android四大组件之Service

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service与activity都是从Context派生出来。
先看service的生命周期：
这里写图片描述

通过代码看service的几种形式：

1首先，最简单的形式直接启动service；

public class MyService extends Service {    public MyService() {    }    @Override    public IBinder onBind(Intent intent) {        // TODO: Return the communication channel to the service.        throw new UnsupportedOperationException("Not yet implemented");    }    @Override    public int onStartCommand(Intent intent, int flags, int startId) {        Toast.makeText(this,"myService start",Toast.LENGTH_SHORT).show();        return START_STICKY;    }}

2通过bindService（）启动service；

public class BindService extends Service {    private IBinder binder=new LocalBinder();    public BindService() {    }    public class LocalBinder extends Binder {        BindService getService(){            return BindService.this;        }    }    public IBinder onBind(Intent intent){        return binder;    }    public String getString(){        return "suceessful !!!";    }}

3通过intentService；其中intentService是运行另外一个线程，而前面的两个是运行在主线程的；

public class MyIntentService extends IntentService {    public MyIntentService() {        super("MyIntentService");    }    @Override    protected void onHandleIntent(Intent intent) {        System.out.println("IntentService start");    }}

看主测试类，这里要注意下bindService的用法；

public class MainActivity extends AppCompatActivity {    Button btnService,btnIntentService,bindService;    BindService mService;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        btnService=(Button)findViewById(R.id.service);        btnIntentService=(Button)findViewById(R.id.IntentService);        bindService=(Button)findViewById(R.id.bindService);        btnService.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                Intent intent=new Intent(getApplicationContext(),MyService.class);                startService(intent);            }        });        btnIntentService.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                Intent intent1 = new Intent(getApplicationContext(), MyIntentService.class);                startService(intent1);            }        });        bindService.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                Toast.makeText(getApplication(),mService.getString(),Toast.LENGTH_SHORT).show();            }        });    }    @Override    protected void onStart(){        super.onStart();        Intent intent = new Intent(getApplicationContext(), BindService.class);        bindService(intent, mConnection, getApplicationContext().BIND_AUTO_CREATE);    }    private ServiceConnection mConnection=new ServiceConnection() {        @Override        public void onServiceConnected(ComponentName name, IBinder service) {            BindService.LocalBinder binder=(BindService.LocalBinder)service;            mService=binder.getService();        }        @Override        public void onServiceDisconnected(ComponentName name) {        }    };}

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