Activity Service 컴포넌트간에 데이터 교환

Service Component

public class MainActivity extends AppCompatActivity {

  private SubService mService;
  private boolean mBound;
  Button getCountValue;
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    getCountValue = findViewById(R.id.getCountValue);

    getCountValue.setOnClickListener(new View.OnClickListener() {
      @Override
      public void onClick(View v) {
        if (mBound){
          Toast.makeText(mService, "값 : "+mService.getValue(), Toast.LENGTH_SHORT).show();
        }
      }
    });
  }

  @Override
  protected void onStart() {
    super.onStart();
    Intent intent = new Intent(this,SubService.class);
    bindService(intent, mConnection, BIND_AUTO_CREATE);
  }

  @Override
  protected void onStop() {
    super.onStop();
    if (mBound){
      unbindService(mConnection);
      mBound = false;
    }
  }

  private ServiceConnection mConnection = new ServiceConnection() {
    @Override
    public void onServiceConnected(ComponentName name, IBinder service) { 
      //서비스가 연결됬을때 서비스의 IBinder가 넘어온다
      SubService.MyBinder binder = (SubService.MyBinder) service;
      mService = binder.getService();
      mBound = true;
    }

    @Override
    public void onServiceDisconnected(ComponentName name) {
      //예기치 않은 종료시 실행되는 코드
    }
  };

}

Service Component

public class SubService extends Service {

  private  String value = "값이다.";

  private IBinder mBinder = new MyBinder();
  public class MyBinder extends Binder{
    public SubService getService(){
      return SubService.this;
    }
  }

  public SubService() {
  }

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

  public String getValue(){
    return value;
  }
}

getCountValue는 Button 이고 activity_main에 Button을 생성한후 id로 getCountValue로 지정하면된다.