Android_Service详解

Android_Service详解

一、Service简介：

Service组件是与Activity组件最相似的组件。Service组件也是可执行的程序，有自己的生命周期。



开发Service的步骤：
1、定义一个继承Service的子类。
2、配置Service。

二、Service的生命周期：

context.startService() ->onCreate()- >onStart()->Service running--调用context.stopService() ->onDestroy()

context.bindService()->onCreate()->onBind()->Service running--调用>onUnbind() -> onDestroy()

下面通过一个实例进行说明：

public class MyService extends Service {
	private final String TAG = "MyService";

	@Override
	public void onCreate() {
		// TODO Auto-generated method stub
		super.onCreate();
		Log.i(TAG, "--->>onCreate");
	}

	//onStartCommand方法中链接网络获取数据，关闭service服务
	@Override
	public int onStartCommand(Intent intent, int flags, int startId) {
		// TODO Auto-generated method stub
		Log.i(TAG, "--->>onStartCommand-->>"+intent.getStringExtra("name"));
		return super.onStartCommand(intent, flags, startId);
	}

	@Override
	public IBinder onBind(Intent arg0) {
		// TODO Auto-generated method stub
		return null;
	}
    //资源的释放
	@Override
	public void onDestroy() {
		// TODO Auto-generated method stub
		Log.i(TAG, "--->>onDestroy");
		super.onDestroy();
	}
}

public class MainActivity extends Activity {
	private Button start;
	private Button stop;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		start = (Button) this.findViewById(R.id.button1);
		stop = (Button) this.findViewById(R.id.button2);
		start.setOnClickListener(new View.OnClickListener() {
			@Override
			public void onClick(View arg0) {
				// TODO Auto-generated method stub
				Intent intent = new Intent(MainActivity.this, MyService.class);
				intent.putExtra("name", "jack");
				startService(intent);
			}
		});
		stop.setOnClickListener(new View.OnClickListener() {
			@Override
			public void onClick(View v) {
				// TODO Auto-generated method stub
				Intent intent = new Intent(MainActivity.this, MyService.class);
				stopService(intent);
			}
		});
	}

	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.main, menu);
		return true;
	}

}

三、绑定Service并实现通信：

如果Service和访问者之间需要进行方法调用和数据交换，则应该使用bindService()和unbindService()方法启动、关闭Service。

Context的bindService(Intent service,ServiceConnection conn,int flags)方法:

service:指定要启动的Service。
conn：该参数是一个ServiceConnection对象，用于监听访问者与Service之间的连接状况。
flags：指定绑定时是否自动创建Service。

下面有一个实例进行说明：

public class BindService extends Service
{
	private int count;
	private boolean quit;
	// 定义onBinder方法所返回的对象
	private MyBinder binder = new MyBinder();
	// 通过继承Binder来实现IBinder类
	public class MyBinder extends Binder //①
	{
		public int getCount()
		{
			// 获取Service的运行状态：count
			return count;
		}
	}
	// 必须实现的方法，绑定该Service时回调该方法
	@Override
	public IBinder onBind(Intent intent)
	{
		System.out.println("Service is Binded");
		// 返回IBinder对象
		return binder;
	}
	// Service被创建时回调该方法。
	@Override
	public void onCreate()
	{
		super.onCreate();
		System.out.println("Service is Created");
		// 启动一条线程、动态地修改count状态值
		new Thread()
		{
			@Override
			public void run()
			{
				while (!quit)
				{
					try
					{
						Thread.sleep(1000);
					}
					catch (InterruptedException e)
					{
					}
					count++;
				}
			}
		}.start();
	}
	// Service被断开连接时回调该方法
	@Override
	public boolean onUnbind(Intent intent)
	{
		System.out.println("Service is Unbinded");
		return true;
	}
	// Service被关闭之前回调该方法。
	@Override
	public void onDestroy()
	{
		super.onDestroy();
		this.quit = true;
		System.out.println("Service is Destroyed");
	}
}

public class BindServiceTest extends Activity
{
	Button bind, unbind, getServiceStatus;
	// 保持所启动的Service的IBinder对象
	BindService.MyBinder binder;
	// 定义一个ServiceConnection对象
	private ServiceConnection conn = new ServiceConnection()
	{
		// 当该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--");
			// 获取Service的onBind方法所返回的MyBinder对象
			binder = (BindService.MyBinder) service; //①
		}

		// 当该Activity与Service断开连接时回调该方法
		@Override
		public void onServiceDisconnected(ComponentName name)
		{
			System.out.println("--Service Disconnected--");
		}
	};

	@Override
	public void onCreate(Bundle savedInstanceState)
	{
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		// 获取程序界面中的start、stop、getServiceStatus按钮
		bind = (Button) findViewById(R.id.bind);
		unbind = (Button) findViewById(R.id.unbind);
		getServiceStatus = (Button) findViewById(R.id.getServiceStatus);
		// 创建启动Service的Intent
		final Intent intent = new Intent();
		// 为Intent设置Action属性
		intent.setAction("org.crazyit.service.BIND_SERVICE");
		bind.setOnClickListener(new OnClickListener()
		{
			@Override
			public void onClick(View source)
			{
				// 绑定指定Serivce
				bindService(intent, conn, Service.BIND_AUTO_CREATE);
			}
		});
		unbind.setOnClickListener(new OnClickListener()
		{
			@Override
			public void onClick(View source)
			{
				// 解除绑定Serivce
				unbindService(conn);
			}
		});
		getServiceStatus.setOnClickListener(new OnClickListener()
		{
			@Override
			public void onClick(View source)
			{
				// 获取、并显示Service的count值
				Toast.makeText(BindServiceTest.this,
					"Serivce的count值为：" + binder.getCount(),
					Toast.LENGTH_SHORT).show(); //②
			}
		});
	}
}

四、IntentService的使用：

Service本身不会创建一个线程，因此Service不能处理耗时任务。
IntentService刚好弥补这一缺陷。

public class MyIntentService extends IntentService {

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

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

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

}

public class MainActivity extends Activity implements OnClickListener {

	private Button startIntentService;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		startIntentService = (Button) findViewById(R.id.start_intent_service);
		startIntentService.setOnClickListener(this);
	}

	@Override
	public void onClick(View v) {
		switch (v.getId()) {
		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;
		}
	}
}

五、跨进程调用Service(AIDL Service)

Android需要AIDL来定义远程接口。
AIDL的语法与java接口相似，但存在以下两点差异：

1、AIDL定义接口的源代码必须以.aidl结尾。
2、AIDL接口用到的数据类型除了基本类型外，其他类型全需要导包。

ICat.aidl

package org.husheng.service;

interface ICat
{
	String getColor();
	double getWeight();
}

AidlService.java

public class AidlService extends Service
{
	private CatBinder catBinder;
	Timer timer = new Timer();
	String[] colors = new String[]{
		"红色",
		"***",
		"黑色"
	};
	double[] weights = new double[]{
		2.3,
		3.1,
		1.58
	};
	private String color;
	private double weight;
	// 继承Stub，也就是实现额ICat接口，并实现了IBinder接口
	public class CatBinder extends Stub
	{
		@Override
		public String getColor() throws RemoteException
		{
			return color;
		}
		@Override
		public double getWeight() throws RemoteException
		{
			return weight;
		}
	}
	@Override
	public void onCreate()
	{
		super.onCreate();
		catBinder = new CatBinder();
		timer.schedule(new TimerTask()
		{
			@Override
			public void run()
			{
				// 随机地改变Service组件内color、weight属性的值。
				int rand = (int)(Math.random() * 3);
				color = colors[rand];
				weight = weights[rand];
				System.out.println("--------" + rand);
			}
		} , 0 , 800);
	}
	@Override
	public IBinder onBind(Intent arg0)
	{
		/* 返回catBinder对象
		 * 在绑定本地Service的情况下，该catBinder对象会直接
		 * 传给客户端的ServiceConnection对象
		 * 的onServiceConnected方法的第二个参数；
		 * 在绑定远程Service的情况下，只将catBinder对象的代理
		 * 传给客户端的ServiceConnection对象
		 * 的onServiceConnected方法的第二个参数；
		 */
		return catBinder; //①
	}
	@Override
	public void onDestroy()
	{
		timer.cancel();
	}
}

AidlClient.java

public class AidlClient extends Activity
{
	private ICat catService;
	private Button get;
	EditText color, weight;
	private ServiceConnection conn = new ServiceConnection()
	{
		@Override
		public void onServiceConnected(ComponentName name
			, IBinder service)
		{
			// 获取远程Service的onBind方法返回的对象的代理
			catService = ICat.Stub.asInterface(service);
		}

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

	@Override
	public void onCreate(Bundle savedInstanceState)
	{
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		get = (Button) findViewById(R.id.get);
		color = (EditText) findViewById(R.id.color);
		weight = (EditText) findViewById(R.id.weight);
		// 创建所需绑定的Service的Intent
		Intent intent = new Intent();
		intent.setAction("org.crazyit.aidl.action.AIDL_SERVICE");
		// 绑定远程Service
		bindService(intent, conn, Service.BIND_AUTO_CREATE);
		get.setOnClickListener(new OnClickListener()
		{
			@Override
			public void onClick(View arg0)
			{
				try
				{
					// 获取、并显示远程Service的状态
					color.setText(catService.getColor());
					weight.setText(catService.getWeight() + "");
				}
				catch (RemoteException e)
				{
					e.printStackTrace();
				}
			}
		});
	}

	@Override
	public void onDestroy()
	{
		super.onDestroy();
		// 解除绑定
		this.unbindService(conn);
	}
}

六、总结：

掌握Service的用法。