Report work status

This guide shows you how to report the status of a work request run in a background service to the component that sent the request. This allows you, for example, to report the status of the request in an Activity object's UI. The recommended way to send and receive status is to use a LocalBroadcastManager, which limits broadcast Intentobjects to components in your own app.

翻译:report work status 一般都用LocalBroadcastManager

 

Report status from a JobIntentService

To send the status of a work request in an JobIntentService to other components, first create an Intent that contains the status in its extended data. As an option, you can add an action and data URI to this Intent.

Next, send the Intent by calling LocalBroadcastManager.sendBroadcast(). This sends the Intent to any component in your application that has registered to receive it. To get an instance of LocalBroadcastManager, callgetInstance().

翻译：创建intent，用LocalBroadcastManager来发给应用内的组件

 

public final class Constants { ... // Defines a custom Intent action public static final String BROADCAST_ACTION = "com.example.android.threadsample.BROADCAST"; ... // Defines the key for the status "extra" in an Intent public static final String EXTENDED_DATA_STATUS = "com.example.android.threadsample.STATUS"; ... } public class RSSPullService extends JobIntentService { ... /* * 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); ... }

The next step is to handle the incoming broadcast Intent objects in the component that sent the original work request.

翻译：下一步是在组件内处理Intent

 

Receive status broadcasts from a JobIntentService

To receive broadcast Intent objects, use a subclass of BroadcastReceiver. In the subclass, implement theBroadcastReceiver.onReceive() callback method, which LocalBroadcastManager invokes when it receives an Intent. LocalBroadcastManager passes the incoming Intent to BroadcastReceiver.onReceive().

// Broadcast receiver for receiving status updates from the IntentService. private class DownloadStateReceiver extends BroadcastReceiver { // Called when the BroadcastReceiver gets an Intent it's registered to receive @Override public void onReceive(Context context, Intent intent) { ... /* * Handle Intents here. */ ... } }

Once you've defined the BroadcastReceiver, you can define filters for it that match specific actions, categories, and data. To do this, create an IntentFilter. This first snippet shows how to define the filter:

翻译：定义intent filter来匹配action,categories,data

// Class that displays photos public class DisplayActivity extends FragmentActivity { ... public void onCreate(Bundle stateBundle) { ... super.onCreate(stateBundle); ... // The filter's action is BROADCAST_ACTION IntentFilter statusIntentFilter = new IntentFilter( Constants.BROADCAST_ACTION); // Adds a data filter for the HTTP scheme statusIntentFilter.addDataScheme("http"); ...

To register the BroadcastReceiver and the IntentFilter with the system, get an instance ofLocalBroadcastManager and call its registerReceiver() method. This next snippet shows how to register the BroadcastReceiver and its IntentFilter:

翻译：注册广播以及其IntentFilter

// Instantiates a new DownloadStateReceiver DownloadStateReceiver downloadStateReceiver = new DownloadStateReceiver(); // Registers the DownloadStateReceiver and its intent filters LocalBroadcastManager.getInstance(this).registerReceiver( downloadStateReceiver, statusIntentFilter);

A single BroadcastReceiver can handle more than one type of broadcast Intent object, each with its own action. This feature allows you to run different code for each action, without having to define a separate BroadcastReceiverfor each action. To define another IntentFilter for the same BroadcastReceiver, create the IntentFilter and repeat the call to registerReceiver(). For example:

翻译：一个BroadcastReceiver可以多用

/* * Instantiates a new action filter. * No data filter is needed. */ statusIntentFilter = new IntentFilter(Constants.ACTION_ZOOM_IMAGE); // Registers the receiver with the new filter LocalBroadcastManager.getInstance(this).registerReceiver( downloadStateReceiver, statusIntentFilter);

 

Sending an broadcast Intent doesn't start or resume an Activity. The BroadcastReceiver for an Activityreceives and processes Intent objects even when your app is in the background, but doesn't force your app to the foreground. If you want to notify the user about an event that happened in the background while your app was not visible, use a Notification. Never start an Activity in response to an incoming broadcast Intent.

翻译：

发广播不会让Activity resume.也不会让app 变成前台应用，如果想提醒用户就发广播吧。

另外，不要在广播里面开启Activity.