每日日报2021 5/22

Context的bindService方法：

• ServiceConnection对象:监听访问者与Service间的连接情况,如果成功连接,回调 onServiceConnected(),如果异常终止或者其他原因终止导致Service与访问者断开 连接则回调onServiceDisconnected方法,调用unBindService()不会调用该方法!
• onServiceConnected方法中有一个IBinder对象,该对象即可实现与被绑定Service 之间的通信!我们再开发Service类时,默认需要实现IBinder onBind()方法,该方法返回的 IBinder对象会传到ServiceConnection对象中的onServiceConnected的参数,我们就可以 在这里通过这个IBinder与Service进行通信Step 1:在自定义的Service中继承Binder,实现自己的IBinder对象

Step 2:通过onBind( )方法返回自己的IBinder对象
Step 3:在绑定该Service的类中定义一个ServiceConnection对象,重写两个方法, onServiceConnected和onDisconnected！然后直接读取IBinder传递过来的参数即可!

那么好了,接下来就是写代码验证了,这里的话我们定义一个用来计时的Service, 然后来演示BindService的用法以及方法调用流程!代码比较简单,不解释了!

TestService2.java:

public class TestService2 extends Service {  
    private final String TAG = "TestService2";  
    private int count;  
    private boolean quit;  
      
    //定义onBinder方法所返回的对象  
    private MyBinder binder = new MyBinder();  
    public class MyBinder extends Binder  
    {  
        public int getCount()  
        {  
            return count;  
        }  
    }  
      
    //必须实现的方法,绑定改Service时回调该方法  
    @Override  
    public IBinder onBind(Intent intent) {  
        Log.i(TAG, "onBind方法被调用!");  
        return binder;  
    }  
  
    //Service被创建时回调  
    @Override  
    public void onCreate() {  
        super.onCreate();  
        Log.i(TAG, "onCreate方法被调用!");  
        //创建一个线程动态地修改count的值  
        new Thread()  
        {  
            public void run()   
            {  
                while(!quit)  
                {  
                    try  
                    {  
                        Thread.sleep(1000);  
                    }catch(InterruptedException e){e.printStackTrace();}  
                    count++;  
                }  
            };  
        }.start();  
          
    }  
      
    //Service断开连接时回调  
    @Override  
    public boolean onUnbind(Intent intent) {  
        Log.i(TAG, "onUnbind方法被调用!");  
        return true;  
    }  
      
    //Service被关闭前回调  
    @Override  
    public void onDestroy() {  
        super.onDestroy();  
        this.quit = true;  
        Log.i(TAG, "onDestroyed方法被调用!");  
    }  
      
    @Override  
    public void onRebind(Intent intent) {  
        Log.i(TAG, "onRebind方法被调用!");  
        super.onRebind(intent);  
    }  
}

在AndroidManifest.xml中对Service组件进行注册:

<service android:name=".TestService2" android:exported="false">  
        <intent-filter>  
            <action android:name="com.jay.example.service.TEST_SERVICE2"/>  
        </intent-filter>  
</service>

MainActivity.java:

public class MainActivity extends Activity {  
  
    private Button btnbind;  
    private Button btncancel;  
    private Button btnstatus;  
      
    //保持所启动的Service的IBinder对象,同时定义一个ServiceConnection对象  
    TestService2.MyBinder binder;  
    private ServiceConnection conn = new ServiceConnection() {  
          
        //Activity与Service断开连接时回调该方法  
        @Override  
        public void onServiceDisconnected(ComponentName name) {  
            System.out.println("------Service DisConnected-------");  
        }  
          
        //Activity与Service连接成功时回调该方法  
        @Override  
        public void onServiceConnected(ComponentName name, IBinder service) {  
            System.out.println("------Service Connected-------");  
            binder = (TestService2.MyBinder) service;  
        }  
    };  
      
    @Override  
    protected void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        setContentView(R.layout.activity_main);  
        btnbind = (Button) findViewById(R.id.btnbind);  
        btncancel = (Button) findViewById(R.id.btncancel);  
        btnstatus  = (Button) findViewById(R.id.btnstatus);  
        final Intent intent = new Intent();  
        intent.setAction("com.jay.example.service.TEST_SERVICE2");  
        btnbind.setOnClickListener(new OnClickListener() {            
            @Override  
            public void onClick(View v) {  
                //绑定service  
                bindService(intent, conn, Service.BIND_AUTO_CREATE);                  
            }  
        });  
          
        btncancel.setOnClickListener(new OnClickListener() {  
            @Override  
            public void onClick(View v) {  
                //解除service绑定  
                unbindService(conn);                  
            }  
        });  
          
        btnstatus.setOnClickListener(new OnClickListener() {  
            @Override  
            public void onClick(View v) {  
                Toast.makeText(getApplicationContext(), "Service的count的值为:"  
                        + binder.getCount(), Toast.LENGTH_SHORT).show();  
            }  
        });  
    }  
}