杭州手机网站制作公司,西安计算机培训机构,杭州定制网站公司,网站建设费用有哪些原文地址#xff1a;https://developer.android.com/training/run-background-service/report-status.html
这节课主要学习如何将IntentService中的执行结果返回给请求点。一种推荐的方式就是使用 LocalBroadcastManager来实现#xff0c;它会将所广播的Intent限制在APP内部…原文地址https://developer.android.com/training/run-background-service/report-status.html
这节课主要学习如何将IntentService中的执行结果返回给请求点。一种推荐的方式就是使用 LocalBroadcastManager来实现它会将所广播的Intent限制在APP内部。
发送IntentService的处理结果
为了可以将IntentService的处理结果发送给其它组件首先需要创建一个Intent对象并将执行结果放入该Intent内。
接下来要做的就是将刚才创建好的Intent通过LocalBroadcastManager.sendBroadcast()发送出去。但凡是对该Intent注册了的那么发送该Intent都会收到结果。可以通过getInstance()获取LocalBroadcastManager的实例。
例子如下
public final class Constants {...// Defines a custom Intent actionpublic static final String BROADCAST_ACTION com.example.android.threadsample.BROADCAST;...// Defines the key for the status extra in an Intentpublic static final String EXTENDED_DATA_STATUS com.example.android.threadsample.STATUS;...
}
public class RSSPullService extends IntentService {
.../** Creates a new Intent containing a Uri object* BROADCAST_ACTION is a custom Intent action*/Intent localIntent new Intent(Constants.BROADCAST_ACTION)// Puts the status into the Intent.putExtra(Constants.EXTENDED_DATA_STATUS, status);// Broadcasts the Intent to receivers in this app.LocalBroadcastManager.getInstance(this).sendBroadcast(localIntent);
...
}
下一步就是如何处理接收到的Intent对象了。
接收IntentService的处理结果
如果需要接收广播出来的Intent那么就需要用到BroadcastReceiver了。在BroadcastReceiver的实现类中重写onReceive()方法。当LocalBroadcastManager将相应的Intent对象广播出来后那么该方法就会被自动回调。
举个例子
// Broadcast receiver for receiving status updates from the IntentService
private class ResponseReceiver extends BroadcastReceiver
{// Prevents instantiationprivate DownloadStateReceiver() {}// Called when the BroadcastReceiver gets an Intent its registered to receivepublic void onReceive(Context context, Intent intent) {
.../** Handle Intents here.*/
...}
}
一旦定义好了BroadcastReceiver那么就可以为其定义指定的意图过滤器了。要做到这些需要创建一个IntentFilter。下面的代码演示了如何定义一个过滤器
// Class that displays photos
public class DisplayActivity extends FragmentActivity {...public void onCreate(Bundle stateBundle) {...super.onCreate(stateBundle);...// The filters action is BROADCAST_ACTIONIntentFilter mStatusIntentFilter new IntentFilter(Constants.BROADCAST_ACTION);// Adds a data filter for the HTTP schememStatusIntentFilter.addDataScheme(http);为了将BroadcastReceiver以及IntentFilter注册到系统需要先获取LocalBroadcastManager的实例然后再调用它的registerReceiver()方法。下面的代码演示了这个过程 // Instantiates a new DownloadStateReceiverDownloadStateReceiver mDownloadStateReceiver new DownloadStateReceiver();// Registers the DownloadStateReceiver and its intent filtersLocalBroadcastManager.getInstance(this).registerReceiver(mDownloadStateReceiver,mStatusIntentFilter);...
BroadcastReceiver可以同时处理多种类型的Intent对象这项特性可以为每种Action定义不同的代码而不需要专门去定义BroadcastReceiver。为同一个BroadcastReceiver定义另外的IntentFilter只需再创建一个IntentFilter然后再次注册一下就好 /** Instantiates a new action filter.* No data filter is needed.*/statusIntentFilter new IntentFilter(Constants.ACTION_ZOOM_IMAGE);...// Registers the receiver with the new filterLocalBroadcastManager.getInstance(getActivity()).registerReceiver(mDownloadStateReceiver,mIntentFilter);
发送广播Intent并不会启动或者恢复Activity。就算是APP处于挂起状态(处于后台)也同样会接收到Intent。如果APP处于挂起状态的话有任务完成需要通知到用户那么可以使用Notification做到。绝不要启动Activity来响应接收到的Intent广播。
