android 主件之 Service

/Files/tt_mc/MyService.rar

 

一、Service的概念

Service是Android程序中四大基础组件之一，它和Activity一样都是Context的子类，只不过它没有UI界面，是在后台运行的组件。

二、Service的生命周期

Service对象不能自己启动，需要通过某个Activity、Service或者其他Context对象来启动。启动的方法有两种，Context.startService和Context.bindService()。两种方式的生命周期是不同的，具体如下所示。

使用context.startService() 启动Service是会会经历:
context.startService()  ->onCreate()- >onStart()->Service running
context.stopService() | ->onDestroy() ->Service stop 
 
如果Service还没有运行，则android先调用onCreate()然后调用onStart()；如果Service已经运行，则只调用onStart()，所以一个Service的onStart方法可能会重复调用多次。 
 
stopService的时候直接onDestroy，如果是调用者自己直接退出而没有调用stopService的话，Service会一直在后台运行。该Service的调用者再启动起来后可以通过stopService关闭Service。
 
所以调用startService的生命周期为：onCreate --> onStart(可多次调用) --> onDestroy
 
使用使用context.bindService()启动Service会经历：
context.bindService()->onCreate()->onBind()->Service running
onUnbind() -> onDestroy() ->Service stop
 
onBind将返回给客户端一个IBind接口实例，IBind允许客户端回调服务的方法，比如得到Service运行的状态或其他操作。这个时候把调用者（Context，例如Activity）会和Service绑定在一起，Context退出了，Srevice就会调用onUnbind->onDestroy相应退出。 
      
所以调用bindService的生命周期为：onCreate --> onBind(只一次，不可多次绑定) --> onUnbind --> onDestory。
 
在Service每一次的开启关闭过程中，只有onStart可被多次调用(通过多次startService调用)，其他onCreate，onBind，onUnbind，onDestory在一个生命周期中只能被调用一次。

使用context.startService()

 

public class MyService extends Activity implements OnClickListener {
    /** Called when the activity is first created. */
    Button buttonStart, buttonStop,buttonBind,buttonUnbind,buttonCount;
    private static final String TAG = "ServicesDemo"; 
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        buttonStart = (Button) findViewById(R.id.bt1);   
        buttonStop = (Button) findViewById(R.id.bt2);   
        buttonBind = (Button) findViewById(R.id.bt3);   
        buttonUnbind = (Button) findViewById(R.id.bt4);
        buttonCount = (Button) findViewById(R.id.bt5);
         
        buttonStart.setOnClickListener(this);   
        buttonStop.setOnClickListener(this); 
        buttonBind.setOnClickListener(this);   
        buttonUnbind.setOnClickListener(this);
        buttonCount.setOnClickListener(this);
        
       
    }

    //////////////////////
    //通过ServiceConnection的内部类实现来连接Service和Activity
    ///////////////////////
    
    private ICountService countService=null;
    
    private ServiceConnection serviceConnection = new ServiceConnection() {

        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            countService = (ICountService) service;
            Log.v("CountService", "on serivce connected, count is "
                    + countService.getCount());
        }

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

    };

    
    
    @Override
    public void onClick(View v) {
        switch (v.getId()) {   
         case R.id.bt1:   
           Log.d(TAG, "onClick: starting srvice"); 
         //activity传递值给service，service里的onStart()方法有个intent参数，可以接收到activity传递的值
           Intent intent1= new Intent();
           Bundle bundle1=new Bundle();
           bundle1.putString("activity-to-service","i come from activity");
           intent1.putExtras(bundle1);   
           intent1.setClass(this, CountService.class);
           this.startService(intent1);
           break;   
         case R.id.bt2:   
           Log.d(TAG, "onClick: stopping srvice");   
           this.stopService(new Intent(this, CountService.class));   
           break;  
         case R.id.bt3:   
               Log.d(TAG, "onClick: bind srvice"); 
               //bindservice启动的时候不会调用onstart方法
               //activity传递值给service，service里的onbind()方法有个intent参数，可以接收到activity传递的值
               Intent intent2= new Intent();
               Bundle bundle2=new Bundle();
               bundle2.putString("activity-to-bindservice","i come from activity");
               intent2.putExtras(bundle2);   
               intent2.setClass(this, BindCountService.class);
               this.bindService(intent2,this.serviceConnection, BIND_AUTO_CREATE);   
               break; 
         case R.id.bt4:   
               Log.d(TAG, "onClick: unbind srvice");   
               this.unbindService(serviceConnection);   
               break; 
         case R.id.bt5:   
             //随时和service通信，让activity获取到service里count的值是多少
               if(countService!=null)
               Log.d(TAG, "onClick: getCount="+countService.getCount());   
               break; 
         }   
    }
    
}

public class CountService extends Service{

    private boolean threadDisable;
    private String activityValue=null;
    private int count;

    @Override
    public IBinder onBind(Intent intent) {
        Log.v("CountService", "on bind");
        return null;
    }

    @Override
    public void onCreate() {
        super.onCreate();
        Log.v("CountService", "on create");
        new Thread(new Runnable() {

            @Override
            public void run() {
                while (!threadDisable) {
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                    }
                    count++;
                    Log.v("CountService", "Count is " + count);
                }
            }
        }).start();
    }

    
    @Override
    public void onRebind(Intent intent) {
        // TODO Auto-generated method stub
        super.onRebind(intent);
        Log.v("CountService", "on rebind");
    }

    @Override
    public void onStart(Intent intent, int startId) {
        // TODO Auto-generated method stub
        super.onStart(intent, startId);
        Log.v("CountService", "on start");
        //接收activity传递过来的值
        Bundle b=intent.getExtras();
        activityValue=b.getString("activity-to-service");
        Log.v("CountService", activityValue);
    }

    @Override
    public boolean onUnbind(Intent intent) {
        // TODO Auto-generated method stub
        Log.v("CountService", "on unbind");
        return super.onUnbind(intent);
        
    }
    
    

    @Override
    public void onDestroy() {
        super.onDestroy();
        this.threadDisable = true;
        Log.v("CountService", "on destroy");
    }

    public int getCount() {
        return count;
    }

    

}

 

使用context.bindService()

public interface ICountService {

    public abstract int getCount();
} 

public class BindCountService extends Service  {

    private int count;
    private boolean threadDisable;
    private String activityValue=null;
    
    @Override
    public IBinder onBind(Intent intent) {
        // TODO Auto-generated method stub
        Log.v("BindCountService", "on bind");
        //接收activity传递过来的值
        Bundle b=intent.getExtras();
        activityValue=b.getString("activity-to-bindservice");
        Log.v("BindCountService", activityValue);
        return serviceBinder;
    }

    private ServiceBinder serviceBinder=new ServiceBinder();
    
    public class ServiceBinder extends Binder implements ICountService{
        @Override
        public int getCount() {
            return count;
        }
    }
    
    @Override
    public void onCreate() {
        super.onCreate();
        Log.v("BindCountService", "on create");
        new Thread(new Runnable() {

            @Override
            public void run() {
                while (!threadDisable) {
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                    }
                    count++;
                    Log.v("BindCountService", "Count is " + count);
                }
            }
        }).start();
    }

    
     @Override
        public void onRebind(Intent intent) {
            // TODO Auto-generated method stub
            super.onRebind(intent);
            Log.v("BindCountService", "on rebind");
        }

        @Override
        public void onStart(Intent intent, int startId) {
            // TODO Auto-generated method stub
            super.onStart(intent, startId);
            Log.v("BindCountService", "on start");
        }

        @Override
        public boolean onUnbind(Intent intent) {
            // TODO Auto-generated method stub
            Log.v("BindCountService", "on unbind");
            return super.onUnbind(intent);
            
        }
    
    
    @Override
    public void onDestroy() {
        super.onDestroy();
        this.threadDisable = true;
        Log.v("BindCountService", "on destroy");
    }

    




}