Android应用开发笔记(5)：Android中的Service使用
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 } }
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>