Service的生命周期 (适用于2.1及以上)
1. 被startService的
无论是否有任何活动绑定到该Service,都在后台运行。onCreate(若需要) -> onStart(int id, Bundle args).  多次startService,则onStart调用多次,但不会创建多个Service实例,只需要一次stop。该Service一直后台运行,直到stopService或者自己的stopSelf()或者资源不足由平台结束。
2. 被bindService的
调用bindService绑定,连接建立服务一直运行。未被startService只是BindService,则onCreate()执行,onStart(int,Bundle)不被调用;这种情况下绑定被解除,平台就可以清除该Service(连接销毁后,会导致解除,解除后就会销毁)。
3. 被启动又被绑定
类似startService的生命周期,onCreate onStart都会调用。
4. 停止服务时
stopService时显式onDestroy()。或不再有绑定(没有启动时)时隐式调用。有bind情况下stopService()不起作用。
以下是一个简单的实现例子,某些部分需要配合logcat观察。
AcMain.java
- package jtapp.myservicesamples;
 - import android.app.Activity;
 - import android.content.ComponentName;
 - import android.content.Context;
 - import android.content.Intent;
 - import android.content.ServiceConnection;
 - import android.os.Bundle;
 - import android.os.IBinder;
 - import android.util.Log;
 - import android.view.View;
 - import android.view.View.OnClickListener;
 - import android.widget.Button;
 - import android.widget.Toast;
 - public class AcMain extends Activity implements OnClickListener {
 -        private static final String TAG = "AcMain";
 -        private Button btnStart;
 -        private Button btnStop;
 -        private Button btnBind;
 -        private Button btnExit;
 -        
 -        /** Called when the activity is first created. */
 -        @Override
 -        public void onCreate(Bundle savedInstanceState) {
 -              super.onCreate(savedInstanceState);
 -              setContentView(R.layout.main);
 -              
 -              findView();
 -        }
 -       
 -        private void findView() {
 -              btnStart = (Button) findViewById(R.id.Start);
 -              btnStop = (Button) findViewById(R.id.Stop);
 -              btnBind = (Button) findViewById(R.id.Bind);
 -              btnExit = (Button) findViewById(R.id.Exit);
 -              
 -              btnStart.setOnClickListener(this);
 -              btnStop.setOnClickListener(this);
 -              btnBind.setOnClickListener(this);
 -              btnExit.setOnClickListener(this);
 -        }
 -       
 -        @Override
 -        public void onClick(View v) {
 -              Intent intent = new Intent("jtapp.myservicesamples.myservice");
 -              switch(v.getId()) {
 -                    case R.id.Start:
 -                    startService(intent);
 -                    Toast.makeText(this, 
 -                    "myservice running " + MyService.msec/1000.0 + "s.", 
 -                    Toast.LENGTH_LONG).show();
 -                    break;
 -                    case R.id.Stop:
 -                    stopService(intent);
 -                    Toast.makeText(this,
 -                    "myservice running " + MyService.msec/1000.0 + "s.", 
 -                    Toast.LENGTH_LONG).show();
 -                    break;
 -                    case R.id.Bind:
 -                    bindService(intent, sc, Context.BIND_AUTO_CREATE);
 -                    break;
 -                    case R.id.Exit:
 -                    this.finish();
 -                    break;
 -              }
 -        }
 -        
 -        private MyService serviceBinder;
 -        
 -        private ServiceConnection sc = new ServiceConnection() {
 -              @Override
 -              public void onServiceDisconnected(ComponentName name) {
 -                    Log.d(TAG, "in onServiceDisconnected");
 -                    serviceBinder = null;
 -              }
 -              @Override
 -              public void onServiceConnected(ComponentName name, IBinder service) {
 -                    Log.d(TAG, "in onServiceConnected");
 -                    serviceBinder = ((MyService.MyBinder)service).getService();
 -              }
 -        };
 -       
 -        @Override
 -        protected void onDestroy() {
 -              //this.unbindService(sc);
 -              //this.stopService(
 -              // new Intent("jtapp.myservicesamples.myservice"));
 -              super.onDestroy();
 -        }
 - }
 
main.xml
- <?xml version="1.0" encoding="utf-8"?>
 - <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 -         android:orientation="vertical" android:layout_width="fill_parent"
 -         android:layout_height="fill_parent">
 -         <TextView android:layout_width="fill_parent"
 -                 android:layout_height="wrap_content" android:text="@string/hello" />
 -         <Button android:text="Start MyService" android:id="@+id/Start"
 -                 android:layout_width="wrap_content" android:layout_height="wrap_content"/>
 -         <Button android:text="Stop MyService" android:id="@+id/Stop"
 -                 android:layout_width="wrap_content" android:layout_height="wrap_content"/>
 -         <Button android:text="Bind MyService" android:id="@+id/Bind"
 -                 android:layout_width="wrap_content" android:layout_height="wrap_content"/>
 -         <Button android:text="Exit AcMain" android:id="@+id/Exit"
 -                 android:layout_width="wrap_content" android:layout_height="wrap_content"/>
 - </LinearLayout>
 
MyService.java
- package jtapp.myservicesamples;
 - import android.app.Service;
 - import android.content.Intent;
 - import android.os.Binder;
 - import android.os.IBinder;
 - import android.util.Log;
 - public class MyService extends Service {
 -        private static final String TAG = "MyService";
 -        public static long msec = 0;
 -        private boolean bThreadRunning = true;
 -        
 -        
 -        private final IBinder binder = new MyBinder();
 -        public class MyBinder extends Binder {
 -              MyService getService() {
 -                    return MyService.this;
 -              }
 -        }
 -        @Override
 -        public IBinder onBind(Intent intent) {
 -              return binder;
 -        }
 -       
 -        @Override
 -        public void onCreate() {
 -              new Thread(new Runnable(){
 -                    @Override
 -                    public void run() {
 -                          while (bThreadRunning) {
 -                                try {
 -                                      Thread.sleep(100);
 -                                } catch (InterruptedException e) {
 -                                }
 -                                Log.i(TAG, "myservice running " + (msec+=100) + "ms.");
 -                          }
 -                    }
 -              }).start();
 -        }
 -       
 -        @Override
 -        public void onDestroy() {
 -              bThreadRunning = false;
 -              super.onDestroy(); // 可以不用
 -        }
 -       
 - }
 
复制代码
AnndroidManifest.xml
- <?xml version="1.0" encoding="utf-8"?>
 - <manifest xmlns:android="http://schemas.android.com/apk/res/android"
 -         package="jtapp.myservicesamples" android:versionCode="1"
 -         android:versionName="1.0">
 -         <application android:icon="@drawable/icon" android:label="@string/app_name"
 -                 android:debuggable="true">
 -                 <activity android:name=".AcMain" android:label="@string/app_name">
 -                         <intent-filter>
 -                                 <action android:name="android.intent.action.MAIN" />
 -                                 <category android:name="android.intent.category.LAUNCHER" />
 -                         </intent-filter>
 -                 </activity>
 -                 <service android:name="MyService">
 -                         <intent-filter>
 -                                 <action android:name="jtapp.myservicesamples.myservice"></action>
 -                         </intent-filter>
 -                 </service>
 -         </application>
 - </manifest>