我一直在学习“Pro
Android 2”一书.我正在研究一个由两个类组成的Service示例:BackgroundService.java和MainActivity.java. MainActivity声称(错误地?)它启动服务,如下面的Log.d调用输出到logcat所示:
public class MainActivity extends Activity { private static final String TAG = "MainActivity"; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); Log.d(TAG,"starting service"); Button bindBtn = (Button)findViewById(R.id.bindBtn); bindBtn.setonClickListener(new OnClickListener() { @Override public void onClick(View arg0) { Intent backgroundService = new Intent(MainActivity.this,com.marie.mainactivity.BackgroundService.class); startService(backgroundService); } }); Button unbindBtn = (Button)findViewById(R.id.unbindBtn); unbindBtn.setonClickListener(new OnClickListener() { @Override public void onClick(View arg0) { stopService(new Intent(MainActivity.this,BackgroundService.class)); } }); } }
令我困惑的是UI提供了两个按钮:Bind和UnBind,如上所示.但是根据documentation,如果onBind()如下所示返回null,表示你不想允许绑定.但是如上所示,(Bind按钮)的onClick()方法bindBtn.setonClickListener(新的OnClickListener()调用startService(backgroundService),它给出了这个错误:“无法启动服务Intent {cmp = com.marie.mainactivity / .BackgroundService }: 未找到”
public class BackgroundService extends Service { private notificationmanager notificationMgr; @Override public void onCreate() { super.onCreate(); notificationMgr = notificationmanager)getSystemService(NOTIFICATION_SERVICE); displayNotificationMessage("starting Background Service"); Thread thr = new Thread(null,new ServiceWorker(),"BackgroundService"); thr.start(); } class ServiceWorker implements Runnable { public void run() { // do background processing here... //stop the service when done... //BackgroundService.this.stopSelf(); } } @Override public void onDestroy() { displayNotificationMessage("stopping Background Service"); super.onDestroy(); } @Override public void onStart(Intent intent,int startId) { super.onStart(intent,startId); } @Override public IBinder onBind(Intent intent) { return null; } private void displayNotificationMessage(String message) { Notification notification = new Notification(R.drawable.note,message,System.currentTimeMillis()); PendingIntent contentIntent = PendingIntent.getActivity(this,new Intent(this,MainActivity.class),0); notification.setLatestEventInfo(this,"Background Service",contentIntent); notificationMgr.notify(R.id.app_notification_id,notification); } }
我不明白这个例子的意义.如果onBind()返回null,那么有一个Bind按钮(bindBtn)是什么意思?我认为重点是展示如何启动BackgroundService.但它似乎没有用,除非我遗漏了什么.
我应该添加我添加到我的AndroidManifest.xml:
<service android:name=".BackgroundService"></service>
如下:
<application android:icon="@drawable/icon" android:label="@string/app_name"> <activity android:name=".MainActivity" android:label="@string/app_name"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> <service android:name=".BackgroundService"></service> </activity> </application>
解决方法
从活动内部删除服务.它与应用程序中的活动处于同一级别.例如:
<application android:icon="@drawable/icon" android:label="@string/app_name"> <activity android:name=".MainActivity" 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=".BackgroundService"></service> </application>