent intentService = new Intent(this,MyIntentService.class);
                startService(intentService);
                break;
            default:
                break;
        }
    }
}

创建一个ServiceConnection匿名类，重写onServiceConnected和onServiceDisconnected方法，会在活动与服务成功绑定与断开时调用。

IntentService

服务中的代码都是默认允许在主线程中。Android专门提供了一个IntentService类，创建一个异步的，会自动停止的服务。

public class MyIntentService extends IntentService {

    public MyIntentService() {
        super("MyIntentService");
    }

    @Override
    protected void onHandleIntent(@Nullable Intent intent) {
        Log.d("MyIntentService","Thread id is" + Thread.currentThread().getId());
    }

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

启动方式

Intent intentService = new Intent(this, MyIntentService.class);
startService(intentService);